Assembling experience of the first two HIE-ISOLDE cryomodules

The assembly of the first two cryomodules (CM1 and CM2) of the new superconducting linear accelerator HIE-ISOLDE (High Intensity and Energy ISOLDE), located downstream of the REX-ISOLDE normal conducting accelerator, started one year and half ago. After a delicate assembly phase in the cleanroom which lasted nine months, the first cryomodule was transported to the ISOLDE hall on 2 May 2015 and coupled to the existing REX-ISOLDE accelerator, increasing the energy of the radioactive ion beams from 2.8 to 4.3 MeV per nucleon. The superconducting linac supplied the CERN-ISOLDE Facility, with radioactive zinc ions until the end of the proton run in November 2015. At the beginning of 2016, the second cryomodule was installed in the machine, increasing the energy to 5.5 MeV per nucleon. During commissioning of the first cryomodule in summer 2015, it was found that the performance of the RF superconductive cavities was limited by the over-heating of their RF couplers. The decision was taken to refurbish CM1 and reinstall it at the end of April. In this paper, we present the challenges faced and the experience gained with the cleanroom assembly of the first two cryomodules, especially the construction of the SC RF cavities and their RF ancillaries.