Design study of superconducting quarter wave resonator for post acceleration of radioactive Ion beam facility at VECC, Kolkata

A Superconducting (SC) resonator (QWR) designed to operate at 113.6 MHz with geometry beta of 0.055 is under development for the post-acceleration of Rare Isotope Beam (RIB) at VECC, Kolkata. The QWR section of the post accelerator is composed of two cryostat module each containing four hermetically sealed QWRs having separate vacuum from cryostat. Each QWR module will accelerate beam up to q/A=1/7 with accelerating gradient of 5.0 MV/m in CW mode. In this paper, the design of the QWR has been reported considering issues like sufficient operational margin, beam dynamical requirements, mechanical fabrication, etc. The simulations performed with FEM code show that the tuning system can adjust and compensate the frequency drift due to external vibrations and helium pressure fluctuation during operation. In order to minimize the undesirable beam steering effect due to vertical component of electric field, studies has been made to optimally position QWRs inside cryostat.