- Email: [email protected]
Status of the EURISOL project
Nuclear Instruments and Methods in Physics Research B 204 (2003) 759–764 www.elsevier.com/locate/nimb
Status of the EURISOL project Jean Vervier
*
Institut de Physique Nucl eaire, Chemin de Cyclotron 2, Universit e Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
Abstract EURISOL is a preliminary design study of the European next-generation isotope separation on line (ISOL) radioactive nuclear beam (RNB) facility, which should extend and amplify, beyond 2010, the exciting work presently carried out with the first-generation ISOL/RNB facilities in Europe and all around the world. The present paper presents a status report, as to 1 May 2002, on the various tasks identified within the project. 2003 Elsevier Science B.V. All rights reserved. PACS: 20.29.90.+r
1. Introduction In 1999, the OECD Megascience Forum Working Group on Nuclear Physics, which included representatives from OECD Member countries all around the world, issued a Report [1], with a Section on radioactive nuclear beam (RNB) facilities. This Section includes the following recommendation: ‘‘The Working Group recognises the importance of RNB facilities for a broad programme of research in fundamental nuclear physics and astrophysics, as well as applications of nuclear science. A new generation of high-intensity RNB facilities of each of the two basic types, ISOL and In-Flight, should be built on a regional basis. Interested governments are encouraged to undertake the necessary decisions within the next few years, and the facilities themselves should become operational in 5–10 years’’. This 1999 recommendation is progressively coming into practice, as shown by the many *
Tel.: +32-10-416596; fax: +32-10-452183. E-mail address: [email protected] (J. Vervier).
projects of next-generation RNB facilities discussed during the present EMIS-14 Conference. In North-America, ISAC-1 started operation at TRIUMF, Vancouver, Canada, and ISAC-2 has been approved [2,3]. In the United States, progresses have been made at the In-Flight facility of the National Superconducting Cyclotron Laboratory [4]; the Rare Isotope Accelerator RIA project has been elaborated, R and D on some of its critical components has started and the project includes an In-Flight component [5,6]. At RIKEN, Japan, a next-generation In-Flight facility is under construction [7,8]. In Europe, a major upgrade of the In-Flight facility at the GSI, Darmstadt, Germany is proposed [9,10]. Against this background, the EURISOL project, supported by the European Commission, aims at a preliminary design study of the next-generation European ISOL/RNB facility which should extend and amplify, beyond 2010, the exciting work presently carried out with the first-generation ISOL/RNB facilities, operating or under construction, in Europe and all around the world, as illustrated in many talks during the present EMIS-14 Conference.
0168-583X/03/$ - see front matter 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(03)00499-3
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The EURISOL project associates ten European Nuclear Physics laboratories, i.e.: GANIL, Caen, France; the Chalmers University of Technology (CUT), G€ oteborg, Sweden; the Katholieke Universiteit Leuven (KULeuven), Leuven, Belgium; GSI, Darmstadt, Germany; the Instituto Nazionale di Fisica Nucleare (INFN), Roma, Italy (and in particular, the Laboratori Nazionale di Legnaro, Padova, Italy); the Institut de Physique Nucleaire (IPNO), Orsay, France; the CEA/DAPNIA, Saclay, France; ISOLDE/CERN, Geneve, Switzerland; the Accelerator Laboratory (JYFL), Jyv€ askyl€ a, Finland; the Rutherford-Appleton Laboratory (RAL), Didcot, United Kingdom. The Project started on January 1, 2000 and should conclude its work by December 31, 2003. It is a preliminary design study (phase 1), which should be followed by RTD programmes, starting in 2002 and lasting 4–5 years (phase 2), and by a full engineering design of the proposed facility, leading, hopefully, to its commissioning around the year 2010 (phase 3). The following tasks have been identified for the EURISOL programme: • The identification of key experiments to be performed with the proposed facility, and the definition of their requirements, in terms of the types, energies and intensities of the needed RNBsÕ. This task is coordinated by CUT (Bjorn Jonson). • The definition of the driver accelerator, which will produce the radioactive nuclei. This task is coordinated by IPNO (Alex Mueller). • The investigation of the target–ion source assembly, wherein the radioactive nuclei will be produced and ionized. This task is coordinated by ISOLDE/CERN (Helge Ravn). • The definition of the mass-selection system and post-accelerator, which will select the radioactive ions according to their masses and bring them to the desired energies. This task is coordinated by GANIL (Eric Baron and MarieHelene Moscatello). • The identification of the scientific instrumentation to be used near the planned facility, to perform, in particular, the key experiments. This € yst€ task is coordinated by JYFL Juha A o.
