• A.P. Lee, C.H. Chen, C.S. Chou, J.-Y. Hwang, W.K. Lau, C.C. Liang
  NSRRC, Hsinchu
• J.H. Chen, N.Y. Huang, W.K. Luo
  NTHU, Hsinchu

A high brightness photo-injector for light source research applications is being built at NSRRC. This injector consists of a laser driven RF gun with an emittance compensation solenoid and linac sections that booster the beam energy up to 150 MeV. A 266 nm pico-second UV laser system which generates a 300 uJ laser pulse with pulse which can be varied by a UV stretcher from1 to15 ps have been installed and laser shaping techniques will be developed to reduce the emittance growth. The RF gun is a 1.6 cell cavity operating at pi mode and the solenoid used to compensate the emittance growth due to the space charge effect will be set up in the spring of 2009. Beam dynamics study is performed by PARMELA and simulation results show that a normalized rms transverse emittance of 0.7 mm-mrad with a 10 ps flattop pulse at 1 nC charge can be achieved. Measurements of characteristics of the RF gun and the solenoid will be presented.

• Y.-C. Huang, C.H. Chen
  NTHU, Hsinchu
• W.K. Lau
  NSRRC, Hsinchu

Funding: The authors gratefully acknowledge funding supports from National Synchrotron Radiation Research Center, National Tsinghua University, and National Science Council.

We study the generation of THz electron pulse trains from a 6 MeV photocathode electron gun driven by a beat-wave laser with a variable beat frequency [1]. We numerically inject the electrons into a single-pass FEL undulator. Owing to the prebunched electron pulse train, the quick shoot-up of the FEL power overcomes the space-charge debunching force in the 6 MeV beam. With nominal beam parameters and an initial bunching factor >5%, the FEL can reach 20-MW saturation power at 6 THz in a half meter long undulator. The length of this 20MW THz FEL, from the beginning of the electron gun to the end of the wiggler, is less than a meter. We will report our experimental progress of this work in the conference.

[1] Yen-Chieh Huang, “Laser-beat-wave bunched beam for compact superradiance sources,” International Journal of Modern Physics B, Vol. 21 Issue 3/4, p277-286 (2007).