This contribution describes the latest milestones of a multiyear program to build and operate a compact -300 kV dc high voltage photogun with inverted insulator geometry and alkali-antimonide photocathodes. Photocathode thermal emittance measurements and quantum efficiency charge lifetime measurements at average current up to 4. 5 mA are presented. as well as an innovative implementat... https://www.ngetikin.com/