• The elaboration of the cost estimates of the proposed facility, construction and running costs, hopefully at the 20% level, and of the final report of the project. This will be carried out by all the participants to the EURISOL project, in particular the Scientific Coordinator (Jean Vervier) and the Technical Coordinator (John Cornell). Within the various tasks just listed, special attention has been paid to the following three points: • The identification of the RTD programmes, on crucial technical points related to the proposed facility, which will have to be carried out in phase 2 of the project (see above) before the full engineering design of phase 3. • The identification of synergies between the proposed facility and other major European projects or laboratories. These projects include: the European spallation source (ESS); the transmutation of nuclear wastes (TNW); the neutrino factory within the High Energy Physics programmes, . . . • The study should, in a first phase, be site independent. In the present paper, we successively present: the main options which have been taken for the proposed EURISOL project; the progresses made in the various tasks identified above; the future perspectives of the project during the next few years.
2. Main options for the EURISOL project There are many different ways to produce RNBsÕ by the ISOL method, depending on the type and energy of the projectiles produced by the driver, on the target and ion source, and on the energy of the post-accelerator. In order to guide the work of the various groups in charge of the tasks defined in Section 1, the Steering Committee of the EURISOL project, which includes representatives of the 10 laboratories associated to the project and the coordinators of the task groups, has taken the following main options:
J. Vervier / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 759–764
• The widest scientific field wherein key experiments are likely to be performed lies in the neutron-rich region of the periodic table, although the proton-rich region should not be neglected. This means that fission will be an important mode of production of the radioactive nuclei, together with spallation. • The driver accelerator should produce protons, at energies around 1 GeV, with very high intensities, in the several mA range, i.e. with very high beam powers, around 5 MW. Such beams will be used in two ways: either, by sending the full beam power on a suitable target, to produce very high fluxes of fast neutrons, which will in turn induce fission in a uranium target, yielding at least 1015 fissions per second, i.e. very large quantities of neutron-rich radioactive nuclei (this is the so-called indirect method [11]); or by sending a fraction of the beam intensity, at least 100 lA, directly on a spallation target, producing thereby mostly proton-rich nuclei. The performances of the driver for accelerating other particles than protons, with a mass-tocharge ratio of 2, should be studied, and the possibility of using, as driver, a high-energy (50–70 MeV), high-intensity (20–30 mA) electron accelerator (which could induce photofission in a secondary uranium target through the bremsstrahlung of the electron beam in a primary target) should be investigated. • Various types for the target–ion source assembly should therefore be investigated: a very high-power neutron-producing target; a fission target for at least 1015 fissions per sec; a spallation target for at least 100 lA of 1 GeV protons; and the associated ion sources. Special attention should be paid to the efficiencies of these various components, in particular to the minimization of the losses due to the delay times involved in the diffusion and effusion processes out of the target and towards the ion source, and to the chemical selectivity during these processes. • The mass-selection system and post-accelerator should select the ions according to their masses, hopefully separating isobars, and produce RNBsÕ in three different energy regions: (i) at very low energies (tens of keV), for ‘‘ISOLDE’’ types of experiments; (ii) at intermediate ener-
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gies, up to about 10 MeV per nucleon, for fusion–evaporation reactions, Coulomb excitation, transfer reactions, nuclear astrophysics experiments, . . .; (iii) at high energies, up to 100 MeV per nucleon up to A 100, for fragmenting RNBsÕ, investigating the nuclear equation of state (EOS), . . . • The scientific instrumentation should be adapted to the proposed key experiments and to the planned energies of the RNBsÕ. These options have been presented, and discussed, to the European scientific community on Nuclear Structure at the occasion of two Town Meetings, at Orsay, France, on 6–7 November 2000 and Abano Terme, Italy, on 24–25 January 2002, where the partial results already obtained were also reviewed.
