Justipen--the Japan U.s. Theory Institute For Physics With Exotic Nuclei

Transcript

Nuclear Physics News Volume 18/No. 4 Nuclear Physics News is published on behalf of the Nuclear Physics European Collaboration Committee (NuPECC), an Expert Committee of the European Science Foundation, with colleagues from Europe, America, and Asia. Editor: Gabriele-Elisabeth Körner Editorial Board T. Bressani, Torino R. F. Casten, Yale P.-H. Heenen, Brussels (Chairman) J. Kvasil, Prague M. Lewitowicz, Caen S. Nagamiya, Tsukuba A. Shotter, Vancouver H. Ströher, Jülich T. J. Symons, Berkeley C. Trautmann, Darmstadt Editorial Office: Physikdepartment, E12, Technische Universitat München, 85748 Garching, Germany, Tel: +49 89 2891 2293, +49 172 89 15011, Fax: +49 89 2891 2298, E-mail: [email protected] Correspondents Argentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Leeb, Vienna; Belgium: G. Neyens, Leuven; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou, TRIUMF; K, Sharma, Manitoba; C. Svensson, Guelph: China: W. Zhan, Lanzhou; Croatia: R. Caplar, Zagreb; Czech Republic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Århus; Finland: M. Leino, Jyväskylä; France: G. De France, GANIL Caen; M. MacCormick, IPN Orsay; Germany: K. Langanke, GSI Darmstadt; U. Wiedner, Bochum; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen; India: D. K. Avasthi, New Delhi; Israel: N. Auerbach, Tel Aviv; Italy: M. Ripani, Genova; L. Corradi, Legnaro; Japan: T. Motobayashi, RIKEN; Mexico: J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen, Bergen; Poland: B. Fornal, Cracow; Portugal: M. Fernanda Silva, Sacavém; Romania: V. Zamfir, Bucharest; Russia: Yu. Novikov, St. Petersburg; Serbia: S. Jokic, Belgrade; South Africa: S. Mullins, Cape Town; Spain: B. Rubio, Valencia; Sweden: J. Nyberg, Uppsala; Switzerland: K. Kirch, PSI Villigen; United Kingdom: P. Regan, Surrey; USA: D. Geesaman, Argonne; D. W. Higinbotham, Jefferson Lab; M. Thoenessen, Michigan State Univ.; H. G. Ritter, Lawrence Berkeley Laboratory; G. Miller, Seattle. Nuclear Physics News ISSN 1050-6896 Advertising Manager Maureen M. Williams, 28014 N. 123rd Lane, Peoria, AZ 85383, USA Tel: +1 623 544 1698 Fax: +1 623 544 1699 E-mail: [email protected] Circulation and Subscriptions Taylor & Francis Inc. 325 Chestnut Street 8th Floor Philadelphia, PA 19106, USA Tel: +1 215 625 8900 Fax: +1 215 625 8914 Subscriptions Nuclear Physics News is supplied free of charge to nuclear physicists from contributing countries upon request. In addition, the following subscriptions are available: Volume 18 (2008), 4 issues Personal: $93 USD, £55 GBP, €74 Euro Institution: $768 USD, £465 GBP, €614 Euro Copyright © 2008 Taylor & Francis Group, LLC. Reproduction without permission is prohibited. All rights reserved. The opinions expressed in NPN are not necessarily those of the editors or publishers. Vol. 18, No. 4, 2008, Nuclear Physics News 1 Nuclear Physics News Volume 18/No. 4 Contents Editorial .............................................................................................................................................................. 3 Laboratory Portrait The Nuclear Physics Laboratory at CEA DAM Ile-de-France by Eric Bauge .................................................................................................................................................. 5 Feature Article Deep Underground Laboratories—Somewhere Quiet in the Universe by Neil Spooner ............................................................................................................................................. 13 Facilities and Methods JUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei by David J. Dean ........................................................................................................................................... 21 Compass and the Nucleon Spin Puzzle by Bradamante............................................................................................................................................... 26 Impact and Applications Industrial PET at Birmingham by David Parker ............................................................................................................................................. 33 Meeting Reports The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13 by Kris Heyde ................................................................................................................................................. 37 Hadron Physics Summer School 2008 by Frank Goldenbaum .................................................................................................................................... 38 News and Views ................................................................................................................................................ 40 Calendar ............................................................................................................................................................ 44 Cover illustration: 2 Nuclear Physics News, Vol. 18, No. 4, 2008 editorial OECD Global Science Forum Report on Nuclear Physics Globally about $2B is spent annually for Nuclear Physics research. Over 13,000 scientists, engineers, and students involved in research carried out primarily at the 90 major accelerator facilities with user programs, but also at a range of smaller, specialized facilities that provide for national needs. This is a truly enormous human endeavor and it is sobering to think that our science justifies such a commitment of resources. This rather startling insight is one of a number of interesting results from the efforts of the Working Group on Nuclear Physics, established by the Global Science Forum of the OECD (Organisation for Economic Co-operation and Development). Their report was published earlier this year and can be accessed at www.oecd.org/sti/gsf. The Global Science Forum provides a venue for communication between senior science policy officials and the Forum’s activities produce findings and recommendations for action by governments, international organizations, and the scientific community. The last report on Nuclear Physics was by the Working Group on Nuclear Physics (1996– 1999) chaired by Bernard Frois and highlighted the enormous potential that the development of radioactive beam facilities would provide for nuclear physics research. That report provided the background for the last round of large-scale investment in our field. The present Working Group was established in 2006 and was chaired by Dennis Kovar. Its recommendations set the backdrop against which the funding agencies will plan investment in our field for the next decade. The report draws attention to the major advances that have occurred in the decade since the last report was published, highlighting of particular interest: the observation of a new state of matter in the form of the QGP, the confirmation from solar neutrino measurements that neutrinos have mass, and the explosion of knowledge regarding exotic nuclear structure and nuclear astrophysics made possible by the advent of radioactive beam facilities. The working group assessment for the next decade is equally bright, with the main challenges summarized in a series of questions: Is QCD the complete theory of the strong interaction? What are the phases of nuclear matter? What is the structure of nuclear matter? What is the role of nuclei in shaping the evolution of the universe? What physics is there beyond the standard model? The section of the report that will perhaps be of most interest to our funding agencies (and so impact directly on our ambitions as scientists) relates to international cooperation and strategic planning. The working group observes that international cooperation has long been the norm in our science and as evidence for this notes the large external user presence at major national facilities (for example GSI 40%, RHIC 50%, CEBAF 40%, and TRIUMF 66%). The report strongly endorses this internationalization of our science and recommends that “free and open access to beam usage should continue to be the international mode of operation for nuclear physics facilities.” The report also notes that our community has effectively developed a worldwide roadmap for the development of the subject. Particularly important in this regard are the periodic Long Range Plans prepared in Europe by NuPECC (www.nupecc.org/pubs/lrp03/long_ range_plan_2004.pdf) and in the United States by NSAC (www.sc.doe. gov/np/nsac/nsac.html). The report finds that “this global roadmap reflects a high degree of coordination in optimizing the available resources for the world-wide nuclear physics programme.” The working group suggests that a mechanism should be established to review this global roadmap on a regular basis and proposes that WG9, the IUPAP Working Group on Nuclear Physics, might take on this role. As noted earlier, these periodic OECD reports do exert influence over the direction in which our field develops, because they are reports commissioned by, and accepted by, our funding agencies. For this reason they form valuable reading for the research community. Indeed, the present report has already had noticeable effects. Colleagues in Asia have recognized the benefits of regional planning and are in the process of establishing a version of NuPECC that will allow Asian countries to extend cooperation and The views expressed here do not represent the views and policies of NuPECC except where explicitly identified. Vol. 18, No. 4, 2008, Nuclear Physics News 3 editorial develop regional plans, and WG9 has already discussed the proposal that they take on the role of preparing and updating a global roadmap for the field based on the regional planning. Such moves are timely, for while our field is currently at a stage where the scale of facilities can be accommodated on a regional basis, some of the ambitious plans that are emerging (e.g., for Electron Ion Colliders or next generation ISOL facilities) may need to be considered on a world basis. BRIAN FULTON NuPECC Chair 4 Nuclear Physics News, Vol. 18, No. 4, 2008 DENNIS KOVAR DOE Former Associate Director of Science for Nuclear Physics laboratory portrait The Nuclear Physics Laboratory at CEA DAM Ile-de-France Introduction The Nuclear Physics Laboratory (Service de Physique Nucléaire, SPN) belongs to the Military Application Division (Direction des Applications militaries, DAM) of the French Atomic Energy Commission (Commissariat à l’Energie Atomique, CEA). It is located in the DIF (DAM Ile de France) research center in Bruyères-le-Châtel, 30km south of Paris. The laboratory houses 44 staff members, plus several PhD students, post docs, and foreign visitors. Its programs range from support to the DAM Simulation program, to fundamental experimental and theoretical nuclear physics studies. The originality of SPN actually resides in that continuous coverage of the whole spectrum of nuclear physics from fundamental studies to applied physics. Since its creation, almost 50 years ago, most of the scientific activities, especially the experimental ones, involve the neutron; either as an incoming or an outgoing particle, and many (n,γ), (n,n’), (n,xn), or (n,f) cross-sections have been measured in Bruyèresle-Châtel. Theoretical studies were also initiated long ago in the domains of nucleon–nucleus reactions and microscopic nuclear structure theory. Today, the programs carried out in SPN can be roughly grouped into four main research directions: • • Theoretical studies of the nuclear many-body problem with applications to both nuclear structure and nuclear reactions. Experimental and theoretical studies of the fission phenomenon. • • Studies on short-lived nuclear states or isomers, including their interactions with laser-induced plasmas. Nuclear data for applications and their covariances. Naturally, these four topics exhibit some overlap. For example, fission studies have a strong impact on nuclear data works, or the many-body calculations of nuclear structure produce results that are further used in fission, isomer, or nuclear data studies. Actually, that overlap between topics is a clear manifestation of the complementarities and strong interactions between the SPN physicists. Nevertheless, those internal complementarities do not preclude collaborations, as evidenced by our strong involvement in many national and international collaborative efforts. Before going into each of the four main topics, the present article shall first detail our on-site experimental facilities as well as our current array of detection systems. Facilities Besides the aforementioned four main research topics, SPN also operates a KN4000 4 MV Van de Graaff electrostatic accelerator facility for applications like measurement of neutron cross-sections, neutron or gamma detector calibrations, and chemical analysis of matter using ion beams. That facility is used in support of many of the experimental studies pursued at SPN. The 4 MV Van de Graaff is an HVEE-electrostatic accelerator that delivers 1H+, 2H+, 3He+, and 4He+ ions within the energy range 420 keV to 4 MeV. Possible Xe+ ions beam was added in the eighties on a specific beam-line. Pulsed or continuous ion beams are available. In pulsed mode, the repetition rate is fixed at 2.5 MHz (400 ns) and the FWHM is about 10 ns. Attached to that accelerator are five beam-lines serving the two experimental rooms. One of these beam-lines is dedicated to the neutron production with a Mobley buncher (to reduce the FWHM of the pulsed beam to 1–2 ns), a capacitive beam pick-off detector (to measure that FWHM) and two NE213 and BF3 detectors, to monitor the neutron flux on-line. Mono-energetic neutrons are created by nuclear reactions between the accelerated 1H+, 2H+ ions, with thin layer of lithium, or deuterium, or tritium-loaded Ti. Neutron energy is defined by the specific reactions and by choosing the appropriate angle. The range of energy is 30 keV to 20 MeV and the neutron emission rate is of the order of 107 n/s/sr. That accelerator is shared in the EFNUDAT [1], 6th Framework European program for encouraging transnational access to nuclear physics infrastructure among member countries. SPN is also strongly involved in the project of the future NFS (Neutron For Science) neutron source that should be constructed as a part of the SPIRAL2 facility in GANIL (Caen, France) in the year 2012. That NFS neutron source will deliver neutrons in a continuous spectrum peaking near 20 MeV with intensities much stronger than that of the other European facilities (Gelina, nTOF) in that energy range. Finally, for theoretical studies, computing facilities constitute the Vol. 18, No. 4, 2008, Nuclear Physics News 5 laboratory portrait Q1 Figure 1. The 4 MV Van de Graaff electrostatic accelerator of SPN (open with the visible glowing ion source). counterpart to experimental facilities. CEA DAM Ile-de-France hosts two high-performance computing centers, CCRT and TERA, which allow us to develop ambitious theoretical programs that require large amounts of computing power. Detection Systems SPN currently operates three major detector systems. The CARMEN detector (Cells Arrangement Relative to the Measurement of Neutrons) [2] is a large organic scintillator tank-type detector devoted to neutron counting. It is the continuation of a long SPN tradition since the first neutron counting ball was built in 1964 by M. Soleilhac. CARMEN consists of two independent vertical hemispheres, each one equipped with 12 photomultipliers. The active part which is a gadolinium-loaded scintillating organic liquid (BC521) has a total volume of 1m3. Like in many detectors of this type, neutrons are moderated in the organic liquid before being captured 6 mainly by the Gd nuclei. In the case of CARMEN, the neutron detection is spread over the 50μs following the nuclear reaction (99% of the neutrons are captured at that time). This time spreading allows for counting neutrons even for high-multiplicity events. Hence this detector is adequate for (n,xn) measurements. CARMEN is a highefficiency detector (85% efficiency for 252 Cf fission neutrons). Moreover, the distance between the two hemispheres can be adjusted according to the experiment’s needs. This peculiarity allows measurements of neutron spectra correlated to neutron multiplicity. Since the beginning of 2008, we have been developing a 3He based neutron counter. It consists of a 50*50*75cm3 polyethylene block with 23 inserted 10 bars 3He proportional counters. This device works similarly to CARMEN: neutrons are first moderated in polyethylene before reacting with the 3 He counters. It is nevertheless completely insensible to gamma rays. It also possesses an external shielding (10cm Nuclear Physics News, Vol. 18, No. 4, 2008 of polyethylene and 4mm of inner boron carbide). Its detection efficiency is 50% from fission neutron from 252Cf. Although this detector is mainly a counter, it is able to provide a rough estimate of neutron spectra. Such an instrument can be used for fission studies and (n,xn) reaction measurements. The Lead Slowing Down Spectrometer (LSDS) installed on the WNR neutron source at the Los Alamos National Laboratory (USA) was first operated in Bruyères-le-Châtel as the CIRENE assembly. At that time, it was devoted to isomeric ratio measurements in the resonance region. Its installation at the WNR intense source gives the opportunity to measure cross-sections on very small matter quantities (down to 10ng), or to measure very small cross-sections for neutron energies ranging from 0.1eV to 100keV. That method was first demonstrated in 1955 [3]. It profits from the great probability for neutrons to scatter elastically in natural lead, and from the very strong time/energy correlation within the cube. The gradual slowing of neutrons in the cube produces a gain in apparent neutron flux of the order of 103 compared to usual time of flight bases. In this way the useful neutron flux on the LSDS at Los Alamos can be as high as 4.1010 n/cm2/s. Theoretical Nuclear Many-Body Problem The theoretical treatment of nuclear structure with mean-fieldbased approaches has long been a specificity of our laboratory. The heritage of pioneering works of Daniel Gogny on the effective nuclear interaction [4] and its use within the frameworks of mean-field [5] and beyond-the-mean-field theories is still living. Those theories constitute a base on which are built modern fundamental developments. These theories laboratory portrait exhibit a strong predictive power that can be challenged by experimental data like mass or nuclear spectroscopy of stable and unstable nuclei. The current thrust in those studies consists in using the Gogny interaction in approaches that include more and more correlations beyond the single-particle picture of the mean field approximation. Such approaches are for example QuasiParticle Random Phase Approximation (QRPA) [6], multi-particle multi-hole configuration mixing [7], or Generator Coordinate Method (GCM) [8]. The nuclear properties predicted within these theoretical frameworks are then compared with the latest experimental data on unstable nuclei, allowing us to contribute to the fundamental understanding of nuclear stability, the persistence or erosion of (sub-)shell