ATF 120 Hz Photocathode RF Gun Injection System Design Studies X.J. Wang, X.Y. Chang S. Pjerov and M. Woodle National Synchrotron Light Source Brookhaven National Laboratory Upton, NY 11973

Outline This is a research in progress with zero funding, we are making progress: Design philosophy. Thermal simulation of photocathode RF gun. Mechanical design and modification. Vacuum studies Ultra-stable high repetition photocathoder RF gun drive laser system. Beam dynamics studies. Front end optics. Electron beam diagnostics. Emittance compensation magnets improvement.

Design philosophy Based on the BNL GUN IV design, improve both the cooling capabilities and performance. It will be a systematic approach, we will examine all components’ performance for 120 Hz operation, including 1. Photocathode RF gun 2. Emittance compensation solenoid magnet, 3. Beam diagnostics, 4. High- repetition rate RF gun driving laser system. 5. Front-end Laser beam optics 6. Beam dynamics. 7. Linac for energy up to 70 MeV.

BNL Photocathode RF Gun IV Injection System Photocathode RF gun injections system consists of: 1. RF Gun. 2. Solenoid Magnet. 3. Beam diagnostics. Operating in many labs, it is capable of operating at 50 Hz with 4 us flat top RF pulse.

RF gun We have made following decisions: 120 Hz operation at gun body operating temperature at 15 C. The operating vacuum with RF on will be better than 5x10-10 torr. Dark current reduction will be the priority, this will including material selection and its processing technique. Add cooling channel on the waveguide. Increase the water channel size around the disk, and move it location close to the inner surface. Improve the Mg cathode mount, we need to look into the laser heating.

BNL 120 Hz RF Gun

Solenoid Magnet Improve the RF gun mount on the solenoid to insure the electrical center of the gun co-linear with the magnet center of the solenoid magnet. Improve the thermal isolation between the RF gun and solenoid magnet, this will improve the thermal stability of the gun, and easy bake out of the gun. Improve the survey target. We are considering shaping the pole shape to provide more focusing. We need 1 month engineering, 2 to 3 months design support so we can finish all mechanical design of the RF gun and solenoid magnet.

Beam Dynamics Studies We have proposed, and experimentally demonstrated bunch compression inside the RF gun injection system, we will investigate more on this. We have add new capabilities to Parmela code so we can study how slice emittance and select arbitrary part of beam to optimize the performance. We will investigate how solenoid magnet pole shape to improve the performance.