3. Progresses in the various tasks of EURISOL 3.1. Key experiments There are, by now, several detailed Reports on the various topics in Nuclear Physics, Nuclear Astrophysics, Fundamental Interactions and Applications of Nuclear Science which will be addressed by the next-generation RNB facilities, ISOL and In-Flight. The key experiments task group concentrated on some of these topics: (1) nuclear structure far from stability, i.e. the position of the proton and neutron driplines, radioactive decays far from stability, changes in the shell structures, halo nuclei, heavy and superheavy nuclei; (2) nuclear reactions with RNBsÕ, mostly one-, two- and multiple-nucleon transfers; (3) high-spin physics in exotic nuclei; (4) the nuclear EOS for different isospins; (5) nuclear astrophysics; (6) tests of the Standard Model and of fundamental conservation laws. One of the topics examined by the key experiments task group was the production of very exotic neutron-rich nuclei by fragmenting very high fluxes (e.g. 1011 particles per second) of neutronrich RNBsÕ post-accelerated to energies around 100 MeV per nucleon. The first calculations [12] were carried out using the modified EPAX formula
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[13]. A further investigation, by the group of Karl– Heinz Schmidt at GSI [14], used more sophisticated and hopefully more physical codes, based on the abrasion–ablation model, i.e. ABRABLA [15], which uses a Monte Carlo simulation, and COFRA [16], a simplified, analytical version of ABRABLA. The comparison of these codes [13,16] between themselves and with the experimental data shows that the EPAX formula is reasonably successful for predicting the fragmentation of stable projectiles, but overestimates the cross-sections for neutron-rich projectiles and fragments. The COFRA results suggest that the fragmentation of neutron-rich projectiles could be most useful for producing extremely neutron-rich nuclei, taking advantage of high-intensity neutronrich RNBsÕ not very far from the final nuclei of interest, and allowing the production of refractory elements with short lifetimes. 3.2. Driver accelerator The results of this task group are presented in the accompanying contribution of Mueller [17]. They include the following elements: (1) the choice of a 1 GeV, 5 MW, CW superconducing proton linac as the base-line driver accelerator; (2) the identification of the R&DsÕ which will have to be carried out in phase 2 of the project (Section 1 above) for the driver accelerator; (3) the identification of synergies with other major European projects (Section 1 above), at least at the level of common R&DsÕ on superconducting cavities, and possibly by sharing the driver accelerator; (4) the ability, and limitations, of the base-line proton linac to accelerate heavy ions; (5) a comparison between the base-line proton linac and an electron linac for producing very-high neutron fluxes. Price estimates have been made for the base-line proton linac and its various possible extentions (to 2 GeV proton energy, for the acceleration of heavy ions . . .). 3.3. Target–ion source assembly Parts of the results of this task group are presented in other contributions to this Conference, by Helge Ravn [18] and Ulli Koester [19]. The following topics have been, and are still being,
examined: (1) the optimization of the production of neutrons by proton and deuteron beams on various targets; (2) the design of a neutron-producing target able to withstand MW beam powers. This work has clear synergies with other major European projects, like the ESS, the TNW (e.g. the MEGAPIE experiment at the PSI, Villigen, Switzerland), the neutrino factory, . . .; (3) the design of a fission target, surrounding the neutron-producing target; (4) the investigation and optimization of the efficiencies and delays involved in the diffusion and effusion of the radioactive atoms out of the target towards the ion source; (5) a study [20] of the intensity limitations of a gas cell for stopping, storing and guiding of radioactive ions. Work on ion sources is going on within another RTD project, also supported by the European Commission, called CHARGE BREEDING, wherein various methods to increase the charge of 1þ ions are experimentally investigated. Other RTD projects, related to the work of this task group, have recently been supported by the European Commission, and have started working. TARGISOL will be devoted to the optimization of the release properties of ISOL targets, especially the release speed. It will: elaborate a large database on the diffusion and desorption data, supplemented by further measurements; design, with a Monte Carlo programme, dedicated targets for the optimized release of some key elements; and test these targets online at existing RNB facilities. ION CATCHER will investigate complementary schemes for the slowing down of energetic (i.e. with fragmentation energies) radioactive ions, and for their subsequent stopping in and extraction from a gas cell or a liquid helium cell. These 2 projects are already running RTD programmes along the lines defined in Section 1 for phase 2. 3.4. Mass-selection system and post-accelerator This task group has first examined the separation techniques for radioactive ions, and proposed a new concept for such a separator at low energy, based on time-of-flight, which looks promising but requires further R&D. The various possible post-accelerators based on cyclotrons, i.e.
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a room-temperature two-cyclotron solution (similar to the present GANIL), a superconducting (SC) compact cyclotron (an upgraded version of the NSCL K1200 cyclotron) and a superconducting separated-sector cyclotron, have been examined and compared, and their respective costs estimated. A detailed study was carried out on a superconducting linac, based on the most recent achievements in SC cavities, with independently phased cavities and multiple-charge beam transport. The later option, although more expensive for the total price, has many advantages: acceleration to all energies up to 100 MeV per nucleon up to A ¼ 132; large efficiency and multiple-charge state acceleration; acceptance of a wide variety of initial charge states from the ion source; modularity; high-intensity beam capability. Even the cost, when divided by the transmission, is competitive with most cyclotron solutions. The required RTDsÕ on SC cavities and the synergies with other projects have also been identified.
•
•
•
responding RTD project AGATA (Advanced GAmma Tracking Array). The instrumentation for reaction studies with RNBsÕ will include an array for light charged particles and c-ray measurements (GRAPA, Gamma Ray And Particle Array), a 4-p array for nuclear matter studies (FAZIA, Four A and Z identification Array), a neutron-detection array, detection of fission fragments, special target developments (liquid or solid H and He targets, including a polarized 3 He target), development of special electronics. Ions and charge-particle spectrometers will comprises gas-filled separators, recoil-mass spectrometers, ray-tracing spectrometers, and their associated detectors. A special attention has been paid to a possible new development, which would aim at studying muonic and antiprotonic radioactive atoms, and which would take advantage of the simultaneous availability, on the same site, of very intense RNBsÕ and muon and antiproton beams. The electronic and data acquisition to be associated with these various instruments has also been investigated.
