Jefferson Lab IR FEL cryomodule modifications and test results

The Infrared Free Electron Laser being constructed at the Thomas Jefferson National Accelerator Facility will require a 42 MeV, 5 mA electron accelerator. The accelerator design requires a 10 MeV injector and a two pass 32 MeV linac, one pass for acceleration and one pass for energy recovery. In order to minimize the cost of the linac, standard CEBAF 1497 MHz superconducting RF cavities and cryomodules are being used with minimal changes. Two SRF cavities, housed in a quarter cryomodule, operate at a nominal 10 MV/m to provide the injector energy. The linac is composed of one cryomodule, housing eight SRF cavities operating at an average gradient of 8 MV/m. The modifications to the cryomodule are being made to handle the higher beam current, to improve RF control, and to increase machine reliability. The modifications to the higher order mode (HOM) loads, cavity tuners, cavity beam line, warm and cold RF windows, and cryogenic shield are described. Test results from the injector quarter cryomodule are also presented