gaps far from the beta stability line, giant resonances, and nuclear shape coexistence [9]. Another theme of study consists in large-scale systematic calculations of nuclear properties, which provide a wealth of results that can be exploited to get a better picture of the global evolution of nuclear properties across the chart of nuclei [10]. These studies are made possible by the availability of massive amounts of computing power at the CCRT and TERA computing centers. Our website (http://wwwphynu.cea.fr) presents extensive calculations of the stable and unstable nuclei as they are predicted, from drip-line to drip-line, within axially symmetric Hartree-Fock-Bogoliubov (HFB) framework using the Gogny D1S interaction. The D1S interaction itself is presently under review, and several improvements to that interaction are currently investigated [11]. Another trend in the nuclear manybody problem is the convergence of structure and reaction studies. A first example of such a convergence is the use of approaches based on HFB and collective dynamics for fission studies. Another example resides in the growing use of ingredients derived from theoretical nuclear structure studies in reaction models, such as level densities derived from single particle levels or nuclear matter radial densities in finite nuclei. These will be discussed in the section on “nuclear reaction modeling.” Fission SPN has been involved in the study of fission for many years. The works by Fréhaut and collaborators about 30 years ago on fission neutron multiplicity measurements from the resonance region up to 28 MeV are still a basic reference [12]. In the field of theory, the pioneering work of Berger et al. was the first to achieve a microscopic description of the scission of fissioning systems, as well as the transition from fission to the fusion valley [13]. Today, nuclear fission is one of the main research fields in SPN. The approach is triple: experiments, theory and nuclear data evaluation. Experimental Fission Studies A program for measuring fission neutron energy spectrum and multiplicity in neutron-induced fission in the 1–200 MeV range has been initiated at the Los Alamos Neutron Science Center (LANSCE). This work provides unprecedented data for 238U, 235U, and 237Np [14], the interpretation of which is performed in conjunction with the theorists. More complex experiments including fission fragment mass measurements are foreseen. Fission is also studied on the spallation-driven LSDS. The group is also at the origin of a novel experimental project to be performed at the ELISE Electron–ion collider to be constructed at FAIR the future facility at GSI, Darmstadt. The goal of this reverse kinematics experiment is to measure event by event the main fission observables with an unprecedented precision: unambiguous Q1 Figure 2. The Lead Slowing Down Spectrometer installed at the WNR neutron source in Los Alamos National Laboratory. Vol. 18, No. 4, 2008, Nuclear Physics News 7 laboratory portrait separation in mass and charge of both fragments, fragment kinetic energy, fission neutron multiplicity, and energies for tens of actinides and subactinides. The detectors required for the project are currently being designed. This experiment is expected to be a real breakthrough in the experimental study of nuclear fission and to enrich very significantly both quantitatively and qualitatively our knowledge on the fission mechanism and at the same time the data bases required for applications. In a more applied field, a program in collaboration with the CEA/IRFU in Saclay for characterizing the delayed neutron emission in gamma-induced fission is carried on for a selection of actinides. The purpose is to provide data for libraries and evaluations in the framework of applications for nuclear material detection in freight transportation [15]. In the future, the structure of fission fragments will be extensively studied at projected facilities such as SPIRAL2, which is scheduled to produce its first radioactive beam in 2015 in GANIL, or at the projected EURISOL facility. That availability of fission fragment beams will eventually produce strong experimental constraints for theoretical nuclear structure, as well as key ingredients for fission studies relative to the prompt and delayed decay of fission fragments. Theoretical Fission Studies The theoretical counterpart to the fission measurements described earlier consists in attempting to understand and describe the observables associated with the fission process using microscopic theoretical physics approaches. Approaches built on the established many-body treatment of nuclear structure (see the earlier section “Theoretical Nuclear Many-Body Problem”) are developed today. In the mean-field framework, the potential energy of the fissioning nucleus can be calculated as a function of collective coordinates (like elongation, asymmetry, etc.). This potential energy surface can then be used to specify a scission line and fission frag- Q1 Figure 3. Mean energy of prompt fission neutron for the 238U(n,f) reaction measured at LANSCE (symbols) as a function of the incident neutron energy compared with model calculations (curve). 8 Nuclear Physics News, Vol. 18, No. 4, 2008 ments properties at each point of that scission line [16]. That potential energy surface can also be further used as a potential for the dynamical solving [17] of the time-dependent Schrödinger equation for the collective wave function of the fissioning nucleus. By calculating the flux of that wave function transmitted through the scission line, fission fragment yields can be predicted using only the Gogny effective interaction as input. The theoretical fission fragment yields calculated in this manner are qualitatively close to experimental values. Finally, the prompt neutron and gamma emission can be predicted by allowing the fission fragments (of which the yields and characteristics are calculated above) to decay according to the statistical model. Again, the observables calculated in this way are qualitatively comparable to experimental data. That qualitative agreement shows that the leading order effects are all included properly in the calculations. Besides the obvious thematic overlap with nuclear data for applications, fission is also a formidable laboratory to challenge our understanding of fundamental nuclear structure. For example, fission modeling involves large amplitude collective motion of the nucleus, dynamic coupling between several collective modes, as well as between collective and individual (particle-hole) degrees of freedom. The theoretical and experimental studies of fission are thus strongly linked to the more fundamental understanding of the static and dynamic structure of nuclei far from equilibrium configurations. Nuclear Physics in Plasmas, Nuclear Physics with Lasers, and Nuclear Isomers The isomeric states play an important role in nuclear physics. Nuclear isomers are very good probes to study laboratory portrait nuclear structure, because of their usually pure or quasi-pure single particle configurations. The experimental information collected in those studies is of course compared to the predictions of nuclear structure theoretical models, and contributes to their experimental validation. Moreover, the understanding of the formation and de-excitation of nuclear isomers is a scientific challenge. Our laboratory is involved in various fields, centered on the isomers’ properties: nuclear moment measurement, interaction processes between isomer and neutron, and isomer excitation in plasmas. Nuclear Moments of Isomeric Nuclei Measurement of electromagnetic moments is of wide interest in subatomic physics. In nuclear physics, within the extremely simplified singleparticle model, magnetic moments of odd mass nuclei are directly linked to the orbital occupied by the unpaired nucleon. Measuring such moments thus allows one to unambiguously probe nuclear structure and its evolution throughout the nuclear chart. The electric quadrupole moment is more sensitive to the collective nature of the state, and is a good observable to quantify nuclear deformation. Our laboratory is specialized in measuring both magnetic and electric quadrupole moments of isomeric states, and is part of the “g-rising” collaboration. To perform such experiments, one should first produce nuclei in isomeric states of interest with sufficient spin alignment. To do so, several kinds of nuclear reaction are at our disposal: fragmentation reactions (GANIL, GSI, MSU), fission fragments (GSI, ILL), and (d,p) particle transfer reactions in direct kinematics (Orsay, Bruyères-le-Châtel) in order to prepare reverse kinematics experiments at the future SPIRAL2 radioactive beam facility. These experiments rely on the Time Dependent Perturbed Angular Distribution (TDPAD) method in combination with heavy ion-γ correlations. This method takes advantage of the perturbation of the aligned spin of the isomeric state induced using external magnetic or electric fields. Several magnetic and quadrupole electric moments have been measured in the region of neutron rich nuclei mainly located around the N = 28 and N = 4 0 (sub)-shell closures. Neutron–Isomer Interaction Nuclear isomers are promising candidates to store and release energy on request. However, the induced deexcitation of isomers comes up against an antagonism: the higher the isomer half life the more difficult de-excitation is. The induced de-excitation of K isomers may be different because the half-life of K-isomers is not only due to the spin difference but also to the K difference (K is the projection of the total nuclear spin on the symmetry axis in deformed nuclei). At low excitation energy, K can be approximated to be a good quantum number and the nuclear transitions depend on K conservation. At neutron separation energy, a complete disappearance of K quantum number is expected. Hindered transition between two states with a large K difference could thus be circumvented via the formation of a compound nucleus. The 160-day 23/2− isomer in 177Lu located at 970 keV is a candidate for observing an induced de-excitation by neutron scattering. During a collision between a neutron and an isomer, the nucleus can partly transfer its excitation energy to the scattered neutron leading to the de-excitation of the isomer. This process is called neutron super-elastic scattering. To address this process study, collaboration between CEA laboratories produced a 177 mLu target at the Institut Laüe Langevin in Grenoble by thermal neutron irradiation of a highly enriched (99.993%) 176Lu powder. Following the irradiation period, the sample was cooled down to remove the 177Lu ground state, which is short lived (6.647 ± 0.004 days) compared to the isomeric state (160.44 ± 0.06 days). Finally, nanograms of Lutetium, 1014 atoms, were extracted by chemical separation before producing the isomeric targets by a direct deposit method on backings. To measure the super-elastic crosssection at neutron thermal energy, we used an original method involving two types of measurements: the isomer radiative capture cross-section and the isomer burn-up cross section. The super-elastic cross-section, 258 ± 58 b, was obtained by subtracting the radiative capture cross-section from the burn-up cross-section. This is the highest value ever measured for this process. The ratio between the superelastic and radiative cross-sections is close to 0.6, showing the importance of the neutron-induced de-excitation channel. This encouraged us to pursue investigations by directly measuring the super-elastic process. That program is in progress at the Orphée reactor in Saclay. Nuclear Excitation in Plasma The last decade witnessed a fast development of power lasers that now allow studying matter in extreme density and temperature conditions. With these lasers, it has become possible to create plasmas at high enough temperatures to induce high fluxes of Vol. 18, No. 4, 2008, Nuclear Physics News 9 laboratory portrait de-excitation may occur with significantly different lifetimes. Q1 Figure 4. Potential energy surface of the 238U fissioning nucleus calculated as a function of the quadrupole and octupole collective coordinates, within the HFB framework using the D1S effective interaction. energetic particles in a highly ionized medium. Under these conditions, the atomic nucleus is not left unperturbed. On the one hand, the plasma particles can induce nuclear reactions, and on the other hand, the modification in the electronic environment of the atom greatly modifies interaction processes between the nucleus and the atom, such as nuclear lifetime and reaction rates. For heavy nuclei, the nuclear lifetime of discrete levels is often strongly dependent on internal conversion, which involves bound electrons. In plasma, many of these electrons are no longer in a bound state and the internal conversion rate can be significantly reduced. Its coupling with its inverse process (Bound Internal Conversion), Nuclear Excitation by Electronic Capture (NEEC), can lead to greatly increased nuclear lifetimes. In some cases, an atomic transition can be coupled with a nuclear transition in a process called Nuclear Excitation by Electronic Transition (NEET) if 10 their transition energies are closely matched. This can accelerate the deexcitation of the excited nuclear level, and reduced its lifetime. We developed a model able to deal with these processes in plasma under thermodynamic equilibrium. It evaluates internal conversion, NEEC, and NEET rates in plasma. Depending on the particular situation, we used an average atom description or a Multi Configuration Dirack Fock (MCDF) approach to describe the electronic environment of the atom. Large variations of several excited nuclear-level lifetimes have been predicted. For example, the first excited state of 201 Hg, an excited level lying 1.565 keV above ground state, has a de-excitation lifetime that increases from 81 ns under laboratory conditions up to 1 ms when the plasma temperatures reaches around 1 keV (Figure 5). A complete description of the nuclear lifetime must also include some other nuclear levels through which indirect nuclear excitation or Nuclear Physics News, Vol. 18, No. 4, 2008 Nuclear Data The fundamental knowledge of nuclear physics is not directly usable for applications such as energy production using thermal or fast spectrum fission reactor (GEN IV project), fusion studies (ITER), shielding, medical, geological, and space applications. For that purpose, the available experimental and theoretical information must be synthesized into the so-called evaluated nuclear data files. Across the world, several approaches of that synthesis process (called evaluation) are put into practice. SPN has chosen to focus on an approach that uses the results of nuclear reaction models, whose parameters are constrained by experimental data. This approach implies dedicated work on nuclear reaction models on the one hand, and nuclear reaction experimental data on the other hand. Nuclear Reaction Modeling Because nuclear reaction models are at the heart of our nuclear data evaluation process, they constitute an important focus of our laboratory. In the continuum region (above the resonance region), the relevant nuclear models are the optical model for direct reactions, pre-equilibrium models, and the statistical Hauser-Feshbach decay of the compound nucleus. Depending on the availability of enough experimental data to constrain the model parameters, two options are open for the modeling of nucleoninduced direct reactions. When experimental constraints are available, the dispersive phenomenological optical model potential [18] allows very precise restitution of experimental scattering measurements. Conversely, if laboratory portrait experimental data is unavailable, direct reactions observables can be predicted with the semi-microscopic optical model potential [19], built using nuclear radial densities obtained from HFB theoretical nuclear structure calculations. In between these two lies the global phenomenological optical model potential [20], which is widely used due to its ease of use as well as its globally good quality. For deuteron-induced direct reactions, the CDCC (Continuum Discretized Coupled Channels) approach [21] has been developed to explicitly take into account the break-up of the weakly bound deuteron. An essential ingredient of the modeling of the statistical compound nucleus decay is the level density of each possible final state of the compound nucleus. To go beyond the adjusted level density formulae based on the Fermi gas model, a combinatorial approach [22] that uses single-particle levels from HFB structure calculations has been developed. The aforementioned ingredients are combined in the TALYS [23] nuclear reaction code, which is developed in collaboration with NRG Petten (Netherlands). TALYS includes many state-of-the-art nuclear reaction models to cover all the main reaction mechanisms encountered in light particleinduced reactions up to 200 A MeV. It can provide a complete description of all the open reaction channels with only a minimal input (4 lines), but can also be operated in expert mode using many (over 250) keywords that specify options and parameters for the nuclear model calculations. The modeling of high-energy reactions is also of interest for applications like Accelerator Driven Systems, shielding, or assessment of effect of high-energy particle on electronics in aerospace applications. Such calculations can be performed using the BRIC-BRIEFF [24] intra-nuclear cascade code. That code has recently been extended toward incident nucleon energies as low as 14 MeV, which overlap with the energy region where the TALYS code is relevant, allowing for inter-comparisons between codes. Experimental Nuclear Data Measurements Experimental nuclear data is essential to constrain as well as validate the nuclear reaction models described earlier. Besides the fission experimental works, which are already covered in the section on experimental fission studies, the (n,xn) reaction is the prominent non-elastic process for fast neutrons incident on non-fissionable nuclei. For example, in the 7–20 MeV energy range the (n,2n) reaction is one of the most important nuclear-reaction channels. Simulation codes involve several models (optical model, direct interaction, pre-equilibrium, and evaporation) to reproduce the whole reaction process. Among these processes, the pre-equilibrium is clearly the least well known. Although some of the existing models are able to reproduce integrated observables, differential measurements are more challenging. In order to provide experimental information relevant to the preequilibrium process, we have performed an original measurement of the energy spectra of neutrons in (n,xn) reactions in coincidence with neutron multiplicity. Contrary to “classical” (n,xn) reaction measurements where all the channels emitting at least one neutron are taken into account, the double differential cross-section in (n,2n) tagged reactions are extracted. The CARMEN detector was specially designed for such studies and was used in coincidence with NE213 neutron detectors. These measurements were performed between 8.3 and 13.3 MeV on Bi