3.5. Instrumentation
•
This task group has made a detailed survey, with estimates of some of the corresponding prices, of the scientific instrumentation which will be required near the EURISOL facility. This includes the following items:
3.6. Cost estimates and final report
• The techniques for studying ground-state properties will include measurements of nuclear masses (Penning trap, multi-pass time-of-flight spectrometer, . . .), nuclear moments (laser spectroscopy, nuclear magnetic resonance on-line, level-mixing resonance, . . .), matter and charge radii, and studies of fundamental interactions and symmetries. • The instrumentation required for nuclear structure studies will comprises in-beam c-ray spectroscopy (including light charged particle detectors), in-beam electron spectroscopy, decay spectroscopy (including decay tagging), beta-delayed neutron spectroscopy, . . . The tagging technique is the subject of an EC supported RTD programme: EXOTAG. • A major development will have to be carried out on c-ray tracking techniques, with the cor-
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These tasks still have to be carried out. Partial cost estimates already exist for some parts of the proposed facility (e.g. the driver accelerator, the mass-selection system and post-accelerator, some components of the scientific instrumentation, . . .), but important items still have to be costed (e.g. the target–ion source system).
4. Perspectives and conclusions The EURISOL project, during its last 112 year (until 31 December 2003), still has to complete the following tasks: • Terminate the work on the target–ion source assembly, in particular to propose a layout for this assembly, including the target-handling system and the huge shielding which will be required, and to make a cost estimate for it.
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• Elaborate the RTD proposals on critical technical problems related to the projected EURISOL facility, identified so far, and submit them to the European Commission for financial support. • Identify the possible sites for EURISOL in Europe, through calls for proposals and bids from potential host laboratories, leading to a refinement of the cost estimates for EURISOL. • Follow up the progresses of the running RTDsÕ related to EURISOL, e.g. CHARGE BREEDING, TARGISOL, ION CATCHER (see Section 3.3 above), EXOTAG (see Section 3.5. above), . . . • Complete the Cost estimates and write the Final Report (see Section 3.6 above). • Start preliminary contacts with the Member States of the European Union towards a possible financing of the proposed EURISOL facility by these Member States. A new mechanism has recently been started by the European Commission, through the creation of a so-called ‘‘European Strategy Forum’’ between the Member States. A final town Meeting will also take place at the end of the work. The EURISOL project is thus progressing, at a reasonable pace, towards the construction, in Europe, of a next-generation ISOL/RNB facility, along the lines of the recommendation of the OECD Megascience Forum Working Group on Nuclear Physics cited in Section 1 above. Acknowledgements The present work is supported by the European Commission through contract HPRI-CT-199950001.
References [1] The OECD Megascience Forum: Report from the Working Group on Nuclear Physics, OECD, Paris, France, 1999. [2] A. Shotter, Advances at ISOL Facilities, these Proceedings. [3] P. Schmor, The ISAC Facility, these Proceedings; J.M. Poutissou, Overview of ISAC Science Program, these Proceedings. [4] D. Morrisey, Commissioning of the NSCL A 1900 Fragment Separator, these Proceedings, 70. [5] B. Sherril, Overview of the RIA Project, these Proceedings, 136. [6] G. Savard, Status of the R&D for the RIA Project, these Proceedings, 93. [7] T. Kubo, PF Separator Big RIPS at RIKEN and Elsewhere in Japan, these Proceedings, 52. [8] Y. Yano, RI Beam Factory Project at RIKEN, these Proceedings, 149. [9] H. Geissel, Present and Next Generation RB Facility at GSI, these Proceedings, 29. [10] W. Henning, Plans for the Future facility at GSI, these Proceedings, 133. [11] J. Nolen, Proc. 3rd Int. Conf. on RNB, Gif-sur-Yvette, France, 1993, p. 111. [12] B. Jonson et al., Report to the EURISOL Group on Key Experiments, unpublished; J. Vervier, unpublished calculations. [13] K. S€ ummerer, B. Blank, Phys. Rev. C 61 (2000) 034607. [14] J. Benlliure et al., GSI-preprint 00-41. Available from. [15] J.-J. Gaimard, K.-H. Schmidt, Nucl. Phys. A 531 (1991) 709. [16] J. Benlliure et al., Nucl. Phys. A 660 (1999) 87. [17] A. Mueller, Future High Intensity ISOL Facilities: selected current R&D topics and possible synergies with other projects, these Proceedings, 73. [18] H. Ravn, Advanced Target Concept for Production of Beams of Neutrinos and Radioactive Ions, these Proceedings, 87. [19] U. Koester et al., Production and use of oxide fiber targets at ISOLDE, these Proceedings, 47. [20] M. Huyse et al., Intensity limitations of a gas cell for stopping, storing and guiding of radioactive ions. .
