Highly Pervious Liquid Metal Target Systems for Radioactive Ion Beam Generation

摘要

Radioactive ion beams (RIBs) of (69)As are currently needed for fundamental nuclear physics research and can be produced abundantly by proton bombardment of a liquid Ge target. In this thesis, we develop a series of highly pervious liquid target designs with mean diffusion paths several orders of magnitude less than traditional, pool-type, liquid targets. Experiments have been performed to identify materials (substrates) capable of suspending, through wetting, very thin layers of liquid Ge. Four candidate Ge-substrate target systems have been designed, and (69)As production may be significantly increased over previous targets. The target systems designed include liquid Ge coated onto an: (1) inclined W plane, (2) a long thin Mo wire birdsnest, (3) a SiC weave, and (4) SiC coated C foam. A universal Ta target holder coupling the target to an ion source has also been designed and features a cooled re-circulating baffle for testing of each of the above target concepts. The results of long-term heating tests on the Mo wire birdsnest show its lifetime to be less than 100 hours; however, future online tests of short duration will test (69)As production for the birdsnested target. Ge did not wet the SiC weave target. The methods and design formulations developed in this thesis are applicable to a variety of RIB species produced from liquid targets.