RA1. RIB Development
(D. W. Stracener)
In the last few months, a number of on-line and off-line tests have been performed at the On-Line Test Facility (OLTF) and at the High Power Target Laboratory (HPTL). In addition, a new target and ion source (TIS) assembly station is near completion.
The current assembly station has the capability for assembling and testing TIS modules for the IRIS-1 (Injector for Radioactive Ion Species 1) production platform. At the new assembly station we will be able to fully assemble and test TIS assemblies for both RIB production platforms. The TIS module tests include alignment of the utility connections (cooling water, electrical, vacuum, thermocouples, pressure gauges, and gas feeds), check for vacuum and water leaks, alignment of the RIB production target, check of the electrical connections in the ion source, and a high temperature test of all systems. The high temperature test also helps to outgas the target and ion source before it is moved to the production platform.
At the OLTF, targets are tested using low-intensity beams from the tandem accelerator. Proton and deuteron beam intensity is limited to less than 50 nA with energies up 40 MeV. A uranium boride target was irradiated with 40-MeV protons to look for the release of zirconium isotopes as molecular boride ions. After several on-line tests and an irradiation and release measurement, it appears that zirconium has very low release efficiency from uranium carbide or uranium boride targets. Andreas Kronenberg (ORAU) has been the principal investigator for this series of tests. In collaboration with Will Talbert (TechSource), Jerry Nolen (ANL), and John Greene (ANL), we recently tested a very high density (10.5 g/cm3) uranium carbide target. Using 40 MeV protons to induce fission, we measured the beam yields for a large number of fission fragments. The preliminary analysis indicates lower release efficiencies than are observed for lower density targets. The details of this analysis will be presented later. Experiments can also be made using heavy-ion beams from the tandem. A recent experiment to investigate targets for the production of beams in the region of Ag-97 used a Ni-58 beam on a Cr target. Chris Goodin (Vanderbilt) is the principal investigator for these experiments.
At the HPTL, targets are tested using light-ion beams from the cyclotron. Using 54-MeV and 42-MeV proton beams with intensities up to 15 μA, we have measured the yields of Al-25 and Al-26m beams from various silicon carbide (SiC) targets. A series of tests using SiC fiber targets (15 micron diameter fibers) have shown limited release of short-lived aluminum isotopes and the targets suffer significant damage when the production beam current exceeds 7 μA. In collaboration with Alberto Andrighetto and coworkers from Legnaro, we recently tested a SiC target design that allows higher production beam currents. The SiC disks are about 1.2 mm thick and separated by about 4 mm to allow for faster heat dissipation via radiation to the walls of the target chamber. So far there is no indication of target damage up to 12 μA and the normalized yields for aluminum isotopes are comparable to those observed with the SiC fiber targets. The Legnaro group has developed a detailed model to simulate temperatures in the target and these simulations agree quite well with the observed target temperatures. The HPTL is presently off-line to allow for the installation of the IRIS-2 platform and high voltage conduits. We plan to resume the on-line development of SiC targets later this year.