Status of the EURISOL project Jean Vervier
*
Institut de Physique Nucl eaire, Chemin de Cyclotron 2, Universit e Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
Abstract EURISOL is a preliminary design study of the European next-generation isotope separation on line (ISOL) radioactive nuclear beam (RNB) facility, which should extend and amplify, beyond 2010, the exciting work presently carried out with the first-generation ISOL/RNB facilities in Europe and all around the world. The present paper presents a status report, as to 1 May 2002, on the various tasks identified within the project. 2003 Elsevier Science B.V. All rights reserved. PACS: 20.29.90.+r
1. Introduction In 1999, the OECD Megascience Forum Working Group on Nuclear Physics, which included representatives from OECD Member countries all around the world, issued a Report [1], with a Section on radioactive nuclear beam (RNB) facilities. This Section includes the following recommendation: ‘‘The Working Group recognises the importance of RNB facilities for a broad programme of research in fundamental nuclear physics and astrophysics, as well as applications of nuclear science. A new generation of high-intensity RNB facilities of each of the two basic types, ISOL and In-Flight, should be built on a regional basis. Interested governments are encouraged to undertake the necessary decisions within the next few years, and the facilities themselves should become operational in 5–10 years’’. This 1999 recommendation is progressively coming into practice, as shown by the many *
Tel.: +32-10-416596; fax: +32-10-452183. E-mail address: [email protected] (J. Vervier).
projects of next-generation RNB facilities discussed during the present EMIS-14 Conference. In North-America, ISAC-1 started operation at TRIUMF, Vancouver, Canada, and ISAC-2 has been approved [2,3]. In the United States, progresses have been made at the In-Flight facility of the National Superconducting Cyclotron Laboratory [4]; the Rare Isotope Accelerator RIA project has been elaborated, R and D on some of its critical components has started and the project includes an In-Flight component [5,6]. At RIKEN, Japan, a next-generation In-Flight facility is under construction [7,8]. In Europe, a major upgrade of the In-Flight facility at the GSI, Darmstadt, Germany is proposed [9,10]. Against this background, the EURISOL project, supported by the European Commission, aims at a preliminary design study of the next-generation European ISOL/RNB facility which should extend and amplify, beyond 2010, the exciting work presently carried out with the first-generation ISOL/RNB facilities, operating or under construction, in Europe and all around the world, as illustrated in many talks during the present EMIS-14 Conference.
0168-583X/03/$ - see front matter 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(03)00499-3
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The EURISOL project associates ten European Nuclear Physics laboratories, i.e.: GANIL, Caen, France; the Chalmers University of Technology (CUT), G€ oteborg, Sweden; the Katholieke Universiteit Leuven (KULeuven), Leuven, Belgium; GSI, Darmstadt, Germany; the Instituto Nazionale di Fisica Nucleare (INFN), Roma, Italy (and in particular, the Laboratori Nazionale di Legnaro, Padova, Italy); the Institut de Physique Nucleaire (IPNO), Orsay, France; the CEA/DAPNIA, Saclay, France; ISOLDE/CERN, Geneve, Switzerland; the Accelerator Laboratory (JYFL), Jyv€ askyl€ a, Finland; the Rutherford-Appleton Laboratory (RAL), Didcot, United Kingdom. The Project started on January 1, 2000 and should conclude its work by December 31, 2003. It is a preliminary design study (phase 1), which should be followed by RTD programmes, starting in 2002 and lasting 4–5 years (phase 2), and by a full engineering design of the proposed facility, leading, hopefully, to its commissioning around the year 2010 (phase 3). The following tasks have been identified for the EURISOL programme: • The identification of key experiments to be performed with the proposed facility, and the definition of their requirements, in terms of the types, energies and intensities of the needed RNBsÕ. This task is coordinated by CUT (Bjorn Jonson). • The definition of the driver accelerator, which will produce the radioactive nuclei. This task is coordinated by IPNO (Alex Mueller). • The investigation of the target–ion source assembly, wherein the radioactive nuclei will be produced and ionized. This task is coordinated by ISOLDE/CERN (Helge Ravn). • The definition of the mass-selection system and post-accelerator, which will select the radioactive ions according to their masses and bring them to the desired energies. This task is coordinated by GANIL (Eric Baron and MarieHelene Moscatello). • The identification of the scientific instrumentation to be used near the planned facility, to perform, in particular, the key experiments. This € yst€ task is coordinated by JYFL Juha A o.