and Ta targets [2]. The neutron–deuteron interaction is also under experimental investigation in parallel to theoretical studies. A rigorous calculation of the neutroninduced deuteron break-up cross-section was carried out for neutron energies up to 30 MeV. The quality and consistency of the existing experimental and evaluated data lead us to believe that the evaluated cross-section of the neutron-induced deuteron break-up exhibits uncertainties of the order of 20–30%. New and more accurate experimental data are thus necessary to cover the 5–10 MeV and 15–30 MeV energy ranges. Such measurements were performed on the low background and collimated beam-line of the Tandem 7 MV accelerator (now decommissioned) in Bruyères-le-Châtel. A scintillation detector C6D6 is used as deuteron target and is set up within the reaction chamber of the CARMEN detector that allows one to count the number of outgoing neutrons emitted Figure 5. Nuclear lifetime of the isomeric level of 201Hg. Vol. 18, No. 4, 2008, Nuclear Physics News 11 laboratory portrait in a D(n,2n) reaction. A NE213 detector is placed in the beam to monitor the neutron flux, and ensures the normalization of the measured D(n,2n) cross-section. Evaluation Activities The last step in the evaluation process consists in using nuclear reactions codes to produce evaluated data files that are consistent with the available experimental information, thus synthesizing the theoretical and experimental knowledge of the day. For present day nuclear energy applications, the most important reactions are of course the neutron-induced reactions on the major actinides 235,238U and 239Pu. These involve adjusting the many parameters associated with the phenomenological modeling of the fission process [25] using constraints coming from both nuclear physics experiments and critical assembly integral experiments. We collaborate with CEA DEN Cadarache on both the validation of nuclear data files and their extension toward the resonance region. Once a nuclear data file is complete and validated it is submitted to the JEFF (Join European Fusion Fission) project, to be further tested and eventually included in the JEFF nuclear data library (NDL). The JEFF NDL is a reference library of evaluated and validated nuclear data, recommended for use in fusion and fission applications. In the most recent JEFF 3.1 neutronic library released in 2006, out of 381 isotopes, SPN has contributed to 8 (n + 103Rh, 127,129I, 236,237,238U and 239,240Pu). For the coming JEFF 3.2 library, more isotopes are prepared in collaboration with CEA DEN Cadarache and NRG Petten. In parallel, a significant effort has been devoted to the new JEFF3.1.1 12 Decay Data and Fission Yields sub-library. The next frontier in the field of evaluated data consists not only in providing the best possible nuclear data based on the synthesis of the available experimental and theoretical knowledge, but also in estimating the uncertainties associated with these evaluated data. These uncertainties are used to assess the operating margins of future nuclear energy projects like the GEN IV nuclear reactors. The rigorous estimation [26] of these uncertainties needs to take into account both the dispersion and error bars of experimental data, as well as the uncertainties associated with the models and their parameters. A large international effort is underway to produce uncertainty information for the new files in the future JEFF 3.2 release. Conclusions The Service de Physique Nucléaire of the CEA DAM Ile-de-France contributes equally to the advancement of knowledge in fundamental and applied nuclear physics. SPN is deeply involved in many collaborations, both present and future, within CEA, in France, in Europe, and internationally. The theoretical and experimental studies performed in SPN contribute to the excellence of French institutional research at large, and to the scientific credibility of the CEA DAM programs in particular. References 1. http://www.efnudat.eu 2. I. Lantuéjoul, PhD Thesis, University of Caen (2004). 3. A.A. Bergman and al. Proceedings of the First International Conference on Nuclear Physics News, Vol. 18, No. 4, 2008 Peaceful Uses of Atomic Energy, Geneva, vol 4, 1995, p 135. 4. J.F. Berger, M. Girod, D. Gogny, Comput. Phys. Comm. 63, 365 (1991). 5. J. Dechargé, D. Gogny, Phys. Rev. C 21, 1568 (1980). 6. S. Peru, H. Goutte, Phys. Rev. C 77, 044313 (2008). 7. N. Pillet, J.F. Berger, E. Caurier, Phys. Rev. C 78, 024305 (2008). 8. E. Clement et al., Phys. Rev. C 75, 054313 (2007). 9. J.P. Delaroche et al, Nucl. Phys. A 771, 103 (2006). 10. G.F. Bertsch et al. Phys. Rev. Lett. 99, 032502 (2007). 11. F. Chappert, M. Girod, S. Hilaire, Phys. Lett. B 668 420 (2008). 12. Fréhaut et al., EXFOR reference W, Frehaut, 8009. 13. J.F. Berger et al., Nucl. Phys. A428 23c (1984). 14. T. Ethvignot et al., Phys. Lett. B575,221 (2003); T. Ethvignot et al., PRL 94, 052701 (2005); J. Taieb et al., Proceedings of the Nuclear Data Conference, Nice 2007. 15. D. Doré et al., Proceedings of the Nuclear Data Conference, Nice 2007. 16. N. Dubray, H; Goutte, J.P. Delaroche, Phys. Rev. C 77, 014310 (2008). 17. H. Goutte et al., Phys. Rev. C 71, 024316 (2008). 18. B. Morillon, P. Romain, Phys. Rev. C 70, 014601 (2004). 19. E. Bauge, J. P. Delaroche, M. Girod, Phys Rev. C 63, 024607 (2001). 20. A.J. Koning, J. P. Delaroche, Nucl. Phys. A 713, 231 (2003). 21. Huu-Tai P. Chau, Nucl. Phys A 773, 56 (2006). 22. S. Hilaire, S. Goriely, Nucl. Phys. A 779, 63 (2006). 23. http://www.talys.eu 24. H. Duarte, Phys. Rev. C75, 024611 (2007). 25. M.J. Lopez-Jimenez, B. Morillon, P. Romain, Ann. Nucl. Energy 32, 195 (2005). 26. M.B. Chadwick et al., Nucl. Data Sheets 108, 2742 (2007). ERIC BAUGE Bruyères-le-Châtel feature article Deep Underground Laboratories—Somewhere Quiet in the Universe NEIL SPOONER University of Sheffield, ILIAS, LAGUNA, and Boulby Laboratory Introduction: Nobel and Noble Dreams The world’s very deep underground laboratories offer access to the ultimate in quiet environments for science research. Here the term quiet generally refers to the cosmicray muon flux that is greatly reduced in these laboratories compared to that at the surface. It is this feature that allows observation or searches for very rare fundamental physics processes, impossible to undertake on the surface because of the muon-induced background. Perhaps most notable of these is solar neutrino physics, for which, after a long history, Ray Davies received in 2002 with Masatoshi Koshiba the Nobel prize for measurement of neutrinos from the Sun. Such work falls firmly within the field of Particle Astrophysics—the use of particle physics to study astrophysics and of astrophysics to study particles. However, in the underground world quiet increasingly means also low vibration noise, low electrical noise, low natural radiation, low radon gas, and even low biological contamination. Realization of this, and that for particle physics the next big energy frontiers may in fact more economically be reached via new opportunities underground than at accelerators, is starting to generate a revolution of development. Large new experiments are planned, many laboratories are pushing expansion schemes, and new deep laboratories are being built. The discipline once termed Underground Particle Astrophysics and devoted mainly to solar neutrinos is transforming into a diverse field, itself becoming a sub-topic of a new interdisciplinary field called simply Underground Science. This renaissance is perhaps best exemplified by the enthusiasm for construction in the United States of a hugely ambitious new national laboratory, the Deep Underground Science and Engineering Laboratory (DUSEL) [1]. After an intense competition over several years the location of the £0.5B DUSEL was chosen in April 2007 to be the disused Homestake Gold Mine in South Dakota. The laboratory has already attracted interest as a site for around 100 experiments, split between particle astrophysics and a range of new science that includes significant microbiology interests. Q1 Notable among the latter is work on so-called Dark Life, the search to understand the origins of the microbial life found in abundance in deep rock. Around 50% of the world’s total biomass is underground. Dark Life aside, DUSEL, if given the final go-ahead by the U.S. Congress, is hugely exciting for nuclear and particle astrophysics, providing opportunities for the United States to contribute better to the growing range of large, next generation experiments being developed at European sites and in Asia. Among these is a growing enthusiasm for the use of liquid noble gas technology, argon, neon, and xenon, as possibly the next great detector technology (see Figure 1). The World’s Deep Laboratories—Deep and Dirty To put this in context, shown in Table 1 is a compendium comparing vital characteristics of the world’s current and up-coming most well-known deep underground sites and in Table 2 an overview of the experimental activity and status of expansion plans, where known (see also Ref. [2] and related sources). The first characteristic generally of interest to users is the depth (Table 1, column 4) because this is related to the level of cosmic-ray shielding provided by the rock. Traditionally, this is given in m.w.e. (meters water equivalent), the depth normalized to the density of water (to allow for different rock types). However, great caution is needed with m.w.e. because this may refer just to the vertical depth above the laboratory which, for a mine site in particular, tends to underestimate the relative shielding, because most lines of sight from the laboratory to the surface pass through a greater thickness of rock than that of the vertical depth. A better comparison for most purposes, which naturally accounts for the averaging of the rock cover, is to use the actual measured muon flux (also in column 4). This also accounts for the slight effect of different latitudes and altitudes. It should be noted here that there are a much larger number of underground laboratories at shallower depth not shown here, for instance as covered in Europe by the organization CELLAR [3]. These sites, in general less than 200-m deep, undertake, for instance, low Vol. 18, No. 4, 2008, Nuclear Physics News 13 feature article Figure 1. The first ton-scale dark matter detector, ArDM, uses liquid argon—seen here undergoing tests at CERN [2]. background measurements of materials but are not involved in front-line fundamental research. Perhaps unique to the deep laboratories (see Table 1), is the significant range of characteristics that reflect not just the requirements of the science but the severe constraints imposed by geographic and local economic factors required for establishing a deep underground site. This arises because underground science alone has not so far provided sufficient justification to fund the necessary access excavation. Rather, almost all sites piggyback off an existing underground infrastructure, usually a public road tunnel or deep mine. This situation introduces other peculiarities and challenges for the 14 laboratories. In particular, the need to cooperate closely with the host owners, the public road authorities, mine company, national park, or other bodies that all impose constraints. These economic and ownership factors have partly limited both the number of sites and their scope for expansion, resulting in a significant lack of deep space for science, particular at greater depths. Recognizing this, there has been a trend in recent years toward better coordination between laboratories, to exchange best practice and experience to improve efficiency for the user, but also toward coordinated, more efficient, allocation of space. The aim being to site experiments at the laboratories best suited to their scientific needs rather than for geographical reasons. A particular case is dark matter experiments searching for Weakly Interacting Massive Particles. As the need to probe to everlower cross-sections increases, so does the need for greater depth, to reduce further the muon-induced neutron background. Some priority will be needed to move next generation dark matter experiments to sites with the necessary depth, while other classes of experiment proposed, for instance for proton decay using liquid argon like GLACIER, can function comfortably at shallower sites [5]. Coordination between laboratories is exemplified in Europe by the highly successful new organization ILIAS (Integrated Large Infrastructures for Astroparticle Science) [6]. Set up in 2003 and funded by the European Union, ILIAS has brought together the four main deep laboratories in Europe—Boulby, Canfranc, Frejus, and Gran Sasso. ILIAS involves over 20 institutes representing around 1,500 scientists with interest in underground physics and gravitational waves. ILIAS is run through a set of six networks, three joint research projects, and a Trans-national Access Programme (TA). Particular success has been production of the first databases collecting together information on low background materials and techniques produced by the laboratories [6]. A specific laboratory network has produced joint safety training and policy activity and, through regular meetings between the directors, progress toward coordinating science policy. The TA underpins much of ILIAS, providing a jointly run fund to which groups can apply for resources to gain access to any of the laboratories. Important Comparative Features—Rock and a Hard Place Comparing again the characteristics of the laboratories (Table 1), several particular features and their interaction with the science are worth noting. Nuclear Physics News, Vol. 18, No. 4, 2008 feature article Table 1. Summary characteristics of the world’s deep underground laboratories. Site Location and access Current space Depth and muon flux (m m-2 s-1) Rock and radon (Bq m-3) 850 m.w.e. and 4,700 m.w.e. (SAGE area); 3.03 ± 0.19 × 10−5 40 norite rock 1.4 × 10−3 (>1 MeV); 6.28 × 10−4 (>3 MeV) Neutrons (m-2 s-1) Europe BNO Andyrchi, Russia; 3 halls: 24 × 24 × 16 m3; independent tunnel 60 × 10 × 12 m3; 40,000 m3 BUL Boulby mine, UK; vertical 1,500 m2 2,800 m.w.e. under flat surface; 4.5 ± 0.1 × 10−4 1–5 salt 1.7 × 10−2 (>0.5 MeV) CUPP Pyhasalmi mine, Finland; vertical >1000 m2 spaces no longer used by the mine down to 1,400 m — pyrite ore, zinc ore — LNGS Gran Sasso, Italy; road tunnel 3 halls plus tunnels total 17,300 m2; 180,000 m3 3,200 m.w.e., under mountain; 3 × 10−4 50–120 CaCO3 and MgCO3 3.78 × 10−2 (total); 0.32 × 10−2 (>2.5 MeV) LSC Canfranc, Spain; road tunnel 2 halls: 40 × 15 × 12 m3; 15 × 10 × 8 m3; tot 1,000 m2 2,400 m.w.e., under mountain; 2 × 10−3–4 × 10−3 50–80 limestone, 2 × 10−2 LSM Modane, France; road tunnel 1 hall and service areas: 400 m2 4,800 m.w.e. under mountain; 4.7 × 10−5 15; (0.01 filtered) calcitic schists 5.6 × 10−2 (work in progress) SLANIC Prahova mine, Romania; vertical 70,000 m2 average ht. 52–57 m 208 m, under flat surface 6 salt — SUNLAB Sieroszowice mine, Poland; vertical 85 × 15 × 20 m3 900–950 m (2200 m.w.e.) 650–700 m for large caverns 20 salt and copper ore — SUL (Uk) Solotwina mine, Ukraine; vertical 25 × 18 × 8 m3; 4 of 6 × 6 × 3 m3; total area 1,000 m2 1,000 m.w.e. under flat surface; 1.7 × 10−2 33 salt <2.7 × 10−2 3500 m.w.e. — compacted granite — Asia INO (proposed) Masinagudi, India; 2 halls: 26 × 135 × 25 m3; 53 × 12 × 9 m3 independent tunnel Kamioka Japan; independent horizontal Hall SK 50 m dia; 40 × 4 and 100 × 4 m wuth L-arm 2700 m.w.e. 3 × 10−3 20–60 lead and zinc ore 8.25 ± 0.58 × 10−2 (th); 11.5 ± 1.2 × 10−2 (fast) Oto-cosmo Tentsuji, Japan; Indep. horizontal 2 halls: 50 m2; 33 m2; total ~100 m2 1400 m.w.e. 4 × 10−3 10 (radon reduced)— 4 × 10−2 Y2L YangYang, S. Korea; Current space: 100 m2 Planned space: 800 m2 horizontal ~2000 m.w.e. 2.7 × 10−3 40–150— 8 × 10−3 (1.5–6.0 MeV) North America DUSEL (proposed) Homestake, USA; vertical ~40–200 (at 1478 m) — 7,200, 4,500, 100 m2 at 1,450, 233, 4,100, 6,400, 7,000 2,200, 2,438 m dep m.w.e. under flat surface metasedimentary SNOLAB Creighton mine, Canada; vertical SNO ~200 m2; main 18 × 15 × 15–19.5 m3; ladders 6–7 m; total 46,648 m3 SUL (US) Soudan mine, USA;~ 2 halls: 72 × 14 × 14 m; 2,000 m.w.e under flat vertical 82 × 16 × 14 m; tot 2,300 m2 surface 2 × 10−3 WIPP Carlsbad, USA; vertical Kimballton Butt Mountain, USA; 30 × 11 × 6 m horizontal 500 × 8 × 6 m available 120; norite, granite gabbro 4.7 × 10−2 (th) 4.6 × 10−2 (fast) 300–700; Ely greenstone 2 × 10−2 (calc) 2,000 m.w.e. 2 × 10−3 expected <7; salt 115+/−22 m−2d−1 (th + ath) 1,400 m.w.e — Paleozoic dolomite — 6,001 m.w.e. under flat surface 3 × 10−6 Vol. 18, No. 4, 2008, Nuclear Physics News 15 feature article Table 2. Deep undeground experiments and plans. Site Users (approx.) Current experiments Future plans BNO Staff 50–60; Users 30–35 Neutrinos: BUST; SAGE Uncertain BUL Staff 2; Users 30 Dark Matter: ZEPLIN II, ZEPLIN III, DRIFT II; Other: SKY, ongoing R&D, HPGe measurements, geophysics Expansion to deeper hard rock underway; LAGUNA CUPP Staff 3–6; Users 10 Muons: EMMA Expansion study; LAGUNA LNGS Staff: 64 + 23 Users: 750 Dark matter: LIBRA, CRESST2, XENON10, WARP; Double Beta Decay: COBRA, CUORICINO, GERDA; Solar/geo/SN/beam neutrinos: BOREXINO, LVD, OPERA, ICARUS; Nuclear astrophysics: LUNA2; Other: VIP, LISA, R&D, HPGe, geology, biology, environmental studies MODULAr—New facility at shallow depth (1,200 m.w.e.) proposed LSC Being defined Being defined by open call. In old lab: ANAIS, Rosebud, R&D activity, 4 HPGe detectors LAGUNA LSM Staff 8–9; Users 100 Dark Matter: EDELWEISS; Double beta Decay: NEMO, BiPo, TGV; Other: SHIN, HPGe detectors ULISSE: 2 new halls: 100 × 24 m; 18 × 50 m (with water shield). MEMPHIS, LAGUNA SUL (Uk) Staff 14; Users 11+ Double Beta Decay: 116CdWO4 scintillators, SuperNEMO R&D; R&D on: CaWO4, ZnWO4, PbWO4, CaMoO4, new molybdates Uncertain SLANIC Variable MicroBq laboratory and whole body counting HPGe spectrometry; nuclear astrophysics; LAGUNA SUNLAB Being defined Being defined LAGUNA INO (proposed) Staff: 50–100 ICAL—50 kt magnetized Fe tracking calorimeter for atmospheric and very long base-line accelerator neutrinos Plans being prepared Kamioka Staff: 13 + 2 Users: >200 Neutrino astrohysics and beam: Super-Kamiokande, XMASS prototype, KAMLAND; Dark Matter: NEWAGE, XMASS; Gravity: CLIO; Double Beta Decay (proposed): CANDLE. New halls: 15 × 21 m for XMASS 800 kg; 6 × 11 m for CANDLE; gravitational antenna LCGT request; Hyper-K study Oto-cosmo Users: ~20 Double Beta Decay, Dark Matter: ELEGANTV, MOON-1, CaF2 uncertain Y2L Users: ~30 Dark Matter: KIMS; Double Beta Decay R&D; HPGe Can be expanded as desired DUSEL (proposed) Staff: >80 Users: >200 First experiments through SUSEL Inc. LUX (Dark Matter) Expansion depends on approval SNOLAB Staff: ~30 Users: >100 Neutrino astrophysics/Double Beta Decay: SNO+; Dark Matter: DEAP/CLEAN, PICASSO; Letters being considered SuperCDMS, EXO. Further site expansion limited by rock removal SUL (US) Staff: 9 Users: >200 Neutrino beam: MINOS; Dark Matter: CDMS II; low background Uncertain WIPP Staff: as needed Double Beta Decay R&D: EXO, MEGA/SEGA, MAJORANA Expansion to fill designated area Kimballton Staff: as needed Neutrino astrophysics: LENS, R&D Expansion to fill designated