Radioactive Nuclear Beam Facility Research Articles

TriSol: A major upgrade of the TwinSol RNB facility

We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target.

Nuclear mass measurements

Mass is a fundamental property of atomic nuclei. Nuclear masses are widely used in nuclear physics and astrophysics researches as well as nuclear technique applications. Currently it is the mass spectrometry that dominates the research field of nuclear mass measurement. Thanks to the developments of radioactive nuclear beam facilities and novel mass spectrometers, the experimental knowledge of atomic masses is rapidly expanding along two main directions, namely measurements aimed at high-precision mass values and at the most exotic nuclei far from the stability. In this article, we will review briefly the history of nuclear mass measurements and present the current status. By evaluating all available experimental data from nuclear reactions, radioactive decays and direct mass measurements, the AME (Atomic Mass Evaluation) serves the research community with the most reliable source for comprehensive information related to the nuclear masses. The latest AME was published in March, 2017 as AME2016, which will also be introduced in this article. In recent years, based on the large-scale research facility HIRFL-CSR, we have carried out precision mass measurements for short-lived nuclides by using the isochronous mass spectrometry at Institute of Modern Physics, Chinese Academy of Sciences. We achieved the highest precision of mass measurements using the Isochronous Mass Spectrometry (IMS) method and set the world record of the shortest half-life of a nuclear state whose mass has ever been measured directly. The IMS with double-time-of-flight has been established for the first time, with which the IMS experiments will be carried out in future. Masses of more than 50 short-lived nuclides have been determined with relative mass uncertainties of 10−6–10−7. The newly obtained mass values have been used to study the relevant nuclear physics and nuclear astrophysics problems. We will discuss the impact of the mass results on investigations concerning isospin symmetry in nuclides and rp nucleosynthesis process as examples.

Beijing radioactive ion facility and basic nuclear physics research prospects

Both radioactive nuclear beam physics and nuclear astrophysics are the frontiers in basic research of physics, which promote the development of radioactive nuclear beam facilities. Here we briefly introduce radioactive nuclear beam physics and nuclear astrophysics, and compare the isotope separation on line (ISOL) and projectile fragmentation (PF) methods to produce radioactive nuclear beams. In addition, we review the pre-existing ISOL-type facilities and introduce Beijing radioactive ion facility (BRIF) and its perspective in basic research of nuclear physics.

Recent highlights on fragmentation reactions

Fragmentation reactions constitute an optimum tool for exploring the nuclear landscape by producing nuclei far from stability at in-flight radioactive nuclear beam facilities. Moreover, they are routinely used in modern cancer therapy treatments. Nevertheless, the large dynamical and isospin range covered by this reaction mechanism are unique features for many fundamental studies. In this work we review some of the most salient recent results in fundamental nuclear physics studies based on fragmentation reactions.

Study of the structure of unstable nuclei through the reaction experiments

Along with the development of the radioactive nuclear beam facility, the study of the structure of unstable nuclei has progressed rapidly over the last few decades. Due to the weakly binding property, the structure information of the unstable nuclei comes primarily from the scattering or reaction experiments. Therefore it would be very important to understand clearly the reaction mechanism involved in the experiment. We outlined here the major reaction mechanisms which are adequate to the study of unstable nuclei, with the focus on the new phenomena and methods in comparison with those with traditional stable nucleus beam. Especially emphasized are the breakup and knockout reactions, developed as accurate tools for spectroscopy investigation into the nuclear structure with low intensity secondary beam. Couplings of the breakup channel to the elastic scattering and the fusion and transfer reactions are also reviewed.

Time-of-flight energy compensation to improve energy resolution in low-energy radioactive beam experiments at the TwinSol facility

Abstract Improved time-of-flight (ToF) capability has been added to the University of Michigan (UM)–University of Notre Dame (UND) TwinSol low-energy dual 6T solenoid-based radioactive nuclear-beam (RNB) facility at the UND FN tandem Van de Graaff accelerator. An extended low-background beam line has been combined with a newly-constructed ca.1 meter diameter ISO-250 based scattering chamber capable of sub-ns ToF of RNBs. These together with the intrinsic, low ToF spread in the TwinSol ion-optical system yields improved ToF information for low-energy RNB nuclear reaction studies. Using either the intrinsic accelerator bunched and pulsed-selected beams with RF timing, or with the addition of an MCP+foil timing system (or similar) detector at the dual-solenoid cross-over region allows for reduction of the energy spread inherent in these low-energy RNB reactions. As an example, using the ToF information reduces the FWHM energy spread in a high-intensity 28 MeV 8Li beam from about 1 MeV to

Tokai Radioactive Ion Accelerator Complex (TRIAC)

An ISOL-based radioactive nuclear beam (RNB) facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly developed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to supply RNBs for experiments in 2005 and RNBs including fission fragments with energies up to 1.1MeV/A are available in the present. Several experimental studies were performed successfully using 8Li beams with various energies.