• The elaboration of the cost estimates of the proposed facility, construction and running costs, hopefully at the 20% level, and of the final report of the project. This will be carried out by all the participants to the EURISOL project, in particular the Scientific Coordinator (Jean Vervier) and the Technical Coordinator (John Cornell). Within the various tasks just listed, special attention has been paid to the following three points: • The identification of the RTD programmes, on crucial technical points related to the proposed facility, which will have to be carried out in phase 2 of the project (see above) before the full engineering design of phase 3. • The identification of synergies between the proposed facility and other major European projects or laboratories. These projects include: the European spallation source (ESS); the transmutation of nuclear wastes (TNW); the neutrino factory within the High Energy Physics programmes, . . . • The study should, in a first phase, be site independent. In the present paper, we successively present: the main options which have been taken for the proposed EURISOL project; the progresses made in the various tasks identified above; the future perspectives of the project during the next few years.
2. Main options for the EURISOL project There are many different ways to produce RNBsÕ by the ISOL method, depending on the type and energy of the projectiles produced by the driver, on the target and ion source, and on the energy of the post-accelerator. In order to guide the work of the various groups in charge of the tasks defined in Section 1, the Steering Committee of the EURISOL project, which includes representatives of the 10 laboratories associated to the project and the coordinators of the task groups, has taken the following main options:
J. Vervier / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 759–764
• The widest scientific field wherein key experiments are likely to be performed lies in the neutron-rich region of the periodic table, although the proton-rich region should not be neglected. This means that fission will be an important mode of production of the radioactive nuclei, together with spallation. • The driver accelerator should produce protons, at energies around 1 GeV, with very high intensities, in the several mA range, i.e. with very high beam powers, around 5 MW. Such beams will be used in two ways: either, by sending the full beam power on a suitable target, to produce very high fluxes of fast neutrons, which will in turn induce fission in a uranium target, yielding at least 1015 fissions per second, i.e. very large quantities of neutron-rich radioactive nuclei (this is the so-called indirect method [11]); or by sending a fraction of the beam intensity, at least 100 lA, directly on a spallation target, producing thereby mostly proton-rich nuclei. The performances of the driver for accelerating other particles than protons, with a mass-tocharge ratio of 2, should be studied, and the possibility of using, as driver, a high-energy (50–70 MeV), high-intensity (20–30 mA) electron accelerator (which could induce photofission in a secondary uranium target through the bremsstrahlung of the electron beam in a primary target) should be investigated. • Various types for the target–ion source assembly should therefore be investigated: a very high-power neutron-producing target; a fission target for at least 1015 fissions per sec; a spallation target for at least 100 lA of 1 GeV protons; and the associated ion sources. Special attention should be paid to the efficiencies of these various components, in particular to the minimization of the losses due to the delay times involved in the diffusion and effusion processes out of the target and towards the ion source, and to the chemical selectivity during these processes. • The mass-selection system and post-accelerator should select the ions according to their masses, hopefully separating isobars, and produce RNBsÕ in three different energy regions: (i) at very low energies (tens of keV), for ‘‘ISOLDE’’ types of experiments; (ii) at intermediate ener-
761
gies, up to about 10 MeV per nucleon, for fusion–evaporation reactions, Coulomb excitation, transfer reactions, nuclear astrophysics experiments, . . .; (iii) at high energies, up to 100 MeV per nucleon up to A 100, for fragmenting RNBsÕ, investigating the nuclear equation of state (EOS), . . . • The scientific instrumentation should be adapted to the proposed key experiments and to the planned energies of the RNBsÕ. These options have been presented, and discussed, to the European scientific community on Nuclear Structure at the occasion of two Town Meetings, at Orsay, France, on 6–7 November 2000 and Abano Terme, Italy, on 24–25 January 2002, where the partial results already obtained were also reviewed.
