UPGRADE DESIGN OF KU-FEL DRIVER LINAC USING PHOTO-CATHODE RF-GUN

Upgrade design of KU-FEL driver linac has been carried out to obtain a stable oscillation in the infrared FEL. The existing 4.5-cell thermionic RF gun will be operated with a photocathode to enhance the FEL gain. The numerical evaluation of beam properties is carried out from gun to FEL by using PARMELA and TDA3D. The evaluated peak current is 4 times and the expected FEL gain is 10 times as high as those with the thermionic cathode. A 1.6-cell photocathode RF gun dedicated to photocathode operation is also examined to obtain an excellent electron beam. Expected FEL gain is more than 2 times as high as the gain with the 4.5-cell photocathode RF gun.