• 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.

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

The feasibility of generating sub-hundred femtosecond X-ray pulses based on inverse Compton scattering of relativistic electron pulses of 50-100 fsec with an 800 nm, 37.5 GW infrared Ti:Sapphire laser has been studied. The feasibility of generating sub-hundred femtosecond X-ray pulses based on head-on inverse Compton scattering (ICS) of relativistic electron pulses with laser has been studied. Relativistic electron pulses of 13.55 fsec can be produced by compressing the energy-chirped beam from a thermionic cathode rf gun with an alpha magnet *. This beam has an intensity of ~ 3.31x10⁸ e^- per bunch and is accelerated to 20.5 MeV with an S-band linac structure and is focused to 30 μm for scattering with an 800 nm, 3.75 mJ infrared Ti:Sapphire laser in the laser-beam interaction chamber. With this method, peak flux of back-scattered X-ray photons as high as 2.17x10¹⁸ photons/sec is achievable at ~ 1.24 Å wavelength. This femtosecond X-ray source is planned to be used as a tool for studying ultrafast phenomena in nanostructure in the near future.

*P. Kung, H.C. Lihn and H. Wiedemann, “Generation and Measurement of 50-fs (rms) Electron Pulses”, Phys. Rev. Lett. Vol.73, p.967-970, August 1994.

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

A 266nm ultra-violet laser system has been installed as the drive laser of the NSRRC photoinjector. According to beam dynamic studies for the photoinjector, a 10ps uniform cylindrical beam will be generated at the Cu cathode to reduce emittance growth due to space charge and transverse RF fields in the photoinjector cavity. The main part of this system is diode laser pumped, 798nm regenerative IR amplifier that can provide 85fs pulse at 3.85mJ pulse energy. The conversion of frequency from IR to 266nm UV is achieved by a third harmonic generator. UV output pulse energy exceeds 300uJ. Synchronization between seed laser and the high power microwave system can be better than 1ps. In order to produce a uniform cylindrical beam for emittance reduction in the photoinjector, a refreactive UV beam shape and a pulse stacking temporal beam shape are being implemented.