SUPERCONDUCTING COAXIAL RESONATOR DEVELOPMENT FOR ION LINACS AT MICHIGAN STATE UNIVERSITY

Niobium quarter-wave resonators (QWRs) and halfwave resonators (HWRs) are being developed at Michigan State University (MSU) for two projects: a 3 MeV per nucleon (MeV/u) superconducting linac for re-acceleration of exotic ions (ReA3, under construction, requiring 15 resonators), and a 200 MeV/u driver linac for the Facility for Rare Isotope Beams (FRIB, under design, requiring 344 resonators). The QWRs (80.5 MHz, optimum β = v/c = 0.041 and 0.085) are required for both ReA3 and FRIB. Both QWRs include stiffening elements and frictional dampers. Nine β = 0.041 QWRs have been fabricated; seven of them have been Dewar tested successfully with a helium vessel for use in ReA3. Production and testing of ten β = 0.085 QWRs is in progress. The HWRs (322 MHz, optimum β = 0.29 and 0.53) are required for FRIB, but not ReA3. Both HWRs are designed for mechanical stiffness and low peak surface magnetic field. A prototype β = 0.53 HWR has been fabricated and tested, and a prototype β = 0.29 HWR is planned.