Thermal emittance measurements of a bi-alkali photocathode based on the high voltage DC photogun beamline

Abstract At the SRF Laboratory of Peking University, we utilized the -100 kV high-voltage DC photogun to employ the solenoid scan method for measuring the thermal emittance of CsK 2 Sb photocathode. Various laser wavelengths were employed at very low currents, leading to a negligible space charge effect. Additionally, we conducted measurements of the CsK 2 Sb photocathode's thermal emittance at a wavelength of 520 nm under different high voltages, (HV), establishing that the Schottky effect caused by the high voltage essentially unaffected the thermal emittance in the range of 50 kV ∼ 100 kV.