Generation of laser Compton gamma-rays in the SAGA light source storage ring

A medium-scale synchrotron light source of GeV-class equipped with an infrared high-power laser can generate stable high-flux gamma-rays at several MeV via laser Compton scattering. We constructed an experimental setup for high-flux gamma-ray generation in the SAGA light source storage ring. A head-on collision between a 1.4 GeV electron beam and laser photons with a 10.6μm wavelength produced gamma-rays up to a maximum energy of 3.5 MeV. Since the laser Compton scattering does not influence the beam quality, these gamma-rays can be generated in conjunction with user time for synchrotron radiation research. The event rate was designed to be 1.4×108s-1 with a beam current of 300 mA and a laser power of 10 W. As a first step in high-flux gamma-ray generation, we performed beam tests at a low beam current to evaluate the characteristics of the gamma-rays. Gamma-ray generation with no reduction in beam lifetime was confirmed by these tests. The experimental results show that the effective gamma-ray flux was almost 40% of the design value. The laser Compton gamma-ray was also applied to measure the machine parameters of the storage ring. The beam energy was successfully determined with relative uncertainties on the order of 10-3 by analyzing the gamma-ray spectrum for the stored beam, which ranged in energy from 0.6 to 1.4 GeV.