UPGRADE OF BEIJING IR-FEL PROJECT

Beijing IR Free-Electron laser facility has been under upgrade in seve ral aspects. For system modification, a new undulator beam line parall el to the old one that permits BFEL to simultaneously operate at two d ifferent wavelengths and a beam line to produce coherent synchrotron r adiation and Compton back-scattering soft X-ray are being added. Optic al beam pipe from undulator output to the experiment rooms is under fa brication. For improvement of the stability of operation, much work ha d been done to reduce the fluctuations of the electron beam parameters and the time jitter of the RF pulses. For extension of wavelength of operation, Au plated copper mirrors with axial out-coupling hole were used instead of the original multi-layer dielectric mirrors. For impro ving the laser performance, a new 31/2 cavity RF gun is pending instal lation, and a self-adaptive, feed-forward control system for beam load ing compensation of the microwave electron gun to avoid longitudinal e mittance blow-up has been successfully tested. Separate, independent R F power feeds of the RF gun and linac section will be implemented to f acilitate the optimization of the operating conditions. (C) 1998 Elsev ier Science B.V. All rights reserved.