BNL, Upton, Long Island, New York
A prototype ampere-class superconducting energy recovery linac (ERL) is under advanced construction at BNL. Its motivation, design, special features and status will be described. The Collider-Accelerator Department at BNL, which operates RHIC, is planning an electron-ion collider called eRHIC. The eRHIC electron beam will be provided by a multi-pass superconducting ERL. At the highest energy and luminosity, eRHIC will have 5 passes at 260 mA, whereas an intermediate version of eRHIC (called MeRHIC) will have 3 passes at 50 mA. To test the feasibility of such an ampere-class ERL we are constructing a prototype ERL designed to operate at up to 500 mA average current. The BNL R&D ERL will serve as a test bed for eRHIC. It will operate at 703.75 MHz. Its special features are an SRF laser photocathode RF gun designed to deliver 2 MeV at 500 mA, a high QE multi-alkaline cathode preparation and load-lock system, an emittance-preserving merging system, and a highly damped 5-cell 20 MeV ERL cavity. Tests at the ERL will include high-current handling, coherent emissions, and emittance performance. The ERL will also serve as a platform to study HOM damping issues.
BNL, Upton, Long Island, New York
The development of Higher Order Mode dampers for a five-cell cavity is being persued at this laboratory. The physics needs and technical requirements for several future electron-ion collider projects are under study, which all involve Energy Recovery Linacs. The envisioned Ampere class currents make effective HOM damping mandatory which will be achieved with capacitive probes and inductive loops. Longitudinal space requirements constrain the space between the cavities in the linac chain. Two five-cell copper cavities are assembled with minimal separation to simulate the space available for fundamental power coupler, beam position pickup probe, and two HOM dampers. The location of the dampers is chosen in the connecting beam tubes to balance fundamental mode suppression and HOM damping. Measured and simulated Cu cavity results are compared with those for the ferrite-damped superconducting ERL.