Optimization of single spoke resonator (SSR) cavities for the MEHIPA LINAC

The second stage of the Indian ADS programme envisages building a high current, 200 MeV superconducting proton accelerator: the Medium Energy High Intensity Proton Accelerator (MEHIPA). The MEHIPA Reference Design Report (RDR) studies a 10 mA, 200 MeV linac, consisting of a 3 MeV normal conducting RFQ followed by three families of superconducting Single Spoke Resonators (SSRs). Single spoke structures are well known for their excellent RF performance in the low to middle beta range as well as for their excellent mechanical stability. The three SSR families for the MEHIPA linac are named SSR-A, SSR-B and SSR-C, designed to accelerate from 3-10 MeV, 10-50 MeV and 50-200 MeV respectively, with geometri β of 0.11, 0.21 and 0.46 respectively. Here we present detailed optimization studies for the geometric β followed by their RF design. The relevant geometric parameters obtained from the sensitivity analysis of these cavities are used to minimize the Epeak/Eacc and Bpeak/Eacc ratios while keeping a high value for the shunt impudence. The cavity designed goals were achieved with peak surface fields below 40 MV/m and 70 mT. (author)