INVESTIGATION OF SUPERCONDUCTING NIOBIUM CAVITIES AT S-BAND

This paper describes the investigation of superconducting Nb cavities at S-band frequencies. The TE011and TM011cavities 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 TE011 cavity had a measured Q0(4.2°K) e~324 × 106 and a residual Qres~ 6.97 × 109, whereas the TM011cavity had a Q0(4.2°K) ~ 89 × 106 and a residual Qres=-425×106. These results correspond to a surface resistance of R(4.2°K)/f2= 0.29 µΩ/GHz2, High level measurements were limited at a critical RF field Hcac= 15.5 G in the TM011mode and Hcac= 290 G in the TE011mode. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.