High-energy gamma-ray beams from Compton-backscattered laser light

Collisions of light photons with relativistic electrons were previously used to produce polarized (BETA)-ray beams with modest resolution but relatively low intensity. The LEGS project (Laser + Electron Gamma Source) will produce a very high flux of background free polarized (BETA) rays whose energy will be determined to a high accuracy ((RADICAL)E = 2.3 MeV). The 300(420)-MeV (BETA) rays will be produced by backscattering UV light from the new 2.5(3.0)-GeV X-ray storage ring of the national synchrotron light source (NSLS). The LEGS facility will operate as one of many passive users of the NSLS. In a later stage of the project, a free electron laser is expected to extend the (BETA)-ray energy up to 700 MeV.