Radiation Safety Aspects of the Linac Coherent Light Source at SLAC Sayed/H Rokni*, SLAC National Accelerator Laboratory ; James/C Liu, SLAC National Accelerator Laboratory; X. Stan Mao, SLAC National Accelerator Laboratory; Alyssa/A Prinz, SLAC National Accelerator Laboratory; Mario Santana Leitner , SLAC National Accelerator Laboratory; Joachim Vollaire, SLAC National Accelerator Laboratory

Abstract: The LCLS (Linac Coherent Light Source), a 4th generation light source at the SLAC National Accelerator Laboratory, is the world first hard X-ray Free Electron Laser (FEL). Electron bunches generated in a new photoinjector are accelerated through the last third of the existing SLAC 2-mile-long linac to energies ranging from 3.3 GeV to 15.1 GeV. The electron bunches of 3400 A peak current and ultra-low emittance are transported through a 130-meter long undulator producing high brightness and ultra fast (~100 fs long) pulses of coherent x-ray between 0.5 keV and 10 keV, The electron beam is bent down into a shielded beam dump while the spontaneous and FEL photons are transported at forward angle to the Front End Enclosure (FEE), where the desired FEL beam quality and intensity is tuned and can be delivered to instruments in any of the six experimental stations located in two halls down beam of the FEE. While some of the radiation protection issues for the LCLS are similar to those encountered at both high-energy electron linacs and synchrotron radiation facilities, LCLS poses unique challenges as well. The unique issues for FEE and experimental stations include: user occupancy near zero degrees with respect to the electron beam direction, proper containment of errant electron beam into FEE and containment of bremsstrahlung radiation into experimental stations, and potential damage to the critical safety systems due to the high peak energy density of the FEL beam. The safety issues, as well as associated hazard analysis and mitigation and controls implemented, are presented. This work is supported by Department of Energy Contract DE-AC02-76SF00515.