At the Compact-ERL (cERL) at KEK, installation of the electron gun, superconducting cavity, and other components began in 2012, with the first beam recirculation operation achieved in 2013 and energy-recovery operation of a 1 mA CW beam in 2016.
A photocathode DC electron gun was employed, and development progressed with two systems. I have been involved in the development of these electron guns from the beginning, and have participated in their construction and operation.
I will introduce the development of these electron guns and various issues, including operational problems, especially the points that are unique to these guns and important in terms of performance.
Then I will present some examples of the operation and adjustment of the cERL electron gun and injector, and finally I will describe the state of preparation for the 10 mA CW beam operation that we are currently trying to achieve.
