LEPS Group


Overview of the beamline

The GeV photon beamline BL33LEP was constructed by a collaboration of RCNP, Japan Synchrotron Radiation Research Institute (JASRI), and Japan Atomic Energy Research Institute (JAERI).

BL33LEP overview

Backward Compton scattering (BCS) of ultraviolet laser photons off circulating 8-GeV electron beam in the synchrotron radiation (SR) ring produces a GeV energy polarized γ beam. UV or deep-UV laser photons are injected from the Laser Hutch into the straight section between the BM1 and BM2 bending magnets of the SR ring. By transferring momentum from an 8-GeV electron to a laser photon via the Compton scattering, the energy of the scattered photon becomes 2.4 or 3.0 GeV at the maximum, depending on the wavelength of the laser used. The scattered electron goes through the BM2 magnet and is detected with a tagging counter placed besides the CR2 chamber. By measuring the position of the electron at the tagging counter, using the BM2 magnet as a magnetic spectrometer, we can tag the energy of corresponding photon. Currently the lowest energy of the tagged photon is 1.5 GeV. The laser electron photon beam is transported to the Experimental Hutch and used for the experiments.