A Compact Photon Source for the WACS Experiment At JLab

Compton scattering off the nucleon is one of the simplest processes that can provide valuable information for the understanding of the nucleon structure. A Wide Angle Compton Scattering experiment requires a high intensity photon source based on the CEBAF electron beam, that can safely operate in Hall A at JLab. One of the hardware tasks for a team proposing an experiment is to consolidate the design of the photon source, simulate its performance, and then build it. The solution illustrated here is an untagged bremsstrahlung γ source consisting of a 10% radiation length radiator and a normal conducting magnet to sweep incident beam electrons out of the beam line, with proper shielding inside and around the magnet, making it a sort of mini beam dump. The magnet bore has a tungsten-copper block with a set of small openings (2 mm by 20 mm), designed to be 1 m long. It will slowly move along a vertical axis to perform as a "mechanical raster", to protect the polarized target from local overheating.