• 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.