3. Progresses in the various tasks of EURISOL 3.1. Key experiments There are, by now, several detailed Reports on the various topics in Nuclear Physics, Nuclear Astrophysics, Fundamental Interactions and Applications of Nuclear Science which will be addressed by the next-generation RNB facilities, ISOL and In-Flight. The key experiments task group concentrated on some of these topics: (1) nuclear structure far from stability, i.e. the position of the proton and neutron driplines, radioactive decays far from stability, changes in the shell structures, halo nuclei, heavy and superheavy nuclei; (2) nuclear reactions with RNBsÕ, mostly one-, two- and multiple-nucleon transfers; (3) high-spin physics in exotic nuclei; (4) the nuclear EOS for different isospins; (5) nuclear astrophysics; (6) tests of the Standard Model and of fundamental conservation laws. One of the topics examined by the key experiments task group was the production of very exotic neutron-rich nuclei by fragmenting very high fluxes (e.g. 1011 particles per second) of neutronrich RNBsÕ post-accelerated to energies around 100 MeV per nucleon. The first calculations [12] were carried out using the modified EPAX formula
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[13]. A further investigation, by the group of Karl– Heinz Schmidt at GSI [14], used more sophisticated and hopefully more physical codes, based on the abrasion–ablation model, i.e. ABRABLA [15], which uses a Monte Carlo simulation, and COFRA [16], a simplified, analytical version of ABRABLA. The comparison of these codes [13,16] between themselves and with the experimental data shows that the EPAX formula is reasonably successful for predicting the fragmentation of stable projectiles, but overestimates the cross-sections for neutron-rich projectiles and fragments. The COFRA results suggest that the fragmentation of neutron-rich projectiles could be most useful for producing extremely neutron-rich nuclei, taking advantage of high-intensity neutronrich RNBsÕ not very far from the final nuclei of interest, and allowing the production of refractory elements with short lifetimes. 3.2. Driver accelerator The results of this task group are presented in the accompanying contribution of Mueller [17]. They include the following elements: (1) the choice of a 1 GeV, 5 MW, CW superconducing proton linac as the base-line driver accelerator; (2) the identification of the R&DsÕ which will have to be carried out in phase 2 of the project (Section 1 above) for the driver accelerator; (3) the identification of synergies with other major European projects (Section 1 above), at least at the level of common R&DsÕ on superconducting cavities, and possibly by sharing the driver accelerator; (4) the ability, and limitations, of the base-line proton linac to accelerate heavy ions; (5) a comparison between the base-line proton linac and an electron linac for producing very-high neutron fluxes. Price estimates have been made for the base-line proton linac and its various possible extentions (to 2 GeV proton energy, for the acceleration of heavy ions . . .). 3.3. Target–ion source assembly Parts of the results of this task group are presented in other contributions to this Conference, by Helge Ravn [18] and Ulli Koester [19]. The following topics have been, and are still being,
examined: (1) the optimization of the production of neutrons by proton and deuteron beams on various targets; (2) the design of a neutron-producing target able to withstand MW beam powers. This work has clear synergies with other major European projects, like the ESS, the TNW (e.g. the MEGAPIE experiment at the PSI, Villigen, Switzerland), the neutrino factory, . . .; (3) the design of a fission target, surrounding the neutron-producing target; (4) the investigation and optimization of the efficiencies and delays involved in the diffusion and effusion of the radioactive atoms out of the target towards the ion source; (5) a study [20] of the intensity limitations of a gas cell for stopping, storing and guiding of radioactive ions. Work on ion sources is going on within another RTD project, also supported by the European Commission, called CHARGE BREEDING, wherein various methods to increase the charge of 1þ ions are experimentally investigated. Other RTD projects, related to the work of this task group, have recently been supported by the European Commission, and have started working. TARGISOL will be devoted to the optimization of the release properties of ISOL targets, especially the release speed. It will: elaborate a large database on the diffusion and desorption data, supplemented by further measurements; design, with a Monte Carlo programme, dedicated targets for the optimized release of some key elements; and test these targets online at existing RNB facilities. ION CATCHER will investigate complementary schemes for the slowing down of energetic (i.e. with fragmentation energies) radioactive ions, and for their subsequent stopping in and extraction from a gas cell or a liquid helium cell. These 2 projects are already running RTD programmes along the lines defined in Section 1 for phase 2. 3.4. Mass-selection system and post-accelerator This task group has first examined the separation techniques for radioactive ions, and proposed a new concept for such a separator at low energy, based on time-of-flight, which looks promising but requires further R&D. The various possible post-accelerators based on cyclotrons, i.e.
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a room-temperature two-cyclotron solution (similar to the present GANIL), a superconducting (SC) compact cyclotron (an upgraded version of the NSCL K1200 cyclotron) and a superconducting separated-sector cyclotron, have been examined and compared, and their respective costs estimated. A detailed study was carried out on a superconducting linac, based on the most recent achievements in SC cavities, with independently phased cavities and multiple-charge beam transport. The later option, although more expensive for the total price, has many advantages: acceleration to all energies up to 100 MeV per nucleon up to A ¼ 132; large efficiency and multiple-charge state acceleration; acceptance of a wide variety of initial charge states from the ion source; modularity; high-intensity beam capability. Even the cost, when divided by the transmission, is competitive with most cyclotron solutions. The required RTDsÕ on SC cavities and the synergies with other projects have also been identified.
