Cs-Te photocathode RF electron gun for applied research at the Waseda University

A compact electron accelerator based on photo-cathode RF electron gun is under development for applied research at the Waseda University. Higher charge and higher energy are key issues for applications such as pulse radiolysis experiment and laser-Compton X-ray generation. The new RF-gun cavity with cesium telluride (Cs-Te) photo-cathode which has higher quantum efficiency (Q.E.) compared with metal cathodes has been installed. The evaluation of Q.E. of the photo-cathode has been performed and the value obtained is more than 5% at the preparation stage. For understanding the Cs-Te cathode properties and the higher Q.E. operation, fundamental studies by single bunch beam operation have been performed resulting in more than 6 nC bunch charge with a high Q.E. of 2.9%. Additionally, the new RF-gun cavity was improved for obtaining a higher Q value. Higher beam energy, i.e. shunt impedance compared with old type cavity, was observed. The shunt impedance increased by about 20%. These successful results will considerably contribute to the applied research.