Laser‐Compton Gamma‐Ray Source at a Beamline (BL1) in NewSUBARU

We have developed a laser‐Compton gamma‐ray source at beamline (BL1) in NewSUBARU, an electron storage ring operating at electron energies of 0.7–1.5 GeV. Initially, we generated 17–37 MeV gamma rays using a $Nd:YVO4$ laser operating at 1.06 μm and 0.53 μm, achieving a luminosity of 6000 photons/(W⋅mA⋅s) and a flux of $5×106 photons/s$ with a laser power of 4 W and a beam current of 200 mA. We then installed a $CO2$ laser operating at 10.6 μm, and generated gamma rays in the energy range of 1–4 MeV. In this range, the gamma‐ray luminosity is 7300 photons/(W⋅mA⋅s) and the flux is $5.6×106 photons/s$ when operating the laser at 4 W and 200 mA. These performances are in good agreement with calculations. We will next add a Tm‐fiber laser operating at 2 μm to generate gamma rays in the energy range of 4–21 MeV, using a laser‐focusing design to generate the maximum flux. The luminosity of this stage is calculated to be 6400 photons/(W⋅mA⋅s). $Nd:YVO4,$ $CO2,$ and Tm‐fiber laser are all capable of operating in a high‐power regime and can generate kW‐level output power. At present, the maximum gamma‐ray flux is limited only by the laser power. When operating the laser at 1 kW of output power with a beam current of 200 mA, we expect a flux of up to $∼109 photons/s.$ At NewSUBARU, up to several dozen MeV gamma‐ray sources are capable of generating such high power.