YAlO3: Ce-Am light pulsers as a gain monitor for undoped CsI detectors in a magnetic field

YAlO3-Am pulsers show no degradation in their light output or resolution upon the application of a magnetic field, at least up to 10 kG. The decrease in the pulse height agrees with the change in the PMT gain calibrated by an LED. When the pulser is mounted on the top face of a 30 cm long CsI far from a PMT with a UV filter inserted between the PMT and the CsI, the light output decreases by a factor of 14, compared with the case of being directly mounted on the PMT window. In the above configuration, the 5.49 MeV α of 241Am gives about 550 photoelectrons, which corresponds to a γ-equivalent energy of 6.6 MeV. Finally, the pulsers were mass-produced with a FWHM resolution of 5.4% (average) for the pulse height.