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•
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responding RTD project AGATA (Advanced GAmma Tracking Array). The instrumentation for reaction studies with RNBsÕ will include an array for light charged particles and c-ray measurements (GRAPA, Gamma Ray And Particle Array), a 4-p array for nuclear matter studies (FAZIA, Four A and Z identification Array), a neutron-detection array, detection of fission fragments, special target developments (liquid or solid H and He targets, including a polarized 3 He target), development of special electronics. Ions and charge-particle spectrometers will comprises gas-filled separators, recoil-mass spectrometers, ray-tracing spectrometers, and their associated detectors. A special attention has been paid to a possible new development, which would aim at studying muonic and antiprotonic radioactive atoms, and which would take advantage of the simultaneous availability, on the same site, of very intense RNBsÕ and muon and antiproton beams. The electronic and data acquisition to be associated with these various instruments has also been investigated.
3.5. Instrumentation
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This task group has made a detailed survey, with estimates of some of the corresponding prices, of the scientific instrumentation which will be required near the EURISOL facility. This includes the following items:
3.6. Cost estimates and final report
• The techniques for studying ground-state properties will include measurements of nuclear masses (Penning trap, multi-pass time-of-flight spectrometer, . . .), nuclear moments (laser spectroscopy, nuclear magnetic resonance on-line, level-mixing resonance, . . .), matter and charge radii, and studies of fundamental interactions and symmetries. • The instrumentation required for nuclear structure studies will comprises in-beam c-ray spectroscopy (including light charged particle detectors), in-beam electron spectroscopy, decay spectroscopy (including decay tagging), beta-delayed neutron spectroscopy, . . . The tagging technique is the subject of an EC supported RTD programme: EXOTAG. • A major development will have to be carried out on c-ray tracking techniques, with the cor-
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These tasks still have to be carried out. Partial cost estimates already exist for some parts of the proposed facility (e.g. the driver accelerator, the mass-selection system and post-accelerator, some components of the scientific instrumentation, . . .), but important items still have to be costed (e.g. the target–ion source system).
4. Perspectives and conclusions The EURISOL project, during its last 112 year (until 31 December 2003), still has to complete the following tasks: • Terminate the work on the target–ion source assembly, in particular to propose a layout for this assembly, including the target-handling system and the huge shielding which will be required, and to make a cost estimate for it.
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• Elaborate the RTD proposals on critical technical problems related to the projected EURISOL facility, identified so far, and submit them to the European Commission for financial support. • Identify the possible sites for EURISOL in Europe, through calls for proposals and bids from potential host laboratories, leading to a refinement of the cost estimates for EURISOL. • Follow up the progresses of the running RTDsÕ related to EURISOL, e.g. CHARGE BREEDING, TARGISOL, ION CATCHER (see Section 3.3 above), EXOTAG (see Section 3.5. above), . . . • Complete the Cost estimates and write the Final Report (see Section 3.6 above). • Start preliminary contacts with the Member States of the European Union towards a possible financing of the proposed EURISOL facility by these Member States. A new mechanism has recently been started by the European Commission, through the creation of a so-called ‘‘European Strategy Forum’’ between the Member States. A final town Meeting will also take place at the end of the work. The EURISOL project is thus progressing, at a reasonable pace, towards the construction, in Europe, of a next-generation ISOL/RNB facility, along the lines of the recommendation of the OECD Megascience Forum Working Group on Nuclear Physics cited in Section 1 above. Acknowledgements The present work is supported by the European Commission through contract HPRI-CT-199950001.
References [1] The OECD Megascience Forum: Report from the Working Group on Nuclear Physics, OECD, Paris, France, 1999. [2] A. Shotter, Advances at ISOL Facilities, these Proceedings. [3] P. Schmor, The ISAC Facility, these Proceedings; J.M. Poutissou, Overview of ISAC Science Program, these Proceedings. [4] D. Morrisey, Commissioning of the NSCL A 1900 Fragment Separator, these Proceedings, 70. [5] B. Sherril, Overview of the RIA Project, these Proceedings, 136. [6] G. Savard, Status of the R&D for the RIA Project, these Proceedings, 93. [7] T. Kubo, PF Separator Big RIPS at RIKEN and Elsewhere in Japan, these Proceedings, 52. [8] Y. Yano, RI Beam Factory Project at RIKEN, these Proceedings, 149. [9] H. Geissel, Present and Next Generation RB Facility at GSI, these Proceedings, 29. [10] W. Henning, Plans for the Future facility at GSI, these Proceedings, 133. [11] J. Nolen, Proc. 3rd Int. Conf. on RNB, Gif-sur-Yvette, France, 1993, p. 111. [12] B. Jonson et al., Report to the EURISOL Group on Key Experiments, unpublished; J. Vervier, unpublished calculations. [13] K. S€ ummerer, B. Blank, Phys. Rev. C 61 (2000) 034607. [14] J. Benlliure et al., GSI-preprint 00-41. Available from