Radiation Field Unfolding at the Free Electron Laser in Hamburg (FLASH) using a Genetic Algorithm

In Summer 2005, a high brilliance, vacuum ultraviolet (lambda=13 nm) free electron laser named FLASH (free electron laser in Hamburg) commenced its routine operation at DESY in Hamburg. The FLASH is driven by a 700 MeV electron linac based on high-purity superconducting Niobium cavities developed by the TESLA Technology collaboration at DESY. The gamma radiation doses along the containment tank walls of the accelerator modules 4 and 5 of the electron linac were evaluated using radiochromic films during its routine operation. This paper highlights a genetic algorithm (GA) developed by us in order to unfold the dosimeter readings. The unfolded data were used to inverse calculate the radiation source strength at the cavities, thereby quantifying the field emission induced radiation produced by each individual cavity belonging to the accelerator module.