The issues in the development of a f=162.5 MHz, β=0.12 superconducting half-wave resonator for the Rare Isotope Science Project (RISP)

A f=162.5 MHz superconducting half-wave resonator (HWR) with β=0.12 is one of the four superconducting cavities being developed for the heavy ion linac of the Rare Isotope Science Project (RISP). The linac will accelerate various ions ranging from proton to uranium with beam power of about 400 kW. In particular, the HWR's will accelerate the ion beam in low-medium energy range, i.e., from 1.6 to 18 MeV for the case of uranium. In this paper, we describe design, fabrication, surface treatment, and vertical test of the 1st prototype of the cavity in detail. We also discuss some issues on the performance enhancement of the cavity. The Q0 values at 2 K surpassed the target performance, Q0=1.1×109 at Eacc=6.3MV∕m.