area Europe Asia North America 16 Nuclear Physics News, Vol. 18, No. 4, 2008 feature article The Rock The geology of a site is of course a critical factor. First, it determines the natural radiation background, both gamma, principally from the U, Th, and K levels in the rock, and the neutron background, from rock fission and muons [7]. These backgrounds are critical for most particle astrophysics experiments and require expensive passive or active shielding techniques, the design of which, principally the thickness and hence the cost, depend on this background. Extreme examples of note are sites in salt, such as WIPP, Boulby, and Slanic, for which the natural rock background can be exceptionally low. In harder granite-type rock, the background can be higher by 100 times or more. Although the background gamma flux is straightforward to measure, using a Ge detector for instance, it is much more challenging to determine the ambient fission and muon neutron background. New measurement techniques are being developed for this, for instance at Boulby and Modane [7,8]. Interestingly, these confirm simulations showing that although salt provides a gamma background significantly improved over other rock forms, the scattering process for neutrons in salt means the neutron background is not improved by nearly the same factor. The uranium content of the rock, together with the geology, porosity, and the ventilation characteristics, also critically determine the radon levels. Contamination by radon and its daughters is a major issue for many experiments with widely different concentrations encountered in the different sites. Again salt wins here with levels typically of a few Bqm−3, compared to 100–1,000 times more in some other sites (see Table 1). Nevertheless, all sites need to take precautions. At Modane for instance, a dedicated radon reduction plant has been pioneered that uses an array of cooled carbon filters [8]. Such plants will need to feature in new excavations seeking the lowest backgrounds. The rock type, in combination with the depth, seismic activity, faulting, water ingress, and other geology, obviously also determines the form of cavern that can be constructed, most notably the maximum safe height. Salt, for instance, undergoes plastic flow at depth, which restricts the excavations (without significant extra support) to heights perhaps <15 m, as at Boulby. Here, though, the length of excavation is essentially unlimited. However, at shallower depths, such as Slanic, this restriction relaxes. Here extraordinary caverns of 40–50 m in height have been in use for many decades (Figure 2). To create larger caverns at depth, harder rock, such as at Gran Sasso, is essential, although again depth is an issue as the rock pressure increases. The SNO cavity at Figure 2. The Slanic site in Romania—a relatively shallow site but with exceptionally large caverns excavated in salt. Creighton mine currently holds the record for the largest single cavity at depth. Tunnel versus Mine One striking difference between the sites for the user is the division between tunnel-based and mine-based sites. The advantages held by the former are often cited, for instance the benefits of horizontal access, such as at Modane and Gran Sasso. Meanwhile, a key disadvantage of a mine site is often stated to be the dependency on the mine owners, particularly the implications of cessation of mining. However, while horizontal access may be an advantage during experiment construction, allowing large single loads to be delivered by lorry, for the individual user vertical, walk-in, lift access, direct from a nearby surface facility, can be more convenient. Meanwhile, mine companies, such as INCO at SNOLAB or CPL at Boulby, are anyway well used to transport large items down shafts and fabricating underground—a process that can also allow better control of cleanliness for an experiment. Although it is clear that good relations are needed with mine owners for those sites, it is also the case that road tunnel sites are at the mercy of the relevant tunnel authorities. One concern is safety. This is a key matter in both cases but particularly for tunnel authorities because of the presence nearby of the general public, an increasing issue for tunnels highlighted in the Alpine sites by several recent fires. The advantage at a mine is that access for all personal is strictly controlled, there is no presence of mass general public nearby to consider, specific safety and evacuation training Vol. 18, No. 4, 2008, Nuclear Physics News 17 feature article Figure 3. Inside the Borexino detector at Gran Sasso. can be made compulsory for all, changed and improved as needed and the location of everyone can be monitored and controlled. Any incident can therefore be contained more quickly and is likely to have fewer repercussions. This degree of available control makes mine sites possibly also more suitable for future experiments requiring unusual or potentially dangerous materials, such as, for instance, large volumes of cryogenic gases or low flashpoint scintillators. The flexibility of mine sites through direct access on-site to excavation machinery and mining engineers, is a further advantage here. It allows existing caverns to be adapted or new ones built quickly if necessary, whereas for tunnels, once the road or dam building has been completed, major changes are problematic except in special circumstance. This ready prospect for new excavation also opens advantages for interdisciplinary science, notably access to fresh, uncontaminated rock. This is key for potential microbiology applications and in geophysics and engineering projects, such as waste management studies. Finally, no existing tunnel site can provide access to the great depth needed by many upcoming physics experiments, at least not without excavating a vertical shaft! Geographic Location A final point worth highlighting here are issues arising from geographic location. Through the dependency on a deep mine or mountain range to provide the over-burden, all current deep laboratories are located in relatively remote, rural areas. This introduces extra challenges for the user, notably from the limited transportation options, lengthy travel times, the limited nearby accommodation, 18 and the potential lack of a collegiate social atmosphere away from home institutions. These are challenges for the laboratory directors but arguably worse in some cases are the environmental challenges, particularly in Europe now, where all four deep sites are in national parks. This has, for instance, restricted surface laboratory development at Boulby and at Gran Sasso has halted expansion plans in part due to the environmental impact on the local water table. All site developments increasingly need to take account of environmental impacts. More importantly, site location is vital to certain science activity, notably neutrino physics. Here, if the best neutrino oscillation physics is to be extracted then the distance to a potential next-generation neutrino beam or factory needs to be optimized, depending on the beam energy. Long baselines favor better separation of matter effects from CP violation and provide a richer neutrino physics, including determining the MNSP matrix elements, especially θ13 [9]. This factor has, for instance, been an issue for Soudan, being rather too close to Fermilab (724 km) and conversely provided encouragement for the development of Phyasalmi, where the distance to CERN (2,300 km) makes this attractive. Conversely, the proximity of Frejus to CERN (130 km) may disfavor this site. This matter was a consideration for DUSEL where the chosen site of Homestake is at 1,290 km from Fermilab and 2,540 km from BNL. The relative remoteness of a site like Phyasalmi or SNOLAB, away from commercial nuclear energy reactors is also a consideration. The anti-neutrino background from these is, for instance, a limiting factor for new experiments seeking to observe the background neutrino flux from past supernova, while in the new field of geo-neutrinos location in relation to the local thickness of the Earth’s crust is an issue [10]. Science and Expansion—Hooray for Proton Decay There has been outstanding success recently in underground physics, most obviously in solving the solar neutrino problem, with SNO at SNOLAB, at SuperK and Gran Sasso, but also with neutrino beam experiments, and in dark matter and double beta decay, where it has proved possible to build ever larger and more sophisticated experiments underground. Table 2 lists most of the current activity. The recent success of Borexino at Gran Sasso (see Figure 3) is a particular milestone, not just for successfully observing 7Be solar neutrinos in real time but because this experiment has demonstrated the feasibility of achieving backgrounds in a large (87.9 ton, fiducial) active medium, liquid scintillator in this case, at the Nuclear Physics News, Vol. 18, No. 4, 2008 feature article exceptional level of 7 × 10−18 g/g 323Th—a value once thought impossible [11]. This progress, together with rapid development of new technologies, such as very large liquid noble gas detectors, notably liquid argon, plus better understanding of how to build large caverns at depth, points the way to a far more ambitious future. The pinnacle here would be construction of a 100– 1,000 Kton experiment (~20 times SuperK) that would push proton decay sensitivity by one to two orders, including in the kaon channels [5]. However, such a detector could also measure the relic neutrino flux from past supernovae for the first time; observe neutrino bursts from new supernovae; geo-neutrinos and, with a suitable beam, unravel lepton CP violation and measure θ13 to exceptional precision. In Europe the LAGUNA collaboration, now partly funded by the European Commission, will study three potential technologies—water cherenkov, liquid argon, and liquid scintillator—and investigate options for an underground site. Six are being considered—Boulby (UK), Canfranc (Spain), Frejus (France), Phyasalmi (Finland), Slanic (Romania), and Sunlab (Poland) (see Table 2). Work has started with engineers and companies to determine the safe size and form of caverns that could be built at each site. LAGUNA is Europe’s answer to similar megaton activity in Asia and North American. DUSEL at Homestake would now be the location for a U.S. version. In Japan, plans for HyperK are well advanced with detailed rock studies in the region of Kamioka mine already completed [12]. However, in this region there is potential interest in a large detector further downstream from the Tokai neutrino beam as part of extensions to the current T2K experiments. Such a detector could be lined up with SuperK and located in South Korea or, as recently proposed, on the Japanese island of Okinoshima [13]. Although likely costing a fraction of CERN’s LHC, the scale of a nucleon decay facility means probably only one site will ever see such an experiment. However, the vibrancy in underground science in general is seeing growth now anyway, with new sites emerging, such as the recently funded Indian Neutrino Observatory (INO), and many expansions underway (see Table 2). The drive for much of this is new dark matter and neutrino experiments, including for double beta decay. These fields are maturing and now developing a new generation of larger, multi-ton, experiments with more sophisticated background reduction. In Europe, the new Canfranc halls have recently been built with this in mind and at Frejus, the deepest in Europe, ULISSE is well advanced to establish two new halls totalling >3000 m2, made possible by the highway agency’s need to excavate a new emergency evacuation tunnel. One of these halls is proposed to have an integrated water shield to provide the ultimate low background room, possibly the quietest place in the Universe [8]! All the LAGUNA sites in fact have general expansion plans. At Boulby for instance, the mine company is proceeding into new deeper hard rock areas with new science laboratories to be made available, starting with a dedicated geophysics laboratory. At Phyasalmi, now the deepest mine in Europe at 1400 m, engineers are proposing a new facility separated from the main mining activity. Perhaps the bestknown expansion activities are at SNOLAB and DUSEL. The Canadian site is nearing completion of an exceptional facility that includes the first purpose-built underground laboratory for experiments using cryogenic liquids, the Cryopit Laboratory (see Figure 4). In the United States, although DUSEL, as the world’s largest currently planned new site, will need final congressional approval, the first stage is proceeding anyway thanks to state donations and funds from local philanthropist Mr. T. Denny Sanford (SUSEL). This will see rapid restoration of the original cavern at Homestake used by Ray Davis to make his detection of neutrinos from the Sun—a fitting tribute to his pioneering work in one of the original Deep Underground Laboratories. Acknowledgments The author thanks ILIAS (contract no. RII3-CT-2004506222) and CPL (Boulby) and LAGUNA for support. Figure 4. Schematic plan of the new SNOLAB expansions showing the SNO cavern (left), new laboratories (blue), and further extension for the Cryopit laboratory (top right). Vol. 18, No. 4, 2008, Nuclear Physics News 19 feature article References Q2 1. www.lbl.gov/nsd/homestake/ 2. L. Kaufmann et al., Nucl. Phys. B—Proc. Supp. 173 (2007), 141. 3. A. Bettini, Proc. TAUP2007, www.iop.org/EJ/volume/ 1742-6596/120/8 4. M. Laubenstein et al., App. Rad. & Isotopes 61 (2004), 167. 5. J. Aysto et al., JCAP 0711 (2007), 011. 6. www-ilias.cea.fr 7. E. Tziaferi et al., Astroparticle Phys. 27 (2007), 326. 8. www-lsm.in2p3.fr/ 9. V. Barger et al., arxiv.org/abs/0705.4396 10. A. Kathrin et al., Astroparticle Phys. 27 (2007), 21. 11. C. Arpesella et al., Phys. Lett. B 658 (2008), 101. 12. N. Wakabayashi, proc. NNN07, www-rccn.icrr.u-tokyo.ac.jp/ NNN07 13. A. Rubbia et al., arXiv:0804.2111. NEIL SPOONER University of Sheffield and Boulby Laboratory 20 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods JUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei International collaborations fill today’s research landscape, facilitate scientific progress, and lead to a stronger scientific community through tackling mutually beneficial research problems. Furthermore, international research collaborations result in a cultural understanding among the community of scientists. For these general reasons, the Japan U.S. Theory Institute for Physics with Exotic Nuclei (JUSTIPEN) was established two years ago. JUSTIPEN enables travel of U.S. scientists to Japan to collaborate with their Japanese counterparts as the community pursues a basic understanding of exotic nuclei and their role in astrophysics and other areas. In this brief report, I will describe the activities of JUSTIPEN during the last two years. Experimental and theoretical studies are now underway to attain a deeper understanding, richness, and diversity of nuclear phenomena. Key scientific themes that are being addressed are captured by five overarching questions that have been developed during the last few years. These are: • • • • • What is the nature of the nuclear force that binds protons and neutrons into stable nuclei and rare isotopes? What is the origin of simple patterns in complex nuclei? What is the nature of neutron stars and dense nuclear matter? What is the origin of the elements in the cosmos? What are the nuclear reactions that drive stars and stellar explosions? These questions align well with the drivers of rare isotope science. One primary aspect of the first and second questions concerns testing the predictive power of models by extending experiments to new regions of mass and proton-to-neutron ratio and identifying new phenomena that will challenge existing many-body theory. In order to achieve the overarching goal of a comprehensive description of all nuclei, a new generation of rare isotope facilities is coming on-line to produce very short-lived nuclear species in the laboratory. Notable among these new facilities are the Rare Isotope Beam Factory at RIKEN in Japan, which began operations in November 2006, the Facility for Antiproton and Ion Research (FAIR) facility at GSI which is under construction, and isotope separation techniques, which continue to be developed at SPIRAL-II, Ganil in France, and TRIUMF in Canada. These new facilities, in addition to existing experimental efforts at premier facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University and the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL), and including the proposed Facility for Rare Isotope Beams (FRIB) in the United States, hold the key to unlocking the mystery of nuclei and nuclear production in the universe. Theoretical investigations of nuclei and their applications will also benefit from experiments at current and new facilities, and a group of Japanese and U.S. scientists realized that an enhanced theoretical collaborative activity between the United States and Japan would benefit both countries in this area of science. The U.S. contribution through the U.S. Department of Energy JUSTIPEN grant provides travel and local support for U.S. scientists to visit scientists in Japan involved in the study of nuclei. Meanwhile, the University of Tokyo (abbreviated as Todai in Japanese) and RIKEN have established the TodaiRIKEN Joint International Program for Nuclear Physics (TORIJIN) in order to enhance jointly international collaborations and exchanges in nuclear physics, and the University of Tokyo has created an associate professor position designated for this purpose. One of the major purposes of TORIJIN is obviously to host the JUSTIPEN activities including the JUSTIPEN office in the RIBF building of the RIKEN Nishina Center and various cares for JUSTIPEN visitors. While this office is the hub of JUSTIPEN activities, we also provide support for travel to other Japanese venues for collaborative research. Detailed information on JUSTIPEN can be found at the Web page www.phys.utk.edu/JUSTIPEN. This website provides a repository of information for JUSTIPEN including visitor information, exit reports, detailed information on how to function at RIKEN, JUSTIPEN policies, and other items. JUSTIPEN Opening, July 10–11, 2006 JUSTIPEN was opened during mid-July, 2006. Members of the U.S. Vol. 18, No. 3, 2008, Nuclear Physics News 21 facilities and methods team on this trip included Steering Committee members Witek Nazarewicz (University of Tennessee), Baha Balantekin (University of Wisconsin), Richard Casten (Yale University), and David Dean (ORNL), as well as Sidney Coon (U.S. Department of Energy Office of Nuclear Physics Theory Program Manager), and Bruce Barrett (U. Arizona, and one of the initial long-term visitors to the Institute). Also attending the meetings were many Japanese colleagues; a partial list is given with the official picture of the opening, shown in Figure 1. During July 10, talks were given to explore what kinds of scientific collaborations could come from the Institute. Numerous ideas were put forward for the JUSTIPEN efforts. Policy was also discussed at the meeting. During its first year of operations, JUSTIPEN provided funding to 10 U.S. visitors and to approximately 25 visitors during its second year. JUSTIPEN-U.S. During this time, Japanese colleagues also worked toward establishing funding opportunities to send Japanese to the United States for collaborations. This effort brought them with the “International Research Network for Exotic Femto Systems (EFES)” as a Core-to-Core project by the Japan Society for the Promotion of Science (JSPS). The EFES project played major strong roles as Japanese matching fund to Figure 1. JUSTIPEN OPENING (L to R): N. Itagaki (University of Tokyo, secretary of JUSTIPEN); H. Sakai (University of Tokyo, JUSTIPEN governing board); T. Motobayashi (RIKEN, JUSTIPEN Associate Director); W. Nazarewicz (University of Tennessee and ORNL, JUSTIPEN governing board); Y. Doi, (Executive Director of RIKEN); R. Casten (Yale University, JUSTIPEN Governing Board); B. Barrett (U. Arizona, first long-term visitor of JUSTIPEN); D. Dean (ORNL, JUSTIPEN Associate Director); B. Balantekin (U. Wisconsin, JUSTIPEN governing board); S. Coon (U.S. DOE Office of Science, Office of Nuclear Physics); A. Arima (President, Japan Science Foundation); Y. Yano (Director, Nishina Center for Accelerator Sciences, RIKEN); T. Otsuka (U. Tokyo, JUSTIPEN Managing Director); M. Ishiara (RIKEN); and Y. Okuizumi (RIKEN, head of Nishina Center Administration). 