Neutron-rich nuclei and fission; recent developments and future aspects

Production and studies of neutron-rich nuclei produced in fission are reviewed. Some recent experiments performed with the ISOL technique at the IGISOL and the ISOLDE facilities are reviewed. The manipulation of neutron-rich nuclei is discussed with a special focus on radioactive ion cooling and trapping techniques under construction worldwide. Perspectives of obtaining intense post accelarated beams of fission products are discussed. Received: 1 May 2001 / Accepted: 4 December 2001     

Prospects for exotic beam facilities in North America

There are several nuclear physics laboratories in North America that have on-going research using energetic and stopped radioactive beams. These include the large ISOL-type programs ISAC at TRIUMF and HRIBF at Oak Ridge and the in-flight fragmentation program at the NSCL of Michigan State University. There are also smaller, more specialized, programs using a variety of techniques at the 88-inch cyclotron of Berkeley, ATLAS at Argonne, the Cyclotron Institute of Texas A&M University, the Nuclear Structure Laboratory at Notre Dame University, and the Nuclear Structure Laboratory at SUNY/Stony Brook. There are also three projects on the horizon in North America for new capabilities in both the near term and more distant future. The intensities of the in-flight fragment beams at the NSCL will be increased dramatically very soon as the Coupled Cyclotron Project will be completed and commissioned for research by mid-2001. A new project, ISAC-II, has been approved in Canada. For the longer term, the United States is considering construction of a major new facility, the Rare Isotope Accelerator (RIA), which would have a very high-intensity heavy-ion driver linac. The RIA facility is proposed to utilize both ISOL and in-flight production mechanisms. Received: 1 May 2001 / Accepted: 4 December 2001     

Intense radioactive-ion beams produced with the ISOL method

For fifty years the isotope separation on-line (ISOL) technique has been used for the production of radioactive-ion beams (RIBs). Thick-target ISOL facilities can provide very intense RIBs for a wide range of applications. The important design parameters for an ISOL facility are efficiency, rapidity and selectivity of all steps of the separation process. To achieve the anticipated beam intensities with the next-generation RIB facilities, the production rate in the ISOL target has to be increased by orders of magnitude. This is only possible by adapting the projectile beam for optimum production cross-sections and simultaneously minimizing the target heating due to the electronic stopping power of charged-particle projectiles. ISOL beams of 75 different elements have been produced up to now and further beam development is under way to produce a still greater variety of isotopes and to improve existing beams in intensity and purity. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: Ulli.Koster@cern.ch     

Giant-resonance studies with radioactive beams: Perspectives

First-generation radioactive ion-beam facilities have already been in operation for some time. Advanced facilities that will deliver high-intensity radioactive nuclear beams ranging in energy from below the Coulomb barrier to up to several hundred MeV per nucleon (MeV/u) are either starting operation, or under construction or in the planning stage. In this paper the perspectives of using radioactive nuclear beams to study giant resonances in nuclei far from the valley of stability are explored. In particular, emphasis will be made on information on certain nuclear properties that can be gained from such studies. Received: 1 May 2001 / Accepted: 4 December 2001     

Challenge towards muonic atom formation with unstable nuclei

X-ray spectroscopy of muonic atoms is an important tool to obtain information on the nuclear charge distribution of nuclei. It has been successfully used for many years to study stable isotopes in condensed or gaseous states. A new method has been proposed to extend muonic atom X-ray spectroscopy to the use of radioactive isotope beams to form muonic atoms with unstable nuclei. This new method allows studies of the nuclear properties and nuclear sizes of unstable atoms by means of the muonic X-ray method at facilities where both negative muon and radioactive nuclear beams would be available. Progress of a feasibility study at RIKEN-RAL muon facility is also reported. Received: 1 May 2001 / Accepted: 4 December 2001     

利用强流ISOL束研究20Na的奇异衰变模式(英文)

北京放射性离子束装置（Beijing Radioactive Ion-beam Facility,BRIF）是基于在线同位素分离器技术的国家大科学平台。在BRIF装置上利用100 MeV的质子束轰击较厚的反应靶产生放射性核素;反应产物经离子源电离和在线分离,在线同位素分离段可引出100~300 keV的放射性核束,质量分辨率达20 000。在基金委科学仪器基础研究专项的支持下,建成了多用途的衰变实验终端,包括束流传输管道、通用靶室、带电粒子和γ探测器、集成电子学和数据获取系统等。利用100 MeV的质子束轰击MgO厚靶产生了流强高达1×105 pps的20Na放射性核束。通过高效率地同时测量β,γ和α,第一次直接观测到20Na非常稀有的β-γ-α衰变模式。Beijing Radioactive Ion-beam Facility(BRIF) has been commissioned as the national Radioactive Ion Beam(RIB) facility based on the Isotope Separator On Line(ISOL) technique since 2016. At BRIF, the radioactive nuclides are produced by the proton beam of 100 MeV bombarding a thick-target, the reaction products diffusing out of the target are ionized by an ion source and delivered to the online mass separator. In addition to the post-accelerated radioactive ion beams, BRIF can provide low-energy ISOL beams of 100 to 300 keV with a mass resolution of 20 000. A general-purpose decay station has been built including the ISOL beam transport line, a conventional reaction chamber, charge-particle and γ detectors with integrated electronics and data acquisition system. An intense 20Na ISOL beam up to 1×105 pps was produced by using the 100 MeV proton beam bombarding a MgO thick target. With high-efficiency measurements of β, γ and α simultaneously, very rare β-γ-α decay mode in 20Na has been directly observed for the first time in the present work.     

