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.