22 Nuclear Physics News, Vol. 18, No. 4, 2008 JUSTIPEN, called for short as JUSTIPEN-U.S. hereafter. The EFES initiative resulted in an exchange activity in March 2007. The first Joint JUSTIPEN-LACM Meeting was held at the Joint Institute for Heavy Ion Research (JIHIR) at ORNL from March 5–8, 2007. The meeting was a merger of two workshops: (1) the annual National Nuclear Security Administration–Joint Institute for Heavy Ion Research (NNSA–JIHIR) meeting on the nuclear large amplitude collective motion (LACM) with an emphasis on fission, and (2) the U.S.–Japan theory meeting under the auspices of JUSTIPEN. The purpose of the meeting, jointly organized by the JUSTIPEN Governing Board, by the UT/ORNL nuclear theory group, and by the EFES, was to bring together scientists (theorists and experimentalists) with interests in physics of radioactive nuclei, LACM, and theoretical approaches related to the Scientific Discovery through Advanced Computting (SciDAC) Universal Nuclear Energy Density Functional (UNEDF) project (see Figure 2). The meeting consisted of approximately 50 talks on physics of radioactive nuclei. Figure 2 includes local organizers of the workshop and the Japanese colleagues. The Tandem of the Holifield Radioactive Ion Beam Facility (HRIBF) at ORNL stands in the background. The success of the 2007 meeting led to a second meeting during 2008. The second LACM-EFES-JUSTIPEN Workshop was held during January 23–25, 2008, at ORNL. The workshop program covered a number of topics including fission/fusion and other forms of large-amplitude collective motion, computational nuclear structure physics, nuclear structure relevant facilities and methods to nuclear astrophysics, gamma-ray spectroscopy, clustering in nuclei, and topics related to ongoing and future collaborations with Japanese groups and colleagues. This meeting ran concurrently with a celebration of the 25th anniversary of the building of the Joint Institute for Heavy Ion Research (JIHIR) at ORNL. The JIHIR was the brainchild of a group of physicists, including University of Tennessee professor (and former ORNL deputy director) Lee Riedinger, UT’s Carroll Bingham, and Vanderbilt University’s Joe Hamilton, to establish a means to open the Lab’s Holifield Facility and its tools such as the Recoil Mass Spectrometer to university users back in 1982. JUSTIPEN was the linchpin to obtain full funding for an expansion of the JIHIR to obtain a new “theory wing.” This expansion will enable a reciprocal Japanese exchange program that will bring our Japanese colleagues to the United States, again to benefit research efforts in physics with exotic nuclei. Funding for this expansion will come from the State of Tennessee, ORNL, the University of Tennessee, and Vanderbilt University. Construction began in the spring and is now about 50% complete. We anticipate opening the theory wing in the winter. The extension to the JIHIR will be the home-base for the JUSTIPEN-U.S. program and will consist of 4 singleperson offices and 4 two-person offices. A Brief Tour of the Physics of Exotic Nuclei Research performed through JUSTIPEN is meant to be broad and encompasses a variety of theoretical techniques (see Figure 3). In this closing section, I will briefly mention some of the aspects of that research. Theoretical research of the properties and characteristic of nuclei necessarily involves coming to an understanding of the complexity of the nuclear force, which involves two-body and threebody (at least) interactions among protons and neutrons, and an understanding of how to apply quantum many-body theory to the nuclear problem. Recent advances in chiral effective field theory, using the pion and nucleon as the relevant degrees of freedom, have connected the nuclear forces to the underlying symmetries of QCD, and are able to accurately describe nucleon-nucleon scattering phase shift information. The formulation of the nuclear forces through effective field theory yields a series of Feynman diagrams with an order parameter that is a ratio of the momentum transfer in scattering and a momentum cut-off parameter, usually taken to cover the range of scattering data up to about 500 MeV. At the third order in the expansion, three-body forces appear. This should come as no surprise as nucleons are not point-like fundamental particles, but are made up of quarks and gluons. For many years we have understood that a threebody force must be active in nuclei as no two-body interaction, whether derived from effective field theory or from meson theory, has ever been able to simultaneously fit all nucleonnucleon scattering data, the deuteron binding energy, and the masses of the triton and alpha particle. A more complete understanding of the nuclear force represents an important avenue of research for the physics of nuclei. As Maria Geoppert-Mayer said in her Nobel Lecture, “[T]he first, the basic approach, is to study the elementary particles, their properties and mutual interaction. Thus one hopes to obtain knowledge of the nuclear forces. If the forces are known, one should, in principle, be able to calculate deductively the properties of individual nuclei. Only after this has been accomplished can one say that one completely understands nuclear structure” [1]. We certainly do understand the nuclear force better today than we did in 1965, which has led to substantial progress in developing ab initio approaches to calculate nuclei. Pioneering efforts using a meson-theory-inspired interaction, including three-body forces, has been carried out using Greens Function Monte Carlo approaches. Nuclear spectra Figure 2. First JUSTIPEN-LACM Meeting, March 2007. Vol. 18, No. 4, 2008, Nuclear Physics News 23 facilities and methods Figure 3. The figure shows the nuclei in the N,Z plane over layed with theoretical approaches being developed to understand all nuclei. are reproduced from the deuteron into mass 12 nuclei. Basis expansion methods have also produced exciting results in light nuclei. Coupled-cluster techniques are being used to investigate the nature of closed-shell nuclei into the Calcium and Nickel region. Although space does not permit me to discuss these advances in detail, I believe we have entered the era of precision ab initio calculations of certain nuclei. At the same time, we have witnessed an increasing understanding of medium mass nuclei through advances in the nuclear shell model. Here effective interactions derived from nuclear spectroscopic information in, for example, the fp-shell (with 40Ca as a closed core), have enabled a wide description and codification of nuclear ground and excited state information. Shell model calculations take on various forms, including standard diagonalization and Monte Carlo implementations, and are widely utilized by experimental colleagues. For those nuclei at or very near the neutron drip-line, inclusion of continuum single-particle states (scattering 24 states, resonant states, and the nonresonant continuum) is necessary for the proper description of these nuclei. Derivation and implementation of shell-model technology to incorporate Gamow single-particle basis states can be used to describe these very weakly bound systems and opens the door to theoretical investigations of the challenging problems associated with open quantum systems. Coupled-cluster theory using Gamow-basis states was recently implemented to calculate widths of and binding energies of the Helium isotopes. To reach the heavier nuclei we turn to nuclear density functional theory (DFT), which utilizes both matter and pairing densities to produce information on the properties of nuclei. The list of topics covered in this area includes substantial research on the methods, the forces, extensions for excited states, projection to good quantum numbers, fission mechanisms for heavy nuclei, and timedependent phenomena, all of which are important for the development of nuclear DFT. Nuclear Physics News, Vol. 18, No. 4, 2008 A comprehensive theory of nuclei would be incomplete without reaction theory, and progress in this arena in light nuclear systems ties nicely with efforts in ab initio calculations. Recently the Greens Function Monte Carlo collaboration calculated neutron-alpha phase shifts and found that the three-body force affects these, and No Core Shell Model group calculated 7Be(p, γ)8B cross-section as a function of center-of-mass energy. These efforts point to an interesting future for reaction theory in light nuclei. Improvements in the nuclear density functional approach should also lead to a more complete description of optical potentials for nuclear scattering. Another line of research involves understanding the simplicities, or symmetries, found in nuclear spectra and relating those to the underlying quantum many-body problem of the nucleus. Numerous simplicities in nuclear spectra can be described by invoking symmetry arguments. These efforts will be particularly useful in approaching neutron-rich mid-shell nuclei where symmetries such as X(5) are believed to exist. Nuclei are produced in stars and nuclear astrophysicists seek to understand how nuclear processes have shaped the cosmos, from the origin of the elements, the evolution of stars, and the detonation of supernovae, to the structure of neutron stars and the nature of matter at extreme densities. The collaborations in this area cover astrophysical observations and, also, astrophysical simulations as nuclear data (and theoretical calculations) are utilized in simulations ranging from nucleonsynthesis to stellar explosions. Sensitivity studies indicate that certain nuclear processes are very important for these processes and facilities and methods point to the need for experimental efforts on specific reaction rates. Conclusion and Perspective In conclusion, the initial years of JUSTIPEN lead one to believe that the exchange activity will prove to be very fruitful indeed. JUSTIPEN affords significant opportunity for U.S. and Japanese scientists to collaborate on numerous projects related to exotic nuclei. Reciprocating visits of Japanese and U.S. scientists will enhance our understanding of both nuclei and bring a broad benefit to both nations. The major goal of JUSTIPEN is to deliver an international venue for research on the physics of nuclei during an era of experimental investigations on rare isotopes. We are now at the two-year anniversary of this effort, and look forward to a continuing productive scientific endeavor that will enhance international collaborations in the areas of the physics of nuclei and nuclear astrophysics where unstable nuclei play an important role. Reference 1. M. Goeppert Mayer, in Nobel Lectures, Physics, 1963–1970, Elsevier, Amsterdam (1972), available at http:// nobelprize.org/nobel_prizes/physics/ laureates/1963/mayer-lecture.html DAVID J. DEAN Oak Ridge National Laboratory Oak Ridge, Tennessee, USA Vol. 18, No. 4, 2008, Nuclear Physics News 25 facilities and methods Compass and the Nucleon Spin Puzzle The COMPASS Spectrometer The COMPASS (COmmon Muon and Proton Apparatus for Structure and Spectroscopy) experiment has been in operation at CERN since 2002, carrying on an ambitious experimental program on the spin structure of the nucleon and on hadron spectroscopy. The spin structure of the nucleon has been investigated by impinging a 160 GeV/c momentum m+ beam on solid polarized targets. In 2002, 2003, 2004, and 2006 a polarized deuteron target (6LiD) was used, while in 2007 data were collected on a NH3 polarized proton target. In this article I will focus on the contribution of COMPASS to the problem of the nucleon spin. I will not mention the hadron program, searching for glueballs and exotics in central production and diffractive processes, which just started in 2008, with a first run with a 190 GeV/c momentum pion beam scattering off a liquid Hydrogen target. A worldwide effort, both theoretical and experimental, has been devoted to the understanding of the origin of the nucleon spin during the past twenty years. Excellent reviews exist on the physics case.1 Here I will try to outline only the general terms of the problem, giving a short account of our contribution. The apparatus we have used for the muon beam program consists of a two-stage magnetic spectrometer, 60 m long, which allows the reconstruction of trajectories and momenta of the incoming and scattered muons and of the produced hadrons. Charged particles are identified by a RICH 1 See, for instance, Ref. [1] for the longitudinal spin; Ref. [2] for the transverse spin. 26 (Ring Imaging CHerenkov) counter and by hadron calorimeters. The target material is contained in two 60-cmlong cells, which are polarized by dynamic nuclear polarization in opposite directions, so that data from both spin directions are recorded at the same time. Since 2006, a new target magnet has been used, increasing the acceptance from ±70 mrad to ±180 mrad. Also, the target material has been distributed in three cells, and polarized as + − + or − + −. The full description of the spectrometer can be found in Ref. [3], whereas Figure 1 gives an artistic view. Data have been collected both in the longitudinal target mode (polarization direction parallel to the beam) and in the transverse mode (target polarization orthogonal to the beam direction). The “Spin Crisis” Protons and neutrons constitute 99.9% of the material world we live in, but it is fair to say that we still lack a full description of their internal structure. Since the pioneering experiments at SLAC in the late 1960s, deep inelastic scattering (DIS) is the standard technique to investigate the structure of the nucleon. Using polarized lepton beams and polarized targets the spin structure of the nucleon can be investigated. If both the beam and the target spins are aligned along the direction of the incident lepton, one structure function, g1, can be measured from the cross-section asymmetry of the inclusive scattering. In the quark parton model this structure function can be written as g1 ( x ) = 1 2 ∑ e2 q q ⋅ Δq( x ) Nuclear Physics News, Vol. 18, No. 4, 2008 where Δq( x ) = [q↓↑ ( x ) + q ↓↑ ( x )] − [q↑↑ ( x ) + q ↑↑ ( x )] are the differences of the quark densities with quark spin antiparallel and parallel to the target nucleon spin. The quantity x is the Bjorken variable, the fraction of the nucleon momentum carried by the target parton. Integrating g1(x) from 0 to 1 one obtains a linear combination of the three light quarks first moments Δq = ∫ 1 Δq( x ) dx . Using additional information from the neutron betadecay and from hyperons strangeness changing decay, which provide two linear combinations for 䉭q’s, (䉭u−䉭d) and (䉭u + 䉭d − 2䉭s), respectively, it is possible to extract 䉭Σ = 䉭u + 䉭d + 䉭s. The quantity 䉭Σ can be interpreted as the contribution of the quarks to the spin of the nucleon, which in general terms can be written as 0 1 1 = ΔΣ + ΔG + Lq + LG . 2 2 In this expression, 䉭G is the contribution of the gluons, and Lq,G are possible contributions from the gluons and quarks angular momenta. In the simple quark model the three valence quarks are in an S-state, so Lq = 0. There are no gluons, so that 䉭G = 0 and LG = 0, thus the spin sumrule is satisfied by 䉭Σ = 1. The first measurements of polarized electron-proton scattering were performed at SLAC in the 1980s by the E80 and E130 Collaborations, and yielded results that were consistent with expectations. A breakthrough occurred when the European Muon Collaboration (EMC) at CERN extended these measurements to a much larger kinematic range, by using facilities and methods a polarized muon beam with an energy 10 times higher than at SLAC. In 1988 the Collaboration reported [4] that 䉭Σ = 0.12 ± 0.09(stat) ± 0.14(syst), that is, a small value, even compatible with zero. A major surprise that soon came to be known as the “spin crisis.” Actually, the inadequacy of the static quark model should have been realized well before the execution of the EMC experiment, but very likely the major achievements of the quark model had cast a shadow on this point. In particular, the amazing success of the static quark model in explaining the magnetic moments of the baryons (three valence quarks in an S-state SU(6) wave-function, with Dirac magnetic moment and about 340 MeV/c2 mass) undoubtedly contributed to radicate in our minds the idea that the proton spin is carried by the quarks. Several other polarized DIS experiments on the proton, the deuteron, and 3He, have confirmed the EMC result. All these experiments (including COMPASS) allow us now to accurately determine 䉭Σ, the contribution of both valence and sea quark spins to the nucleon spin, to be only 30%. Actually, g1(x) and 䉭q(x) are also functions of Q2, the square of the mass of the virtual photon that is exchanged in the process, and G(x, Q2) and 䉭q(x, Q2) mix up in the evolution equations of QCD, so that the extraction of the first moments requires a full QCD fit. However, it was already clear in the mid-1990s that a better understanding of the nucleon spin structure demanded separate measurements of the missing contributions, that is, the gluon polarization 䉭G/G and Lz. In particular, several theoretical analyses suggested a large contribution 䉭G as a solution to the spin Figure 1. Artistic view of the COMPASS spectrometer. crisis. To single out this contribution, a new experimental approach was necessary, namely semi-inclusive DIS with the identification of the hadrons in the current jet. A flavor tagging procedure allows us to then identify the struck parton, and thus to separately determine 䉭q,䉭q, and 䉭G. A suggestion to isolate the photon-gluon fusion (PGF) process g*g → qq and measure 䉭G directly had already been put forward a few years before, and implied measuring the cross-section asymmetry of open charm production in DIS. A new experiment, with full hadron identification and calorimetry, therefore seemed to be necessary, and COMPASS was proposed to CERN in 1996. The Case for Transversity In parallel to the necessity of direct measurements of 䉭G/G, semi-inclusive DIS seemed to be the best tool to investigate transverse spin phenomena. As a matter of fact, the knowledge of the helicity distributions 䉭q(x) and 䉭G does not exhaust the spin structure of the nucleon. It had been realized in 1991 that to fully specify the quark structure of the nucleon at the twist-two level, the transverse spin distributions 䉭Tq(x) must be added to q(x) and to 䉭q(x) [5]. The definition of 䉭Tq(x) is analogous to that of 䉭q(x), but it refers to transversely polarized quarks in a transversely polarized nucleon. Since rotations and Lorentz boost do not commute, helicity and transversity are expected to be different. 