Control of a Storage Ring Free-electron Laser by Modulating an Electron Bunch

We have studied a storage ring free-electron laser (FEL) with a compact storage ring NIJI-IV, which was constructed at National Institute of Advanced Industrial Science and Technology in 1990. We have developed an infrared FEL system with using one of the long straight sections in the NIJI-IV [1], and the FEL is realized with a fundamental harmonic of an insertion device, optical klystron ETLOK-III, in a wavelength region of 8392679 nm [2]. Higher-harmonic FEL oscillations have been also developed with the infrared FEL system [3]. FEL oscillations were achieved up to the seventh harmonic, which is the highest order in higher-harmonic FEL oscillations [4].