Direct mass measurements of exotic nuclei

The present status and recent results from direct mass measurements of exotic nuclei are presented. ISOL, in-flight, and combined facilities provide a wide variety of nuclides far-off stability covering a wide range of half-lives down to the sub-millisecond region. Modern direct mass measurements are carried out using frequency and time-of-flight techniques. The obtained accurate mass data point to nuclear-structure phenomena and serve as a basis for astrophysical and weak-interaction studies. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: c.scheidenberger@gsi.de     

CIAE重离子加速器物理研究平台

中国原子能科学研究院正在规划中的重离子加速器物理研究平台的基本方案是在 现有的HI-13串列加速器的后端新建一台能量增益为18MeV/q的重离子超导直线加速器.超导直线加速器包括: 36个铜铌溅射型四分之一波长(QWR)谐振腔; 9个恒温柜, 及一系列等时性消色散束流传输系统. 同时配套建设一条与现有的HI-13串列加速器相并列的重离子四杆型射频四极加速器——RFQ和交叉手指型漂移管直线加速器IH-DTL接受来自ISOL的正离子束,然后直接注入到超导直线加速器.     

Radioactive ions for solid-state investigations at magnetic surfaces and interfaces

Hyperfine interactions observed at isomeric states of radioactive probe nuclei are used as a tool for solid-state investigations. This method is sensitive to atomic-scale properties. In recent years surface and interface investigations using radioactive probes delivered many results which can hardly be achieved by any other method. Several groups, e.g., from Konstanz, Leuven, Groningen, Aarhus, Uppsala, Tel Aviv, Pennsylvania, contributed to this field. Our group studies magnetic properties at surfaces and interfaces performing perturbed angular correlation (PAC) measurements in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN). We take advantage of the enhanced variety of PAC probes delivered by the on-line mass separator ISOLDE. First, we report on measurements of magnetic hyperfine fields ( B _hf) at Se adatoms on a ferromagnetic substrate using ⁷⁷Se as a PAC probe. The investigation of induced magnetic interactions in nonmagnetic materials is a further subject of our studies. Here the nonmagnetic 4d element Pd is investigated, when it is in contact with ferromagnetic nickel. An outlook will be given on studies to be done in the future. The experiments were performed at the HMI, Berlin, and at CERN, Geneva. Received: 1 May 2001 / Accepted: 4 December 2001     

Power Supplies of Correction Magnets of Modern Accelerating Complexes

Physics of Particles and Nuclei Letters - The Budker Institute of Nuclear Physics has been designing two accelerator facilities of the MegaScience class [1, 2]. It is planned to use the same...     

EURISOL Desktop Assistant Toolkit (EDAT): A modeling,simulation and visualization support to the preliminary radiological assessment of RIB projects

The paper describes an approach taken within the EURISOL-DS project (European Isotope Separation Online Radioactive Ion Beam Facility) to a number of safety and radioprotection issues raised by the advent of radioactive ion beam facilities in the cutting edge area of particle accelerators. The ensuing solution emerged from a collaborative effort of the investigating team-in-charge, affiliated with the Horia Hulubei National Institute of Physics and Nuclear Engineering in Bucharest, with expert colleagues at the Physics Institute in Vilnius, and at CERN, within the participation in the EURISOL-DS project, Sub-Task B: Radiation, Activation, Shielding and Doses of the Safety and Radioprotection, Task 5. The work was primarily geared towards the identification of knowledge and data in line with validated, accepted and nationally/internationally recommended methods and models of radiological assessment applied within the nuclear power fuel cycle, deemed to be suitable for assessing health and environmental impact of accelerator operations as well. As a result, a computer software platform code-named “EURISOL Desktop Assistant Toolkit” was developed. The software is, inter alia, capable to assess radiation doses from pure or isotopically mixed open or shielded point sources; emergency response-relevant doses; critical group doses via complex pathways, including the air, the water, and the food chain and derived release limits for the normal, routine operations of nuclear facilities. Dedicated data libraries and GIS (Geographic Information System) facilities assist the input/output operations.     

