Conceptual Design Report A Compact Photon Source

Abstract

We propose to build a shielded magnet that will act as an untagged bremsstrahlung photon source suitable for deployment in Hall A/C at Jefferson Lab. The goal of the project is a compact source which provides a narrow 1-mm diameter photon beam at the target with the intensity adequate to the polarized target operation. The proposed solution is based on the absorption of the electron beam in the magnet. The compactness is achieved by means of a shallow channel which leads to an electromagnetic shower in the Cu-W body of the channel and surrounding material after a 1-2~mm deflection of the beam electrons by a horizontal magnetic field. This source will allow us to achieve ten times the luminosity of the mixed electron--photon beam configuration while keeping the heat load on the (polarized) target as well as the radiation level in the experimental hall at acceptable levels. The concept for this device was developed for the experimental proposal PR12-15-003 but, if built, it would become a general--purpose source that would be usable for a variety of photon--induced reactions of interest in the 12-GeV era.