THE JLAB AMPERE-CLASS CRYOMODULE CONCEPTUAL DESIGN

For the next generation of compact high-power FELs a new cryomodule is required that is capable of accelerating up to Ampere levels of beam current. Challenges include strong HOM damping, high HOM power and high fundamental-mode power (in operating scenarios without full energy recovery). For efficient use of space a high real-estate gradient is desirable and for economic operation good fundamental-mode efficiency is important. The technology must also be robust and should be based on well-proven and reliable technologies. For Ampere-class levels of beam current both halo interception and beam break-up (BBU) are important considerations. These factors tend to drive the designs to lower frequencies where the apertures are larger and the transverse impedances are lower. To achieve these goals we propose to use a compact waveguide-damped multicell cavity packaged in an SNS-style cryomodule. CONCEPT Future high-power FEL’s for scientific, defense or industrial applications could benefit from a compact, economical and efficient accelerator layout. A small but powerful energy recovered linac (ERL) with a single high-current cryomodule could meet those requirements. The parameters for such a module are listed in table 1 and can be met using six strongly HOM damped multi-cell cavities, figure 1, in a stretched SNS-style cryomodule [1]. Experience with the JLab 10 kW FEL suggests that operating with less than 100% energy recovery is sometimes necessary so the linac cryomodule must be capable of supplying significant power to the beam.