Photofission for the production of radioactive beams: Experimental data from an on-line measurement

A PARRNe 1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) aimed at the production of neutron-rich radioactive noble gases produced by photofission has been performed at CERN. The LEP Pre-Injector (LPI) has been used to deliver a 50 MeV electron beam. The results obtained show clearly that the use of an electron beam to produce neutron-rich fission fragments for futur RNB facilities is an option that should not be neglected. Received: 20 July 2001 / Accepted: 5 June 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: ibrahim@ipno.in2p3.fr Communicated by D. Guerreau     

Secondary-beam production: Protons versus heavy ions

The construction of two new-generation complementary RIB facilities in Europe, one based on the in-flight fragmentation or fission (IFF) method (FAIR) and the other on the isotope separation on-line (ISOL) method (EURISOL) is expected in the next 10-15 years. The reaction mechanisms, responsible for the production of the secondary nuclei, along with the technical constrains, have to be considered for the designs of the facilities. In this work, we study which reaction mechanisms can be exploited at best for the production of the secondary beams in the two facilities.     

Synthesis and decay properties of superheavy atoms in nuclear reactions induced by stable and radioactive ion beams

This talk consists of two parts. The first one presents the results of investigations performed in 1998-2000 in Dubna on the synthesis of superheavy nuclei in reactions induced by ⁴⁸Ca ions. The radioactive decay properties of the nuclei, indicating a considerable increase in the α-decay and spontaneous fission half-lives of the isotopes of elements 110-116 when approaching the closed neutron shell at N = 184, are given. In the second part the possible ways of advancing into the region of more neutron-rich nuclei, using stable and radioactive ion beams, are discussed. Since so far no intense radioactive ion beams are available, some experiments with stable beams are considered as a test for the suggested ideas. Received: 1 May 2001 / Accepted: 4 December 2001     

Production of low- and high-energy radioactive-ion beams by fragmentation

The physics opportunities made possible by beams of rare isotopes are among the richest available in nuclear science. The rare-isotope accelerator (RIA) now under development is an innovative accelerator that will define the state of the art for all such facilities. A novel aspect of the RIA project is the conversion of the most intense high-energy heavy-ion beams into both fast and reaccelerated exotic beams. Along with target fragmentation in next-generation high-power ISOL targets, RIA will use projectile fragmentation in a high-energy separator/gas-filled ion collector system to provide an extensive range of thermalized ions for reacceleration. In addition, a second high-energy separator will provide the same or larger range of ions for high-energy experiments. A brief overview of the RIA accelerator concept, the layout of the facility, and production techniques will be given along with information on the present R&D efforts in gaseous-ion collection. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: morrissey@nscl.msu.edu     

Solid state physics at ISOLDE

Radioactive atoms have been used in solid state physics and in materials science for decades. Besides their classical applications as tracers for diffusion studies, nuclear techniques such as Mössbauer spectroscopy, perturbedγγ angular correlation,β-NMR, and emission channeling make use of nuclear properties (via hyperfine interactions or emittedα orβ particles) to gain microscopic information on structural and dynamical properties of solids. During the last decade, the availability of many different radioactive isotopes as clean ion beams at ISOL facilities like ISOLDE/CERN has triggered a new era involving methods sensitive to the optical and electronic properties of solids, especially in the field of semiconductor physics. This overview will browse through ongoing solid state physics experiments with radioactive ion beams at ISOLDE. A wide variety of problems is under study, involving bulk properties, surfaces and interfaces in many different systems like semiconductors, superconductors, magnetic systems, metals and ceramics.

     

Diamagnetic interactions in disordered suspensions of metastable superconducting granules

The simulation of the transition sequence of superheated Type I superconducting granules (SSG) in disordered suspensions when an external magnetic field is slowly increased from zero has been studied. Simulation takes into account diamagnetic interactions and the presence of surface defects. Results have been obtained for the transition sequence and surface fields distribution covering a wide range of densities. These results are compared with previous analytical perturbative theory, which provides qualitative information on transitions and surface magnetic fields during transitions, but with a range of validity apparently limited to extremely dilute samples. Simulations taking into account the complete diamagnetic interactions between spheres appear to be a promising tool in interpreting SSG experiments, in applications such as particle detectors, and in some fundamental calculations of Solid State Physics. Received 6 April 2001 and Received in final form 15 October 2001     

Fast unstable nuclear beam facilities: present and future

A review is given of the present and future facilities for the production and acceleration of unstable nuclear beams for exciting physics research at the limits of nuclear stability. The various methods for the production of unstable beams using in-flight and ISOL techniques with thick and thin targets are discussed, including their advantages and disadvantages. Some typical examples of facilities are shown. New concepts, future research developments and proposals for ambitious large facilities to meet the challenges of the future are described. To cite this article: A.C.C. Villari, J.R.J. Bennett, C. R. Physique 4 (2003).