Investigation of Superconducting Niobium Cavities at S-Band

Abstract
This paper describes the investigation of superconducting Nb cavities at S-band frequencies. The TE 011 and TM 011 cavities were machined by Varian Associates from solid billets of electron-beam-melted niobium and chemically polished to remove all work-damaged material. At low power levels, the TE 011 cavity had a measured Q o (4.2°K) 324 × 10 6 and a residual Qres ≈ 6.97 × 10 9 , whereas the TM 011 cavity had a Q o (4.2°K) ≈ 89 × 10 6 and a residual Q res ≃ 425 × 10 6 . These results correspond to a surface resistance of R(4.2°K)/f 2 = 0.29 μΩ/GHz 2 . High level measurements were limited at a critical RF field H ac c = 15.5 G in the TM 011 mode and H ac c = 290 G in the TE 011 mode.