The nuclear shell model towards the drip lines

Presented are features of the in-flight radioactive isotope (RI) beam separators in Japan as well as of a next-generation separator BigRIPS being built at RIKEN for the RI-beam factory project. Characteristic features and present status of the existing separators are reviewed for the RIPS at RIKEN, the Secondary Beam Line at RCNP, the Secondary Beam Course at NIRS, the CRIB at CNS and the RMS at JAERI. Design features are outlined for the BigRIPS, which is characterized by two major features: large acceptances and a tandem (or two-stage) separator scheme. The large acceptances allow one to produce RI beams efficiently by using in-flight fission of uranium ions, being achieved by using superconducting quadrupoles with a large aperture. The tandem separator scheme allows one to deliver tagged RI beam. The integrated capability of the BigRIPS and the accelerators of the project can significantly enlarge the scope of future RI-beam experiments. A low-energy course following the BigRIPS can provide energy-degraded and -bunched RI beams to be applied for a gas catcher system with an RF ion guide, aiming at realizing a projectile fragmentation based ISOL system.

In-flight RI beam separator BigRIPS at RIKEN and elsewhere in Japan

Nuclear structure at the proton drip line: Advances with nuclear decay studies

Nuclear Data Sheets for A = 24

Nuclear Data Sheets for A = 98

A novel experimental approach has been employed for the measurement of $\ensuremath{\beta}$-delayed protons from ${}^{24}\mathrm{Si}$ produced via the fragmentation of a ${}^{28}\mathrm{Si}$ beam with an energy of 100 MeV/nucleon. The secondary beam of ${}^{24}\mathrm{Si}$ was separated by the projectile fragment separator RIPS at RIKEN and was implanted in a 2.6 $\ensuremath{\mu}\mathrm{m}$ aluminum foil placed parallel to a gas-$\ensuremath{\Delta}E$ and silicon-$E$ detector telescope for the measurement of delayed protons. The above arrangement has led to a very clean, $\ensuremath{\beta}$-ray background free delayed proton energy spectra and a few new proton peaks could be identified from the decay of ${}^{24}\mathrm{Si}.$

β-delayed proton decay of 24 Si

The Radioactive Ion Beam (RIB) facility, now under construction at the Variable Energy Cyclotron Centre (VECC), Kolkata, is based on the use of the well-known Isotope Separator On-Line (ISOL) technique in which the radioactive nuclei are produced by nuclear reactions with the primary beam in selected thick targets. The present article deals with the various aspects of a thick target design for the production of RIB using compound nuclear reactions with proton and alpha particle beams from the VEC cyclotron. The design involves, to start with, an optimum choice of the target compounds necessary for the production of various RIBs of interest, which satisfy a number of selection criteria. The requirements that a target should be mechanically stable, highly permeable and has a short diffusion length for radioactive atoms, limit the choice of target forms to a few. In our design, we have worked out in detail the prospect of using fibrous and composite targets like carbon fiber as backing matrix for deposition of several selected target compounds. The performance of the composite target system has been tested in beam.

Preparation and optimization of targets for the production of radioactive ions at VECC

Recently an experiment has been carried out at RIKEN, Japan, using the projectile fragment separator RIPS to test a new approach of studying -delayed proton emitters. The approach consists of reduction of contamination from neighbouring isotones and isotopes by using a set of Al absorbers at the RIPS focal plane and stopping the fragments of interest on a thin foil placed in front of a gas -Si E detector telescope for delayed proton measurement. These two together have led to a remarkable reduction of -background in the delayed proton spectrum of and a number of new levels in decaying by proton emission to have been observed. The details of the technique and the results obtained from the -delayed proton decay of will be discussed.

http://iopscience.iop.org/article/10.1088/0954-3899/24/8/014/pdf

Beta-delayed proton spectroscopy of

β-delayed proton decay of 24Si

A radio frequency quadrupole LINAC has been designed for the VECC-RIB project for an input beam energy of 1.0 keV/u and q/A≥1/16. The output energy will be about 90 keV/u for a 3.4 m long, 35 MHz structure. A half-scale cold model of the RFQ has been fabricated and tested for rf structure design study. The beam dynamics and rf-structure design along with the results of the cold model tests will be presented.

V. Banerjee

Papers

β-delayed proton decay of 24 Si

Preparation and optimization of targets for the production of radioactive ions at VECC

Beta-delayed proton spectroscopy of

β-delayed proton decay of 24Si

The design of a radio frequency quadrupole LINAC for the RIB project at VECC Kolkata