The effect of nitrogen infusion on a 162.5 MHz low beta superconducting HWR cavity

Abstract Nitrogen doping or nitrogen infusion is new technology that has been recently developed to improve the quality factor of superconducting RF (SRF) cavities. The technique favors higher frequency 2K applications (especially for frequencies higher than 1 GHz). In this paper nitrogen infusion has been applied to a β = 0 . 09 162.5MHz high current superconducting half wave resonator (HWR) with a relatively large beam pipe which has been developed at Peking University for the deuteron driver accelerator of the Beijing Isotope-Separation-On-Line neutron rich beam facility (BISOL). The cavity demonstrated an increase in the quality factor Q 0 at both 4.2 K and 2.0 K, the value of Q 0 was increased by about 60% at a very low field at 4.2 K and Q 0 doubled at the accelerating gradient of E acc = 10 MV/m and at 2.0 K. The HWR cavity performance both with and without nitrogen infusion surface treatment has been presented in this paper.