Upgrade of Beijing IR-FEL project

Beijing IR Free-Electron laser facility has been under upgrade in several aspects. For system modification, a new undulator beam line parallel to the old one that permits BFEL to simultaneously operate at two different wavelengths and a beam line to produce coherent synchrotron radiation and Compton back-scattering soft X-ray are being added. Optical beam pipe from undulator output to the experiment rooms is under fabrication. For improvement of the stability of operation, much work had 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 improving the laser performance, a new 312 cavity RF gun is pending installation, and a self-adaptive, feed-forward control system for beam loading compensation of the microwave electron gun to avoid longitudinal emittance blow-up has been successfully tested. Separate, independent RF power feeds of the RF gun and linac section will be implemented to facilitate the optimization of the operating conditions.