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.
PKU/IHIP, Beijing
DC-SC photocathode injector was upgraded for Peking University Free Electron Laser (PKU-FEL) facility. A 3.5-cell superconducting cavity is the key component of the DC-SC photoinjector. Design and simulation of the 3.5-cell cavity was finished. Two 3.5-cell SRF cavities was fabricated at Peking University. One is made of large grain niobium and the other is made of fine grain niobium. All the material are from Ningxia OTIC. After BCP treatment and 1250 C post purification by Peking University, the 3.5-cell LG cavity was sent to Jlab for test. Due to the special structure , the cavity was treated with BCP, 800 C degassing and HPR at Jlab. The Eacc of the cavity reached 23 MV/m with Q=1.2·1010 at highest gradient. The 3.5-cell LG Nb cavity was installed to the new DC-SC photoinjector and will be tested with the cryomodule for the next step.
