• V. Parma, S. Calatroni, N. Delruelle, J. Hansen, C. Maglioni, M. Modena, M. Pasini, T. Trilhe
  CERN, Geneva
• S.M. Pattalwar
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The High Intensity and Energy (HIE) proposal plans a major upgrade of the existing ISOLDE and REX-ISOLDE facilities at CERN, with the objective of substantially increasing the energy and the intensity of the delivered radioactive ion beams. In the frame of this upgrade activity, a superconducting linac, based on Nb sputtered Quarter Wave Resonators (QWRs) is proposed to be installed downstream of the present normal conducting machine. The present design of the accelerator lattice features housing of five high-beta cavities (β=10.6%) and a superconducting solenoid in a common cryomodule. In most of the existing low-energy heavy-ion installations worldwide, insulation and beam vacuum are in common, with the risk of cavity surface contamination in case of accidental leak to the cryostat vessel. Following a concept study, we report in this paper on three design options, namely cryomodules with common vacuum, with separate or with hybrid vacuum systems (the latter having a low conductance between insulation and beam vacuum) and compare them in terms of technical complexity, performance, reliability and maintainability.

• M.A. Drury, E. Daly, G.K. Davis, J.F. Fischer, C. Grenoble, J. Hogan, F. Humphry, L.K. King, J.P. Preble, K. Worland
  JLAB, Newport News, Virginia

Funding: Authored by JSA, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The Thomas Jefferson National Accelerator Facility is currently engaged in a cryomodule refurbishment project. The goal of this project is robust 6 GeV, 5 pass operation of the Continuous Electron Beam Accelerator Facility (CEBAF). The scope of the project includes removing, refurbishing and replacing ten CEBAF cryomodules at a rate of three per year. Refurbishment includes reprocessing of SRF cavities to eliminate field emission and increase the nominal gradient from the original 5 MV/m to 12.5 MV/m. New 'dogleg' couplers between the cavity and helium vessel flanges will intercept secondary electrons that produce arcing at the 2 K ceramic window in the Fundamental Power Coupler (FPC). Modification of the Qext of the FPC will allow higher gradient operations. Other changes include new ceramic rf windows for the air to vacuum interface of the FPC and improvements to the mechanical tuners. Any damaged or worn components will be replaced as well. Currently, five refurbished cryomodules have been installed in CEBAF. These cryomodules have been installed in CEBAF and are currently operational. This paper will summarize the test results and current operational experience.