䉭Tq(x) gives a measure of the correlation between the transverse quark spin and the transverse nucleon spin. Being chiralodd, transversity cannot be measured in inclusive DIS (the hard process conserves chirality) but only in a process in which it combines with another chiral-odd quantity. Transversity can be extracted from measurements of single-spin asymmetries in cross-sections for semi-inclusive DIS (SIDIS) of leptons on transversely polarized nucleons, in which hadrons are also detected in the final state. In this process the second chiralodd object is the fragmentation function. It was conjectured in 1993 [6] that there could be a correlation between the spin of a transversely polarized quark and the kT of the hadron into which the quark fragments. Vol. 18, No. 4, 2008, Nuclear Physics News 27 facilities and methods This part of the fragmentation function is usually named Collins function (䉭T0 Dqh ). In the hadronization of a transversely polarized quark a nonzero Collins function would be responsible for a left–right asymmetry of the hadrons with respect to the plane defined by the quark spin and momentum directions. In SIDIS on a transversely polarized nucleon, a nonzero 䉭T0 Dqh , in conjunction with 䉭Tq, would cause a left–right asymmetry of the resulting hadrons with respect to the plane defined by the struck quark spin (i.e., the nucleon spin, reflected about the normal to the scattering plane) and the virtual photon direction. In this case the measurable asymmetry, the so-called Collins asymmetry, AColl, is the convolution of 䉭Tq and of 䉭T0 Dqh , and has originally been suggested as a possible way to measure transversity. The transversity distribution and the Collins function are two examples of correlations (quark spin and nucleon spin, quark spin and fragmentation hadron kT respectively), which recently have been recognized as being crucial for understanding the spin structure of the nucleon in terms of the quark and gluon degrees of freedom of QCD. Particularly important are the transverse momentum dependent (TMD) parton distribution and fragmentation functions. These functions are time-reversal odd (T-odd) functions, and as such are of particular importance as they can generate single-spin asymmetries. Large singlespin asymmetries in hadron-hadron collisions have been known for many years, and have been measured even recently at RHIC, and a large-scale effort is ongoing to provide in the framework of QCD a unified description of both the SIDIS and the hadronhadron transverse spin asymmetries. 28 The Sivers distribution function, 䉭T0q(x) [7], is probably the most famous TMD distribution function. Allowing for a correlation between the nucleon spin and the intrinsic KT of the quark, the distribution of the hadrons resulting from the quark fragmentation might exhibit a left–right asymmetry (usually called the “Sivers asymmetry” ASiv) with respect to the plane defined by the nucleon spin and the virtual photon direction. In this case the observable is the product of the Sivers DF and the FF. Measuring SIDIS on a transversely polarized target allows the Collins and the Sivers effects to be disentangled. Investigation of the transverse spin phenomena in SIDIS is complementary to the investigation of longitudinal spin phenomena. A spin sum-rule can also be written for the transverse spin case [8] 1 1 = 2 2 ∑ q ΔT q + Lq . The gluon contribution being absent in the transverse case, from the knowledge of direct information on the size of the orbital angular momentum can be derived. COMPASS Results on Longitudinal Spin In this short report I will concentrate only on the measurements of g1 and of 䉭G/G, and will skip all the other results COMPASS has obtained in the longitu- dinal target polarization mode (from the flavor separated helicity distributions, to L-physics and to vector meson-physics). To directly measure 䉭G two procedures have been followed to tag the PGF process. The first one consists in selecting open-charm events, which provide the purest sample of PGF events, but at a low rate. Open-charm events are identified by reconstructing D0, D0, D*+ and D*− mesons from their decay products. The full 2002– 2006 data set has been analyzed and the preliminary results are given in Table 1, where m2 is the QCD scale. A second option is to select events with two high-pT hadrons (with respect to the virtual photon direction), as tags of the two jets from the hadronization of the qq pair. The latter procedure provides much larger statistics but leaves a significant fraction of background events in the selected sample, which has been estimated with sophisticated MonteCarlo simulations. DIS events (Q2 > 1 (GeV/c)2) and low Q2 events are considered separately, and different generators are used as reliable models for the interaction of the virtual photon with the nucleons. Results from the Q2 < 1 (GeV/c)2 data collected in the years 2002–2003 have already been published [9]. A preliminary value for 䉭G has been extracted from the whole set of 2002, 2003, 2004 deuteron data, and it is given in Table 1. Table 1. COMPASS results for the direct measurement of 䉭G/G. Method 䉭G/G Statistical error Systematic error GeV/c2 Open charm − 0.49 ± 0.27 ± 0.11 0.11 13 + 0.08 ± 0.10 ± 0.05 0.082 3 + 0.016 ± 0.058 ± 0.055 0.085 3 high-pT events, Q2 > 1 2 high-pT events, Q < 1 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods normalization scheme and obtained for the singlet moment at Q2 =3 (GeV/c)2 䉭Σ = 0.30 ± 0.01(stat) ± 0.02(evol). Figure 2. The asymmetry Ad1 as measured in COMPASS [10] and previous results from SMC [11], HERMES [12], SLAC E143 [13], and E155 [14] at Q2 >1 (GeV/c)2. A similar analysis has been performed for the SIDIS events (Q2 > 1 (GeV/c)2). A preliminary analysis of the data collected in 2002, 2003, and 2004 has provided the results shown in Table 1. The COMPASS experiment has also measured with high precision the longitudinal virtual photon asymmetry Ad1 of the deuteron. Figure 2 gives the COMPASS measurement, which refers to 2002, 2003, 2004 and has been recently published [10], compared with previous measurements [11–14]. At small x (x < 0.03) the COMPASS data exhibit errors that are considerably smaller than the previous SMC results, which is of great relevance when extrapolating the data to x=0 to evaluate the first moment of g1. From Ad1 the structure function gd1 of the deuteron is obtained g1d = d photoabsorption cross-section. Using all the available gd1 data, we have performed a QCD fit [10] in the MS The same fit provides estimates for 䉭G(x) and for its first moment. Two different solutions are equally acceptable, one with 䉭G(x) > 0 and the other with 䉭G(x) < 0. Figure 3 shows the distributions of the gluon polarization that results from the two fits. The conclusion from the fit is that the first moment of 䉭G(x) is of the order of 0.2–0.3 in absolute value at Q2 = 3(GeV/c)2. Also shown in Figure 3 are our direct measurements from Table 1, as well as the published results [15] and the recent preliminary value [16] from the HERMES Collaboration, and the F2d A1d 2 x(1 + R) where F 2 is the spin-independent deuteron structure function and R is the ratio of longitudinal and transverse Figure 3. Distribution of the gluon polarisation 䉭G(x)/G(x) at Q2 = 3(GeV/c)2 for the two QCD fits with 䉭G > 0 and 䉭G < 0 performed by the COMPASS Collaboration. The data points show the measured values from SMC [17], HERMES [15, 16], and COMPASS (Table 1). Vol. 18, No. 4, 2008, Nuclear Physics News 29 facilities and methods between 䉭Tu and 䉭Td. A few analyses aiming at the extraction of the transversity distributions have already been performed, and all the observed phenomena can be described in a unified scheme. In Figure 4 the results of our measured deuteron asymmetries are compared with the results of the most recent global analysis of Anselmino et al. [21] which uses the Collins asymmetries from HERMES (proton) and from COMPASS (deuteron), and the e+ e− → hadrons data from BELLE to fit the valence u- and d-quark distributions 䉭Tuv, 䉭Tdv, and the Collins functions 䉭T0 Dqh for favored and unfavored fragmentation (9-parameter fit). In Figure 5 the Figure 4. COMPASS results for p± Collins asymmetries [18] on deuteron from the 2003 and 2004 runs compared with the fit results of the global analysis of Anselmino et al. [21]. result from the SMC Collaboration [17]. The picture that emerges clearly favors small values of 䉭G, a conclusion supported also by the recent measurements at RHIC. COMPASS Results on Transverse Spin The COMPASS experiment has measured for the first time single hadron transverse spin asymmetries in DIS of high energy muons on deuterons and protons, scattering the 160 GeV/c muon beam on transversely polarized 6 LiD and NH3 targets. Also in this case, several asymmetries have been investigated, in particular for a two hadron system, exclusive r, and l hyperons, but in this short report I will mention only the results for Collins and Sivers effects. Collins asymmetries definitely different from zero have been reported 30 for a few years by the HERMES Collaboration, measuring semi-inclusive DIS events on a transversely polarized proton target, providing evidence that both the transversity PDF and the Collins FF are different from zero. Independent evidence that the Collins mechanism is a real measurable effect has come from the recent analysis of the BELLE Collaboration. Our measurements on the deuteron do not show any appreciable effect, and all the measured asymmetries are compatible with zero, as apparent from Figure 4, which shows our latest results for p± [18] from the 2003 and 2004 runs (the Collins and Sivers asymmetries on the deuteron for nonidentified hadrons from the 2002, 2003, and 2004 data have already been published [19, 20]). The deuteron being isoscalar, the null result from COMPASS can be understood in terms of cancellation Nuclear Physics News, Vol. 18, No. 4, 2008 Figure 5. The transversity distributions 䉭Tqv for the u- and d-quarks extracted with a global analysis of all the existing data by M. Anselmino et al. (lower red curves). The dotted curves are the corresponding helicity distributions and the blue curves indicate the so-called Soffer bound. facilities and methods extracted transversity distributions 䉭Tqv for the u- and d-quarks are plotted and compared to the corresponding helicity distributions. This is the first time the transversity distributions are extracted with a global analysis of all the existing data, but it is already possible to note that the transversity distributions (in particular the d-PDF) are considerably smaller than the corresponding helicity distributions, and do not saturate the so-called Soffer bound. Most rewarding is the comparison of our very recent preliminary results of the Collins asymmetry of the proton [22] with the expectations from the same global analysis. The comparison between our new data and the predictions of Ansemino et al. is shown in Figure 6. The agreement is very good, and a clear sign of the soundness of the physics which is behind it. We have also measured the Sivers asymmetry. All the asymmetries we have measured on the deuteron target are small, if any, and compatible with zero. On the other hand, the HERMES p+ data on a proton target have also provided convincing evidence that the Sivers mechanism is at work, and that 䉭T0 u v is different from zero. The approximately zero Sivers asymmetries for positive and negative hadrons observed in COMPASS require 䉭T0 u v ∼ −䉭Todv, a relation that is also obtained in some models, and which anyhow has a simple physical interpretation if the Sivers distortion of the PDF of the nucleon is associated with the orbital angular momentum of the uand d-quarks. The preliminary results from our proton data [22] suggest Sivers asymmetries that are compatible with zero both for negative hadrons and for positive hadrons. The result for positive hadron is only marginally compatible with the finding of HERMES, and has to be understood. Is the Nucleon Spin Puzzle Solved? Twenty years after the EMC measurement, it is fair to say that thanks to a huge theoretical and experimental effort many things have been understood: a. The original measurement suggested that 䉭Σ might have been as small as zero. After a new generation of experiments we know that it is not so; 䉭Σ is measured to be 0.3 with good precision. Accurate comparisons with the predictions of sum-rules (in particular with the fundamental Bjorken sum-rule) have been possible. The interconnection between 䉭Σ and 䉭G and the necessity of full QCD analysis have been clearly established. b. The comparison with the static quark model was misleading. Even starting with three valence quarks in an S-state, the Melosh rotation, which gives the connection between the spin states in the rest frame and in the infinite momentum frame, introduces a nontrivial spin structure and correlations between quark spin and quark angular momentum; c. The possibility that most of the missing spin be carried by the gluon seems ruled out by the present direct measurements of 䉭G. The precision on 䉭G will improve in the next years thanks to the combined analysis of the DIS data and of the polarized protonproton data coming from RHIC, but without a dedicated e-p collider it seems difficult to assess with high accuracy which fraction Figure 6. COMPASS preliminary results of the Collins asymmetry of the proton from 2007 data [22]. The curves are the expectations from the global analysis of Ansemino et al. [21]. Vol. 18, No. 4, 2008, Nuclear Physics News 31 facilities and methods of the nucleon spin is due to the gluon and which is due to the orbital momentum. d. New possibilities to understand the spin structure are offered by the investigation of transverse spin effects. New properties of matter have been unveiled. The Collins effect is there and precise measurements of transversity and of the quark orbital angular momentum are at hand. As it has always been since the discovery of Stern and Gehrlach in 1921, the history of spin is a history full of surprises. References 1. S. D. Bass, Rev. Modern Phys., 77 (2005), 1257. 2. V. Barone et al., Phys. Rep. 359 (202), 1. 32 3. COMPASS Collaboration, P. Abbon et al., Nucl. Instrum. Meth. A 577 (2007), 455. 4. EMC Collaboration, J. Ashman et al., Phys. Lett. B206 (1988), 364; Nucl. Phys. B328 (1989), 1. 5. R. L. Jaffe and X. Ji, Phys. Rev. Lett. 67 (1991), 552. 6. J. Collins, Nucl. Phys. B396 (1993), 161. 7. D. Sivers, Phys. Rev. D41 (1990), 83. 8. B. L. G. Bakker, E. Leader, and T. L. Trueman, Phys. Rev. D70 (2004), 114001. 9. COMPASS Collaboration, E. S. Ageev et al., Phys. Lett. B633 (2006), 25. 10. COMPASS Collaboration, V. Y. Alexakhin et al., Phys. Lett. B647 (2007), 8. 11. SMC Collaboration, B. Adeva et al., Phys. Rev. D58 (1998), 112001. 12. HERMES Collaboration, A. Airapetian et al., Phys. Rev. D71 (2005), 012003. 13. E143 Collaboration, K. Abe et al., Phys. Rev. D58 (1998), 112003. 14. E155 Collaboration, P. L. Anthony et al., Phys. Lett. B463 (1999), 339. Nuclear Physics News, Vol. 18, No. 4, 2008 15. HERMES Collaboration, A. Airapetian et al., Phys. Rev. Lett. 84 (2000), 2584. 16. D. Hasch, HERMES Collaboration., AIP Conf. Proc. 915 (2007), 307. 17. SMC Collaboration, B. Adeva et al., Phys. Rev. D70 (2004), 012002. 18. COMPASS Collaboration, M. Alekseev et al., CERN-PH-EP/2008-002, arXiv:0802.2160 hep-ex.. 19. COMPASS Collaboration, V. Y. Alexakhin et al., Phys. Rev. Lett. 94 (2005), 202002. 20. COMPASS Collaboration, E. S. Ageev et al., Nucl. Phys. B765 (2007), 31. 21. M. Anselmino et al., Phys. Rev. D75 (2007), 054032 and PKU-RBRC Workshop on Transverse Spin Physics, Peking, June 30–July 4, 2008. 