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

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.