Estimation of photon energy spectra based on 34 x 34 response matrix

The 34 x 34 response matrix whose energy divisions were chosen as 0.02 MeV between 0 and 0.1 MeV and chosen as 0.1 MeV between 0.1 and 3 MeV was constructed, and pulse-height distributions obtained by 3''phi spherical NaI(tl) scintillation spectrometer were unfolded by a response matrix method into true photon energy spectra. The derived spectra were discussed precisely in the energy region from 0 to 3 MeV. Exposure rates were calculated from the spectra, and these values were compared with those measured with an ionization chamber to make sure the total number of incident photons on the detector. (auth.)