Performance of bialkali photocathode in DC-SRF photoinjector

Abstract

To obtain a low emittance, high current electron beam, a bialkali photocathode (K-Cs-Sb) was adopted in an upgraded DC-SRF photoinjector at Peking University. Based on the design and manufacture of the preparation and transport systems, a study of the K-Cs-Sb photocathode deposition and an electron beam performance test was carried out. The main improvement in the recipe is to reduce the cesiation process from ∼50 min to ∼6 min, and the lifetime of K-Cs-Sb photocathode can be increased, obviously, while the QE remains the same. During a performance test with a beam, a degradation in QE was found at 36 K, which is the lowest temperature for the operation of K-Cs-Sb photocathode in gun to date. However, the QE of K-Cs-Sb photocathode still exceeds 0.3% and can deliver an electron beam with a bunch charge of ∼150 pC and a repetition rate of 1 MHz. This QE is higher than reported at cryogenic temperature for SRF electron guns.