Author: Murphy, R.C.
Paper Title Page
TUP046 Superconducting 72 MHz β=0.077 Quarter-wave Cavity for ATLAS 892
 
  • M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid
    ANL, Argonne, USA
 
  A 72 MHz superconducting (SC) niobium quarter-wave cavity (QWR) optimized for β=0.077 has been built and tested as part of a beam intensity upgrade of the ATLAS SC heavy-ion linac. The two-gap cavity, designed to accelerate ions over the velocity range 0.06<β<0.12 and provide 2.5 MV of accelerating voltage per cavity at T=4.5 Kelvin, is based on a highly optimized electromagnetic design to reduce surface electric and magnetic fields. Horizontal electropolishing on the complete cavity with the helium jacket, is similar to that performed on 1.3 GHz ILC-type cavities and is a first for a low-β TEM cavity. This development is part of a broader effort to demonstrate ~120 mT surface fields with Rs~5 nΩ in 2 K operation for low-β cavities with the aim of substantially reducing the footprint for future ion linacs. First rf cold test results show the highest accelerating gradients (13.4 MV/m, leff=βλ) and voltage/cavity (4.3 MV) achieved for this class of SC cavity.