22. S. Levorato, COMPASS Collaboration, Transversity 2008, Ferrara, Italy, May 28–31, 2008, arXiv:0808.0086 hep-ex. FRANCO BRADAMANTE University of Trieste and Trieste Section of INFN, Italy impact and applications Industrial PET at Birmingham In the 75 years since the first observation of the positron in cosmicray showers, positron emission tomography (PET) has developed into one of the most powerful diagnostic tools in medicine. For clinical studies, a fluid of interest is labeled with a positron-emitting radioisotope and introduced into the body. By detecting the pairs of back-to-back 511 keV g-rays produced in positron-electron annihilation, a PET scanner builds up a quantitative 3D map of the concentration of this fluid, revealing its uptake by individual organs. For example, a labeled form of glucose is used to map metabolic rate and identify tumors (which metabolize glucose rapidly). A similar approach can be used to study flow inside engineering systems. The 511 keV g-rays are highly penetrating (50% are transmitted through 11-mm steel) so non-invasive measurements can be made on real industrial equipment. The potential of PET for such studies has been explored and developed at the University of Birmingham for over 20 years. Unfortunately PET is a slow technique, Figure 1. Basis of PEPT: tracer particle is located using a small number of back-to-back g-ray pairs. requiring measurement of millions of individual g-ray pairs to reconstruct an accurate 3D image, which makes it unsuited to observing the dynamics of fast flows. For many applications, the alternative technique of positron emission particle tracking (PEPT), developed at Birmingham, proves more useful. In PEPT, a single, radioactively labeled tracer particle is tracked as it moves around inside the system under study. The particle’s instantaneous location is determined by triangulation using a small number of detected pairs of back-to-back g-rays (Figure 1). In principle just two detected pairs provide an estimate of location, since each defines a line passing close to the tracer position. In practice more are required to obtain an accurate location, especially as many of the detected pairs are corrupt, for example because one or both of the grays has scattered prior to detection. Given a large enough sample, the cluster of useful lines that converge on the tracer position can be distinguished from the broad background of lines due to corrupt pairs. An iterative algorithm is used, which starts with a sample of typically 100 pairs, calculates their centroid, then discards the outliers and recalculates using just the remaining pairs. This process continues until all corrupt pairs have been discarded. Figure 2 shows an example of PEPT data, following the motion of a single particle within a fluidized bed. Such systems are widely used in industry for processing granular material: if gas (often air) is blown upward through a bed of particles with sufficient velocity the particles become suspended and the bed moves around like a fluid. The figure shows (a) the track of the particle over a period of a few seconds, (b) the “occupancy” distribution representing the fraction of the run time during which the particle was found in each region, averaged over a period of many minutes, and (c) its average velocity at each position. Assuming that the tracer’s behavior is representative of all the particles in the bed, the time-averaged quantities (b) and (c) should describe the average number density of particles in the bed and their average velocity field. As well as studying granular material, PEPT can also be used to study the behavior of viscous fluids, by introducing a small neutrally buoyant particle as a flow follower. Routinely at Birmingham, the tracer is located 500 times per second (so that a particle moving at 5 m/s is observed at intervals of 10 mm along its path) to a precision of around 1 mm. This work dates back to the early 1980s when Mike Hawkesworth at Birmingham was asked by colleagues from Rolls Royce if he could find a way of imaging the lubricant distribution inside an operating aero-engine. Hawkesworth realized that PET, which was then just starting to be used in medicine, could in principle provide the answer. Simultaneously, Eddie Bateman and his team at the Rutherford Appleton Laboratory had been developing a “positron camera” based on a pair of gas-filled multiwire proportional chambers (MWPCs), which they hoped would provide an inexpensive detection system for medical PET. Instead, this system was developed into a robust camera for performing engineering PET. The camera became operational in 1984, Vol. 18, No. 4, 2008, Nuclear Physics News 33 impact and applications Figure 2. Example of PEPT data, from a spouted fluidized bed: (a) short section of particle track, (b) occupancy and (c) velocity field. and shortly afterward was successfully used to measure PET images of radioactively labeled lubricant inside a small jet engine operating at full power on a testbed. The link with Rolls Royce ended around 1990, but the Birmingham group continued to explore the use of PET in engineering. An early application was to study motion in fludized beds, and PEPT was first developed as a way of observing the motion of large particles within such a bed. In the subsequent 15 years the technique has been refined, and techniques have been developed for labelling a range of tracer particles with sizes down to 100 mm. PEPT has been used by a large number of university groups and by researchers from industries including petrochemicals, pharmaceuticals, food, and minerals processing, to study processes involved in the manufacture of products ranging from pharmaceutical tablets to canned food and from washing powder to ice cream. The original MWPC positron camera performed reliably for over 15 years. During this period, the use of PET in medicine became more widespread, and equipment manufacturers 34 developed a variety of off-the-shelf PET detector systems, including gamma camera PET systems that were marketed as multipurpose imaging systems for nuclear medicine. In 1999 we replaced the MWPC camera with one of these systems, comprising a pair of gamma camera heads operating in coincidence. Each head consists of a sheet of sodium iodide scintillator backed by an array of 55 photomultiplier tubes (PMTs) that detect the flash of light produced by a g-ray interacting in the scintillator and localize this to within a few mm. This system is ideal for PEPT, with an open geometry able to accommodate large rigs (Figure 3). It can record up to 100 k g-ray pairs per second, compared to a maximum of 5 k per second from the MWPC system. Dedicated medical PET scanners generally use a different approach, comprising hundreds of small, highefficiency detectors, mounted in rings about the patient. Such scanners offer significantly higher sensitivity and count rate than a gamma-camera PET system, but the restricted field of view is unsuitable for studying large engineering rigs. Fortuitously, in the last Nuclear Physics News, Vol. 18, No. 4, 2008 few years the world of medical PET has been revolutionized by the introduction of combined PET/CT scanners, in which a near-simultaneous Xray image of a patient’s anatomy can be measured and superimposed on the functional PET image. As a result, a number of older PET centers decided to replace their existing PET scanners with PET/CT systems, and Birmingham was able to acquire their old scanners. Like this, we have recently obtained four complete PET scanners as well as components from two others, and have reconfigured them for our use. The detectors inside these scanners are grouped in modules, each with its own electronics. A typical scanner contains 32 such modules. A flexible PEPT system can be constructed simply by arranging the modules in a different geometry. Whereas for PET it is important to sample g-rays uniformly around a complete circle, for PEPT Figure 3. The gamma-camera system being used in a PEPT study of a fluidized bed. impact and applications any arrangement of detectors can be used provided the tracer is always in line between at least one pair. The resulting “modular positron camera” has the advantage that it is transportable, so that PEPT studies can be performed outside the lab. In the last two years, this system has been used for several applications, including observing single particle motion inside a large fluidised bed at BP’s Hull site (230 km from Birmingham) and studying the casting of liquid aluminium into molds in the University Foundry (Figure 4). When the detector modules are packed closely together this system can detect up to 4 M g-ray pairs per second, allowing very accurate tracking of fast-moving tracers. Not all the work at Birmingham uses PEPT. Conventional PET has recently been used to study the blending of powders for pharmaceutical formulation. Because each PET scan takes several minutes, this study was carried out in stop/start mode: a small amount of labeled powder was added to the mix and imaged, the blender was run for a few seconds and then stopped for another image, and so on. PET is especially suited for observing very slow flows, and over the years we have performed a number of studies on flow of liquid or gas through geological samples. Using components from one of the medical scanners, we have also built what we believe to be the world’s largest PET scanner: a ring of 128 detector blocks with an inner diameter of 2.3 m. Positron emitting isotopes are generally produced using a cyclotron. Birmingham has a long history of developing and operating cyclotrons, beginning with the Nuffield Cyclotron, which operated from 1948 until 1999. The PET work was started with the aid of radioisotopes produced by Figure 4. The modular positron camera being used in a PEPT study of liquid aluminium casting. The detector modules are mounted inside protective boxes and arranged in four orthogonal stacks. the Radial Ridge Cyclotron, which commenced operating in 1960, but by the late 1990s this cyclotron was becoming increasingly unreliable, and the opportunity was taken to replace it with a more modern cyclotron. The present Scanditronix MC40 Cyclotron was purchased second-hand from the VA Medical Center, Minneapolis, at the beginning of 2002, was moved to Birmingham and recommissioned during 2002–2004, and has been fully operational since March 2004. During 2005, we extended the layout by acquiring the switching magnet from the former Vivitron accelerator, which allows the beam to be switched between 12 independent target stations. The MC40 is a flexible research cyclotron, delivering variable energy beams of hydrogen and helium ions with maximum energies of 40 MeV (protons or alphas), 20 MeV (deuterons), and 53 MeV (3He). It has proved extremely reliable, and in addition to producing the tracers required by the Positron Imaging Centre it is used for a variety of research purposes, including surface activation of components for wear testing, and measuring radiation effects on electronics destined for use in space. The MC40 cyclotron also produces 81Rb daily for sale to hospitals across the United Kingdom. The activity required in a PEPT tracer depends on the tracer speed, the size of the system (detector separation), and the extent of g-ray attenuation in surrounding material. In a compact low-mass system accurate high speed tracking can be achieved using a tracer with an activity of around 10 MBq, but for a large dense Vol. 18, No. 4, 2008, Nuclear Physics News 35 impact and applications system (e.g., a stirred water tank) activities up to 40 MBq are optimal. Just as in medical PET, most studies at Birmingham use the radioisotope 18F, which has a half-life of 110 minutes, but whereas medical PET centers generally produce 18F by proton irradiation of water, which is isotopically enriched in 18O, at Birmingham the alternative production route using 3He on natural oxygen is used. In this way, everyday materials such as glass or alumina beads can be directly activated for use as PEPT tracer particles. Targets containing oxygen are irradiated with a 36 MeV 3He beam, producing 18F through the reactions 16O(3He, p)18F and 16O(3He, n)18Ne ⇒18F. In many cases, the target is water (natural water, not H218O) so that the result is a very dilute solution of radioactive fluoride, which must then be attached to the particle of interest. A range of 36 techniques has been developed for labeling particles including polymers, plant seeds, catalysts, minerals, coal, metals, and microcrystalline cellulose down to 100 mm in size. Tracer particles produced in this way survive well in dry conditions or in organic solvents, but in an aqueous environment the activity tends to leach away rapidly. A crude solution to this problem is obtained by painting the surface of the tracer after labeling, thus sealing the activity inside. A better approach is to use a cationic radionuclide such as 61Cu (half-life 3.4 hours) or 66Ga (9.3 hours), which binds more irreversibly to particle surfaces. Looking ahead, we consider that PET and PEPT may be of value in numerous untried fields. It’s surprising what can be achieved using second-hand equipment (cyclotron and PET scanners)! Nuclear Physics News, Vol. 18, No. 4, 2008 Acknowledgments I thank all the colleagues who have worked with me on these projects over the years, in particular Xianfeng Fan, Andy Ingram, and Jonathan Seville, and I acknowledge with gratitude the continuing financial support from EPSRC. DAVID PARKER Positron Imaging Centre, School of Physics and Astronomy University of Birmingham meeting reports The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13 The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics, called CGS13 for short, was held from Monday, August 25 to Friday, August 29 at the Institute of Nuclear Physics of the Universität zu Köln, with Prof. J. Jolie as the chairman. This conference, of rather wide scope, already has a longstanding tradition, going to 1969, when the first edition was organized at Studsvik, Sweden, starting in Petten (the Netherlands) in 1974, Brookhaven (USA) in 1978, Grenoble (France) in 1981, coming into a 3-year cycle since then. The places the meeting was held onward were Knoxville (USA) in 1984, Leuven (Belgium) in 1987, Asilomar (USA) in 1990, Fribourg (Switzerland) in 1993, Budapest (Hungary) in 1996, Santa Fe (USA) in 1999, Prague (Czech Republic) in 2002, and Notre-Dame (USA) in 2005. The tradition of alternating on both sides of the Atlantic Ocean, with a 3-year interval, will continue also this time. At the special lunch meeting of the Advisory and Program Board, an unanimous decision was made to have the next meeting in the series, that is, CGS14, at the University of Guelph, moving to Canada for the first time. The organization will be taken up by Prof. P. Garrett and a local organizing team. The series of CGS conferences is characterized by a broad range of topics encompassing Nuclear Structure, covering most recent developments in both experimental and theoretical research. Many talks showed the presence of a strong synergy of recent experiments in various fields of nuclear physics with recent advances in state-of-the-art shell-model methods, nuclear meanfield and beyond approaches also invoking the importance of symmetry concepts as a guiding principle to understand the atomic nucleus. Nuclear Reactions including the study of statistical properties of nuclei formed a recurring theme in the present edition of CGS13. Traditionally, Nuclear Astrophysics takes a particularly strong position in the series of meetings and this was again so in Köln, strongly emphasizing recent experimental work and pointing toward the need of the best possible input from theorists and new theoretical developments. Time has also been devoted to have a couple of sessions on Nuclear Data. The conference always has been the place where much attention and interest is given to new experimental techniques and facilities, covering a whole range from new detector systems, development of new radioactive beams, over the use of neutrons (cold neutron beams, neutron sources). Also, sessions on practical applications (covering material science, imaging, interface with other scientific disciplines such as chemistry, biology, . .) were included at the CGS13 conference. A particularly attractive part comes from the fact that neutrons can play a very important and fundamental role in the study of basic physics. The session on Fundamental Physics took up that line of research and exciting new results were presented. The conference in Köln was a very lively example of presentations, discussions covering the overlapping regions between various exciting domains in the physics of atomic nuclei, and their study through the use of a large set of complementary probes. Due to the large number of participants (164 registered physicists representing 28 different countries) and the many high-quality abstracts submitted, on Tuesday, Wednesday, and Thursday morning, parallel sessions had to be organized next to the 16 plenary sessions. With the two lecture rooms very close to each other, the movement from one to the other went rather smoothly. Among the participants, there was a very large fraction of young graduate, postdoc, and junior staff people present. At the same time, it is good to mention that Till von Egidy of the Technische Universität Münich was the one physicist present who attended all 13 editions of the CGS conference. The program was densely packed and thus the conference trip on Wednesday afternoon was very much welcome. The trip went first by bus to the beautiful city of Linz, south of Köln, where a guided tour passed through the narrow alleys of this medieval little town. The way back went relaxingly and with fine weather by boat on the river Rhine, passing through the beautiful region near Bad Honnef and Köningswinter (close to the “Siebengebirge“). The early night was coming with the boat arriving near to the illuminated Dom in the heart of Köln. Vol. 18, No. 4, 2008, Nuclear Physics News 37 meeting reports A poster session was organized in the late afternoon on Tuesday. This poster session sought the very best poster(s) presented by graduate students and postdoctoral fellows with an award of 500 Euro. The best poster for the ”the Founder’s Award,” an award that was inaugurated in honor of the memories of the late Jean Kern, Subramanian Raman, and Gabor Molnar, all of whom played a major role in establishing thrust and growth of the early meetings into a major international conference, had to be selected among a large number of highquality contributions. The selection committee— H.Börner (ILL Grenoble), F. Käppeler (Forschungszentrum Karlsruhe), and K. Heyde (Univ.Ghent)—ended up splitting the prize among two very fine contributions. One half went to a starting graduate student from the University of Köln, Linus Bettermann, with a poster on mixedsymmetry states. The other half was given to Steven Pain, a postdoctoral fellow working at Oak-Ridge National Laboratory (ORNL), with a contribution on the development of the ORRUBA Silicon Detector Array. A memorable event was the conference dinner, on Thursday evening, held at the “Imhoff Schokoladenmuseum.” This event gave rise to the possibility of socializing in a relaxed atmosphere among the many participants, and this over a great buffet and fine wines from the Baden region (Kaiserstuhl). The local organizing team is to be congratulated for the impeccable organization of this 13th edition of the conference: not only was a scientific program of very high quality arranged, but the flow throughout the five-day conference ran smoothly indeed in the spacious Physics building, with ample room for computing, having discussions, and taking time at coffee breaks with cake and cookies. CGS13 will definitely go into history as a worthy partner of this gallery of conferences. KRIS HEYDE Department of Subatomic and Radiation Physics University of Ghent(Belgium) Hadron Physics Summer School 2008 More than 80 graduate and advanced undergraduate students from 14 countries and 4 continents participated in the Hadron Physics Summer School HPSS2008 held at Physikzentrum Bad Honnef, Germany, August 11–15, 2008 (Figure 1). Similar to the preceding COSY Summer School (CSS) 2002, 2004, and 2006, this school consisted of lectures and working groups on theoretical, experimental, and accelerator aspects. The focus was on current issues in hadron physics with emphasis on the latest programs at the accelerators COSY (Jülich) and ELSA (Bonn), also featuring future FAIR projects like HESR/PANDA and PAX. During the very successful school, the students were given a guided tour to the Cooler Synchrotron COSY at Jülich Forschungszentrum. 