Laser spectroscopy of trapped 7Be and 10Be at a prototype slow RI-beam facility of RIKEN

A next-generation slow radioactive nuclear ion beam facility (SLOWRI) which provides slow, high-purity and small emittance ion beams of all elements is being build as one of the principal facilities at the RIKEN RI-beam factory (RIBF). High energy radioactive ion beams from the projectile fragment separator BigRIPS are thermalized in a large gas catcher cell The thermalized ions in the gas cell are guided and extracted to a vacuum environment by a combination of de electric fields and inhomogeneous rf fields (rf carpet ion guide). From there the slow ion beam is delivered via a mass separator and a switchyard to various devices: such as an ion trap, a collinear fast beam apparatus, and a multi-reflection time of flight mass spectrometer. In the R&D works at the present RIKEN facility, an overall efficiency of 5% for a 100A MeV 8Li ion beam from the present projectile fragment separator RIPS was achieved and the dependence of the efficiency on the ion beam intensity was investigated. Recently our first spectroscopy experiment at the prototype SLOWI was performed on Be isotopes. Energetic ions of 10Be and 7Be from the RIPS were trapped and laser cooled in a linear rf trap and the specific mass shifts of these isotopes were measured for the first time.

A large segmented neutron detector for reaction studies with radioactive beams near the Coulomb barrier

A large, segmented neutron detector array, the “neutron wall”, has been constructed for use with the TwinSol radioactive nuclear beam facility at the University of Notre Dame. At present, the array consists of 16 position-sensitive plastic scintillator bars. The position and energy resolution of the array, and its neutron-detection efficiency are described.

Beta-decay rates

Major astrophysical applications involve a huge number of exotic nuclei. Their beta-decay properties play a crucial role in stellar explosive events. An important effort has been developed in last decades to measure the masses and β-decay properties of very neutron-rich nuclei at radioactive nuclear beam facilities. However, most of them cannot be synthesized in terrestrial laboratories and only theoretical predictions can fill the gap. We will concentrate mainly on the β-decay rates needed for stellar r-process modeling and for performing the RNB experiments. An overview of the microscopic approaches to the β-decay strength function is given. The continuum QRPA approach based on the self-consistent ground state description in the framework of the density functional theory is outlined. For the first time, a systematic study of the total β-decay half-lives and delayed neutron emission probabilities takes into account the Gamow–Teller and first-forbidden transitions. Due to the shell configuration effects, the first-forbidden decays have a strong impact on the β-decay characteristics of the r-process relevant nuclei at Z ≈ 28 , N > 50 ; Z ⩾ 50 , N > 82 and Z = 60 – 70 , N ≈ 126 . Suppression of the delayed neutron emission probability is found in nuclei with the neutron excess bigger than one major shell. The effect originates from the high-energy first-forbidden transitions to the states outside the ( Q β − B n ) -window in the daughter nuclei. The performance of existing global models for the nuclides near the r-process paths is critically analyzed and confronted with the recent RIB experiments in the regions of 78Ni, 132Sn and “east” of 208Pb.

8Li and 18F diffusion experiments in solids - an application of accelerated RNB -

An ISOL based radioactive nuclear beam (RNB) facility in Japan, TRIAC (Tokai Radioactive Ion Accelerator Complex), will be able to provide various short-lived radioactive isotopes for experiments with an energy ranging from 0.1 to 1.1 MeV/nucleon. As an interdisciplinary application of the RNB for materials science, two experiments have been proposed; diffusion studies in super ionic conductors, and β-NMR and PAC studies by implantation of polarized RNB. The present status of the experimental and instrumental development for the experiments is discussed.

Facilities and Methods: KEK-Jaeri Joint RNB Facility, TRIAC

Research and development on an isotope separator on-line (ISOL)-based radioactive nuclear beam (RNB) facility in Japan had mainly been carried out at the Institute for Nuclear Study (INS), University of Tokyo [1]. The first RNB acceleration was realized with the split-coaxial RFQ (SCRFQ) and interdigital-H (IH) type linacs in March 1997. A joint RNB facility, TRIAC (Tokai Radioactive Ion Accelerator Complex) facility, is partly based on the re-installation of the above INS-facility in Tokai site of the Japan Atomic Energy Research Institute (JAERI). It will open up the RNB science with 1.1 MeV/u RNBs from FY2005. The higher energetic (5-8 MeV/u) RNBs will be available in the near future.

