SUPERCONDUCTING Nb TM010 MODE ELECTRON-BEAM WELDED CAVITIES

Several superconducting TM010 mode Nb cavities at 8.6 GHz with high measured unloaded Q's and fields were made using commercial reactor-grade Nb, practical fabrication techniques, and practical processing techniques. The cavities were fabricated by machining the cavities in two parts from a solid billet of Nb and then joining the two parts with electron-beam welding. The cavities were processed primarily by using ultra-high-vacuum firing (1750–2100 °C) and chemical polishing. Unloaded Q's as high as 1011 were measured at low field levels, and surface fields as high as 1080 Oe and 70 MV/m were obtained with unloaded Q's on the order of 1010.