• W. Hartung, S. Bricker, C. Compton, K. Elliott, M. Hodek, J.P. Holzbauer, M.J. Johnson, O.K. Kester, F. Marti, S.J. Miller, D. Norton, J. Popielarski, L. Popielarski, J. Wlodarczak, R.C. York
  NSCL, East Lansing, Michigan
• A. Facco
  INFN/LNL, Legnaro (PD)
• E.N. Zaplatin
  FZJ, Jülich

Niobium quarter-wave resonators (QWRs) and half-wave resonators (HWRs) are being developed at Michigan State University for two projects: a 3 MeV per nucleon superconducting linac for re-acceleration of exotic ions (ReA3, under construction, requiring 15 resonators), and a 200 MeV per nucleon driver linac for the Facility for Rare Isotope Beams (FRIB, under design, requiring 344 resonators). The QWRs (80.5 MHz, optimum beta = 0.041 and 0.085) are required for both ReA3 and FRIB. Both include stiffening elements and frictional dampers. Nine beta = 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 beta = 0.085 QWRs is in progress. The HWRs (322 MHz, optimum beta = 0.29 and 0.53, required for FRIB) are designed for mechanical stiffness and low peak surface magnetic field. A prototype beta = 0.53 HWR has been fabricated, and a prototype beta = 0.29 HWR is planned. This paper will cover the RF and mechanical requirements, the resonator and vessel design, and Dewar testing of production resonators.