Determination of the number of pulsed laser-Compton scattering photons

We measured pulse-height spectra of 16.7 MeV laser-Compton scattering photons with a 6 in.×5 in. NaI(Tl) detector for blank and three lead materials of 75.8, 50.9, and 25.9% transmissions at the NewSUBARU facility to investigate how the original Poisson distribution of the pulsed photons is modified after passing through thick-target materials. We present a well-prescribed method of determining the number of incident photons within 3.5% accuracy based on the response of the NaI(Tl) detector to the pulsed photon beams.