FEL and CSR at UVSOR-II

operated for nation-wide users with small emittance of 27 nm-rad and four undulators [1]. By utilizing beam time for accelerator studies, which is about 20 % of the total operation time, coherent light source technologies are being developed. A resonator type free electron laser (FEL) has been studied for many years. Thanks to the recent upgrades on the accelerator [2, 3, 4], lasing in deep UV region up to 199 nm has come to be possible [5]. Lasing at even shorter wavelength seems promising. Several user experiments have been started on this tunable and high power laser [6, 7]. Coherent harmonic generation (CHG) was tried by using a Ti:Sa laser. Coherent 3rd harmonics was successfully observed [8]. Observation of higher harmonics in VUV is under planning. Broadband coherent synchrotron radiation (CSR) in terahertz (THz) region was successfully produced by using laser slicing technique [9]. Recently, narrow band and tunable THz CSR was successfully produced by using amplitude-modulated laser pulses [10]. Intense bursts of THz CSR were observed in single bunch operation with high beam current [11], which was most likely due to some instability. Bursts of THz CSR were also observed during Q-switching operation of the FEL, which was interpreted as the results of continuous interaction between the electron beam and th