38 The HPSS2008 was jointly organized by scientists working at the Nuclear Physics Institute (http://www. fz-juelich.de/ikp) of the Jülich Center for Hadron Physics at Jülich Forschungszentrum and by the DFG Transregio TR 16 (Subnuclear Structure of Matter, http://sfb-tr16. physik.uni-bonn.de/) of the Universities Bonn, Bochum, and Giessen. In addition, the HPSS2008 was sponsored by DAAD (German Academic Exchange Service) and DPG (Deutsche Physikalische Gesellschaft), making the participation of young motivated students into this challenging enterprise possible. Figure 1. Participants of HPSS2008 in front of Physikzentrum Bad Honnef. Nuclear Physics News, Vol. 18, No. 4, 2008 meeting reports It is intended to conduct the HPSS every second year. The series will be supplemented by lecture weeks in the alternate years, which will consist of invited lectures and student contributions. The lecture weeks are self- contained and will also be an excellent opportunity for graduate students and early post-graduates to deepen the knowledge gained at HPSS. For more detailed information, see:\\http://www.fz-juelich.de/ikp/ hpss2008/. FRANK GOLDENBAUM FZ Jülich Vol. 18, No. 4, 2008, Nuclear Physics News 39 news and views BEPC-II/BES-III Complex On late Saturday afternoon July 19, researchers at the Chinese Academy of Science’s Institute of High Energy Physics in Beijing produced for the first time collisions in the upgraded BEPC-II electron positron collider that were observed in its brand new associated detector, called BES-III. Although BEPC-II and BES-III had already been carefully tested separately, this was the first time they operated together. These first collisions represent a major milestone of this project, which involved eight years of planning and construction. When it is fully operational, the BEPC-II/BES-III complex will be the world’s premier facility for studying the properties of particles that contain a charmed quark (c-quark), the fourth of an assortment of six different quarks that physicists have identified as the most fundamental building blocks of matter. In BEPC-II, c-quarks, which have a mass that is about 3,000 times that of the electron, are produced together with their equal-mass antimatter counterpart, anti-charmed quarks (c-quarks), in head-on collisions of high energy electrons and anti-electrons (familiarly known as positrons). In these collisions, the electron and positron annihilate each other and in the process their energy is converted into the massive c- and c-quark pair in accordance with Einstein’s famous relation E = mc2. To accomplish this, the BEPC-II team confines a tightly bunched cluster of approximately 50 billion electrons inside a vacuum tube that threads through a ring of powerful electro-magnets that maintains the electron bunch in a nearly circular orbit. Likewise a similar “bunch” of positrons is made to counter-rotate in an identical second ring of magnets. Figure 1. The BESIII detector in the interaction region of BEPCII. 40 Nuclear Physics News, Vol. 18, No. 4, 2008 The two bunches, which have a vertical profile of only about five millionths of a meter, are made to cross each other in the center of the BES-III detector. Occasionally, an electron in one bunch hits a positron in the other bunch head-on and the two particles annihilate each other to produce a pair of particles: one containing a c-quark and an associated one that contains a c-quark. These so-called charmed particles rapidly decay into more conventional particles like p- and K-mesons whose energies and velocities are precisely measured in the BES-III spectrometer. From these measurements, the properties of the parent charmed particles can be deduced. BEPC-II is a major upgrade of IHEP’s previous collider BEPC. The major change has been the addition of a second ring of magnets that allows the electron and positron beams to be stored separately. In BEPC, the electrons and positrons shared the same vacuum tube in a single ring of magnets, and this arrangement could accommodate only a single bunch each of electrons and positrons, thereby limiting the rate at which interesting particles are produced. The two separate rings of BEPC-II will allow for 93 bunches in each ring. In addition, BEPC-II has many other improvements including a more powerful injection accelerator that produces the high energy electrons and positrons, and an extensive use of superconducting technology, both for the acceleration and magnetic focusing of the stored electron and positron beams. The net effect of all of these improvements will be a more than hundred-fold increase in the collision rate. news and views Figure 2. The first charmed-meson pair event seen in BES-III. The BES-III detector is completely new with a number of major improvements over its predecessor, BES-II. These include its huge superconducting magnet, which produces a magnetic field throughout the detector that is about 20,000 times stronger than the Earth’s magnetic field. This strong magnetic field deflects charged particles as they traverse the detector and by measuring the amount of deflection researchers can make precision measurements of the particles’ velocities. This magnet, which is the most powerful magnet in China, was built at IHEP by the laboratory’s research staff. In addition, BES-III contains a large array of 6,240 crystals of Cesium Iodide that are used to measure the energies of the high-energy gamma rays that are produced in the collisions. The combination of the superconducting magnet and the large crystal array enables the BES-III detector to measure the energies and velocities of the produced particles with more than ten times better precision than was previously possible with BES-II. To handle the huge data rates expected in the BES-III detector, a specialized state-of-the-art high-speed data communication system has been developed and implemented. BEPC-II’s double ring system was completed in October 2006, beams were first stored during the following month and first collisions were produced in March 2007. The assembly of the BES-III detector was completed in January of this year, and it was moved into the interaction region in early April (see Figure 1). In last weekend’s initial test run, a pair of charmed particles, where one contains a c-quark and the other a c-quark, was recorded in the detector approximately every ten minutes. A display of one of the first such events is shown in Figure 2. The collision rate in the initial test run was about a factor of 4,000 times slower that the project’s ultimate design goal of 6 or 7 charmed-particle pairs per second. This lower rate was partly because the researchers purposely limited the intensity of the electron and positron beams in order to avoid possible damage to the very sensitive detection sensors of the BES-III spectrometer while they made sure that everything is working as expected. The next day, intensities were increased and a tentimes higher collision rate was measured. Over the next several weeks the intensity of the beams will gradually be further increased while at the same time BES-III’s nearly 20,000 detection elements will be carefully adjusted and calibrated. When this process is completed, sometime in the early Fall, the BES-III research program will begin. Recently, researchers working at IHEP and at laboratories in Japan and the United States have observed a number of interesting and unexpected properties of charmed particles that will be investigated with unique sensitivity with BES-III; these observations have added substantially to the worldwide particle physics community’s interest in the BES-III research program. These new developments include the surprising observation that neutral charmed mesons, that is, mesons containing a c-quark and an anti-up quark (u-quark), spontaneously transform into anti-charmed mesons (i.e., u- and c-quark mesons) and vice versa, a phenomenon that was quite unexpected. BES-III will be uniquely able to perform important measurements that categorize this process to help theoretical physicists Vol. 18, No. 4, 2008, Nuclear Physics News 41 news and views understand the root cause for these transformations. Recently, there have been hints that inside so-called Ds mesons, which are particles comprised of a c-quark and an anti-strange quark (s-quark), the constituent c- and s-quarks annihilate each other at a rate that seems to be higher than that predicted by theory. If this discrepancy could be unequivocally established, which is something that BES-III is particularly well suited to do, this would be striking evidence for a whole new regime of forces and asso- ciated particles in nature. In addition, the BES-II experiment at IHEP and a number of experiments at other laboratories have uncovered a new class of particles that do not fit into the conventional quark model scheme. To date, in spite of considerable effort, theorists have been unable to achieve a compelling picture that describes these states. More detailed measurements are necessary, and this is something that BES-III will do. It is estimated that these and the many other topics to be investigated by BES-III correspond to an approximately ten-year-long program of intensive research. This research will be carried out by an international team of researchers from China, Hong Kong, Germany, Japan, Russia, and the United States. The observation of first collisions in the BEPC-II/BES-III facility was an important milestone in this research program. ULRICH WIEDNER Bochum Path for Mass Mapping of Superheavies is Open It happened that just on August 8, 2008 (on the distinguished day of 08.08.08!) the SHIPTRAP collaboration at GSI succeeded in directly measuring the masses of three nobelium isotopes. Never before have mass values of any isotope of the trans-uranium, or even trans-fermium elements of the Periodic Table been directly determined. Since the idea of the existence of an island of superheavy nuclides was put forward about forty years ago, heroic attempts have been undertaken to reach this alluring site in the sea of nuclear instability. Stepby-step discoveries of new superheavy elements, performed over the last decades at GSI (Darmstadt) and at JINR (Dubna), paved the way toward this mysterious island. Being landed, we still do not know too much on its extension on the chart of the nuclides. The masses, that is, the total binding energies, allow us to explore the landscape of the predicted island and to shed light on the structure and the stabilizing shell effects of superheavies providing information complementary 42 to nuclear decay spectroscopy investigations that are feasible in this region. As the isotopes of new elements have been identified by their a-decay, it was previously thought that about a dozenlong a-chains, which originate from superheavy nuclides and end in the region of well-known masses, can help to determine, although indirectly, the mass values of superheavies. However, the attempts to complete this goal by searching for some unknown a-emitters in the long chains were unsuccessful so far because of very small a-decay probabilities. Thus, direct mass measurements of superheavies became the only, but challenging, option left. About ten years ago, H.-Jürgen Kluge came up with the idea to install a Penning trap system behind the velocity filter SHIP at GSI in order to enable this kind of direct measurement for rare isotopes produced in fusion-evaporation reactions at SHIP, utilizing the intense primary beam provided by the heavy-ion accelerator UNILAC. Nuclear Physics News, Vol. 18, No. 4, 2008 Penning traps are nowadays powerful tools for mass measurements of exotic short-lived nuclides. The main Penning trap techniques used at the SHIPTRAP-facility are very similar to those pioneered by ISOLTRAP at ISOLDE/CERN. SHIPTRAP, however, utilizes exotic radionuclides from heavy-ion fusion reactions after inflight separation at SHIP, which are stopped in a gas cell, then extracted, cooled, and bunched with subsequent Figure 1. Time-of-flight cyclotron resonance for doubly charged 253No-ions. news and views this limit will be pushed further down: It is planned to install a cryogenic gasstopping cell and to introduce a nondestructive detection technique where a mass value can be obtained using only one single ion for a mass determination. This activity is underway in collaboration with groups from GSI, MaxPlanck Institute for Nuclear Physics in Heidelberg, from different universities such as University of Mainz, München, and Giessen, as well as from the St. Petersburg Nuclear Physics Institute. Figure 2. Alpha-decay chains starting from darmstadtium isotopes and passing the directly mass-measured nobelium nuclides. injection into a double Penning-trap system. After the isobar selection in the first trap, the mass of a charged particle is determined from its cyclotron frequency, which is measured by a time-of-flight ion-cyclotron resonance technique. With this method one can determine the mass value precisely. The accuracy of Penning trap mass spectrometers achievable for radioisotopes, which is typically about 10−8 (corresponding to 1 keV in the region of A ≈ 100) is superior to all other methods. A great advantage of SHIPTRAP is its exceptional capability to measure directly the masses of trans-uranium nuclides toward superheavies. During the last experimental run in August 2008 the masses of three nobelium isotopes (Z = 102) with mass numbers A = 252, 253, and 254 were measured at SHIPTRAP. A time-of-flight resonance curve for 253 No is shown in Figure 1. It allows determining the so far unknown mass value for this nuclide on a level of a few times 10−8 accuracy. The position of the measured nobelium isotopes in the a-decay chains is shown in Figure 2. As can be seen from this figure the mass values up to 269Ds and 270Ds (Z=110) are linked via alphachains and can now be connected to the directly determined nobelium mass values. Notable information about the structure of superheavies can be derived from masses of different nobelium isotopes, which have a neutron number around the semi-magic N=152. Just this number of neutrons luckily constitutes the nuclide 254 No whose total binding energy was measured directly at the SHIPTRAP. As a consequence of this pioneering experiment the door for a mass mapping in the region of superheavy elements is open. At present, nuclides with production cross-sections on the level of 500 nbarn are accessible for direct mass measurements with SHIPTRAP. With planned improvements of the system MICHAEL BLOCK GSI, Darmstadt YURI NOVIKOV PNPI, St. Petersburg Vol. 18, No. 4, 2008, Nuclear Physics News 43 news and views IBA-Europhysics Prize 2009 for Applied Nuclear Science and Nuclear Methods in Medicine Call for Nominations The Nuclear Physics Board of the EPS calls for nominations of the 2009 IBA-Europhysics prize. The award will be made to one or several individuals for outstanding contributions to Applied Nuclear Science and Nuclear Methods and Nuclear Researches in Medicine. The Board would welcome proposals that represent the breadth and strength of Applied Nuclear Science and Nuclear Methods in Medicine in Europe. Nominations should be accompanied by a completed nomination form, a brief curriculum vitae of the nominee(s), and a list of major publications. Letters of support from authorities in the field that outline the importance of the work would also be helpful. Nominations will be treated in confidence and although they will be acknowledged there will be no further communication. Nominations should be sent to: Selection Committee IBA Prize, Chairman Prof. G. Viesti, Dipartimento di Fisica,, Galileo Galilei,“ Università di Padova, Via Marzolo 8, I-35131 Padova, Italy. Phone/Fax: +32 049-8277124. E-mail: [email protected] or giuseppe. [email protected] For nomination forms and more detailed information see: the website of the Nuclear Physics Division, http:/ 63 /ific.uv.es/epsnpb/ and the website of EPS, www.eps.org (EPS Prizes, IBAEurophysics Prize). The deadline for the submission of the proposals is January 15, 2009. Sponsored by Ion Beam Applications, Belgium. General Description The European Physical Society (EPS), through its Nuclear Physics Board (NPB), shall award a Prize to one or more researchers who have made outstanding contributions to Applied Nuclear Science and Nuclear Methods and Nuclear Researches in Medicine (investigation, aid to diagnosis, and/or therapy). Such contributions shall represent the breadth and strength of Applied Nuclear Science and Nuclear Methods in Medicine in Europe. Prize Rules 1. The Prize shall be awarded every two years. 2. The Prize shall consist of a Diploma of the EPS and a sum of 5000 € (to be shared, in case of more than one laureate). 3. The money of the prize is provided by the Belgian Company IBA (Ion Beam Applications). Nuclear Physics News, Vol. 18, No. 4, 2008 4. The Prize shall be awarded to one or more researchers. 5. The Prize shall be awarded without restrictions of nationality, sex, race, or religion. 6. Only work that has been published in refereed journals can be considered in the proposals for candidates to the prize. 7. The NPB shall request nominations to the Prize from experts in Nuclear Science and related fields who are not members of the Board. Call for nomination will be published in Europhysics News, Nuclear Physics News International, and at the homepage of the IOP journal “Physics in Medicine and Biology.” 8. Self-nominations for the award shall not be accepted. 9. Nominations shall be reviewed by a Prize Committee appointed by the NPB. The Committee shall consider each of the eligible nominations and shall make recommendations to the NPB, taking also into account reports of referees who are not members of the Board. 10. The final recommendation of the NPB and a report shall be submitted for ratification to the Executive Committee of the EPS. GIUSEPPE VIESTI Padova, Italy calendar 2009 January 12–16 Stellenbosch, South Africa. Lasers and Accelerators http://academic.sun.ac.za/lasers& accelerators/ January 19–28 Stellenbosch, South Africa. 20th Chris Engelbrecht Summer School in Theoretical Physics http://academic.sun.ac.za/summerschool/ 2009.html January 26–30 Bormio, Italy. XLVII International Winter Meeting on Nuclear Physics http://panda.physik.uni-giessen.do:8080/ indics/conferenceDisplay.py?confId=7 March 16–20 Bochum, Germany. European Nuclear Physics Conference http://www.epl.rub.de/EUNPC March 21–24 Prague, Czech Republic. International Conference on Compating in High Energy and Nuclear Physics CHEP’ 09 http://www.particle.cZ/conferences/ chep2009/ March 29–April 4 Knoxville, Tennesse, USA. Quark Matter 2009 http://www.phy.ornl.gov/QM09 March 30–April 1 Pisa, Italy. EURISOL Design Study Town Meeting http://www.eurisol.org/site01/town_ meeting-t-202.html April 24–May 1 Erice, Sicily, Italy. Workshop on Hadron Beam Therapy of Cancer http://erice2009.na.infn.it/ May 4–8 Dubrovnik, Croatia, Nuclear Structure and Dynamics http://www.phy.hr/~dubrovnik09/ May 4–8 Vienna, Austria. International Topical Meetingon Nuclear Research Applications and Utilization of Accelorators (AccApp’09) http://www-pub.iaea.org/MTCD/Meetings/ Announcements.asp?confId=173 May 13–16 Chateau de Cadarache, France International Workshop on Nuclear Fission and Fission-Product Spectroscopy hhttp://www.fission2009.com/ June 2–5 Mackinac Island, Michigan, USA 3rd International Conference on “Collective Motion in Nuclei under Extreme Conditions” (COMEX 3) http://meetings.nscl.msu.edu/COMEX3/ June 15–17 Bad Honnef, Germany. Precision Experiments of Lowest Energies for Fundamental Tasts and Constants http://www.mpi-nd.mpg.de/blaum/events/ heraeus09/ June 21–26 New London, NH, USA Gordon Conference on Nuclear Chemistry (Nuclear Structure) http://www.grc.org/programs.aspx? year=2009&program=nuchem June 30–July 4 Dubna, Russia. Nuclear Structure and Related Topics http://theor.jinr.ru/~nsrt/2009/ September 27–October 3 Milos, Greece 8th European Research Conference on “Electromagnetic Interactions with Nucleons and Nuclei” (EINN 2009) http://www.iasa.gr/EINN_2009/ September 28–October 2 Sochi, Russia International Symposium on Exotic Nuclei EXON 2009 http://exon2009.jinr.ru/ November 29–December 4 Napa, California, USA. 4th AsiaPacific Symposium on Radiochemistry (APSORC’09) http://apsore2009.Berkeley.edu/ 2010 July 19–23 Heidelberg, Germany. Nuclei in the Cosmos NIC XI http://www./sw.uni-heidelberg.de/nic2010 More information available under: http://www.nupecc.org/calendar.html . . . and check also http://www.ect.itÞMEETINGS 44 Nuclear Physics News, Vol. 18, No. 4, 2008