Measurement of laser-induced Compton backscattered photons with anti-Compton spectrometer

Quasi-monochromatic photons of energies of 1.6-8.7 MeV have been generated by the Compton backscattering of laser light on relativistic electrons in the TERAS storage ring. The spectra of the backscattered photons have been measured with an anti-Compton spectrometer system. The present system has a 155-cm³ a coaxial-type pure-Ge detector as the central detector and a well-type NaI(Tl) scintillator of 8-in φ×8-in as the outer one. With a usual anticoincidence technique, clear photopeak spectra were obtained with a Compton suppression ratio of 2-4. The maximum energy and the energy spread of photons show reasonable agreement with numerical calculations. The divergence and energy spread of the electron beam in the storage ring are estimated from the data