Production of 10 MeV γ-ray by the backward Compton scattering using an optically-pumped FIR laser at SPring-8

For MeV γ-ray production by the backward Compton scattering (BCS), a high power optically-pumped far infrared (FIR) laser has been developed at the synchrotron radiation facility of SPring-8. We obtained about 1.6-W of output power of FIR laser at CH₃OH 119-μm lasing line pumped by 9P(36) branch line of CO₂ laser. We have constructed a test beamline for a production of 10-MeV γ-ray using an accelerator beam diagnosis beamline. FIR laser photons are injected to the beamline against 8-GeV stored electron beam and produced MeV γ-rays are extracted to the beamline. We proceed with a γ-ray production test at this beamline. It is estimated that the MeV γ-rays of 10³ photons/sec are obtained with FIR output power of 1.6 W at the test beamline. In future plan, the intensity of γ-ray can reach to 10⁷ photons/sec or more by means of installation of an intense MeV γ-ray production system by BCS at another new beamline.