RNB Facilities in Europe - Present and Future

A brief overview is given of present and future radioactive nuclear beam (RNB) facilities in Europe. Recent developments and extensions of RNB schemes and their uses are mentioned. The two major facilities planned for Europe employing, respectively, the in-flight and ISOL schemes are briefly presented.

Giant resonance research: present interests and future perspectives

In the last decade extensive work has been done to explore and understand various giant resonance phenomena. The research involved the study of the giant dipole resonance as a function of temperature and angular momentum, the study of compressional modes - the isoscalar giant monopole and dipole resonances - and the investigation of their microscopic structures, the study of the charge-exchange modes both in the β + and β − directions, the establishment of the existence of double-phonon giant resonances, in particular those of the isovector GDR and the isoscalar GQR, etc.. A review of some of these advances is discussed and possible future directions in view of the operating and/or planned radioactive nuclear beam facilities will be delineated.

Giant resonance research: present interests and future perspectives

In the last decade extensive work has been done to explore and understand various giant resonance phenomena. The research involved the study of the giant dipole resonance as a function of temperature and angular momentum, the study of compressional modes - the isoscalar giant monopole and dipole resonances - and the investigation of their microscopic structures, the study of the charge-exchange modes both in the β + and β − directions, the establishment of the existence of double-phonon giant resonances, in particular those of the isovector GDR and the isoscalar GQR, etc.. A review of some of these advances is discussed and possible future directions in view of the operating and/or planned radioactive nuclear beam facilities will be delineated.

Giant resonance research: present interests and future perspectives

In the last decade extensive work has been done to explore and understand various giant resonance phenomena. The research involved the study of the giant dipole resonance as a function of temperature and angular momentum, the study of compressional modes - the isoscalar giant monopole and dipole resonances - and the investigation of their microscopic structures, the study of the charge-exchange modes both in the β + and β − directions, the establishment of the existence of double-phonon giant resonances, in particular those of the isovector GDR and the isoscalar GQR, etc.. A review of some of these advances is discussed and possible future directions in view of the operating and/or planned radioactive nuclear beam facilities will be delineated.

The KEK–JAERI joint RNB project

A new ISOL-based radioactive nuclear beam (RNB) facility has been constructed as a joint project of the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institute (JAERI) at the Tandem accelerator of the Tokai site of JAERI. It uses heavy-ion linacs and related equipment of the presently closed KEK-RNB facility. Fission fragments with energy from 0.1 to 8 MeV/u will be available at this facility.

Status of the EURISOL project

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.

The development of an ECR charge breeder for KEK-JAERI joint RNB project

For the construction of an electron cyclotron resonance (ECR) charge breeder (CB) at KEK-JAERI radioactive nuclear beam facility, we have made a pilot charge breeding system consisting of two compact-sized ECR ion sources. In order to find the necessary conditions for an ECRCB with high efficiency, the charge breeding efficiency for Ar ions in nitrogen plasma has been measured and compared with the results from the simulation of the trajectories of the ions in the plasma. By explicitly taking into account the cumulative small angle scattering of charged ions as well as the confinement magnetic field of the pilot CB, the simulation predicts the stopping efficiency. This is defined as a probability that the injected ions are still within the plasma volume when their initial directional motions have become randomized. Incorporating the ionization efficiency for the ions, the overall breeding efficiency has been estimated. Finally, the characteristics of the ECRCB recently installed for tests at KEK is described.

Current progress of nuclear astrophysics study and BRNBF at CIAE

A secondary beam line (GIRAFFE) at the Beijing tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, we have carried out measurement of 7Be(d,n) 8B, 11C(d,n) 12N, 8Li(d,n) 9Be and 6He(p,n) 6Li reactions. The proposed Beijing radioactive nuclear beam facility and its current R&D progress are briefly introduced. This facility is based on the exist HI-13 tandem accelerator. A proton cyclotron will be built to provide 100 MeV 200 μA proton beam, together with an isotope separator on line system and a super-conducting heavy ion LINAC. By this facility, intensity of order of 10 9 pps radioactive nuclear beams for mass up to A=120 will be produced.