THE STUDY OF DRIVE LASER SYSTEM FOR PHOTO-INJECTOR *

A drive laser system is developed in Peking University. It is a pioneer technical study for Shanghai Light Source, whose purpose is to study DUV-FEL. The beam energy is designed to 300 MeV and the coherent radiation wavelengths from 300nm to 75 nm. The photocathode electron gun will use copper as the cathode material. It requires the drive laser to provide 500µJ, 6~ 8ps pulse of UV photons (260nm) to the cathode. To satisfy spatial and temporal requirements of the laser pulse, we adopt Ti:sapphire lasers to make up of the main frame of this system. It mainly consists of such lasers: a CW, frequency-doubled, diode-pumped Nd: YAG laser which provides energy to pump a CW mode-locked Ti: sapphire oscillator, a frequency-doubled, Q-switched Nd:YAG laser to pump a multi-pass amplifier, a regenerative amplifier and harmonics crystals. The cavity length of the oscillator should be adjustable in order to lock the pulse frequency with external RF reference, and a phase stability feedback system is also used. Now, the conceptual design of this system is finished