Iterative Response Correction for a Scintillation Spectrometer

The application of scintillation crystals in the measurement of radiation spectra has increased rapidly in recent years and has been followed by a growing need for an efficient method of correcting for the response of the crystal and its associated phototube. Used in conjunction with an energy discrimination device such as a pulse height analyzer, the scintillation crystal conveniently gives the radiation intensity as a function of photon energy; however, distortion of the pulse height distribution occurs in both the scintillation crystal and the associated photomultiplier, and this must be corrected for whenever quantitative spectral distributions are required. The distortions are the result of two distinct effects: (1) the incomplete absorption of some of the X-rays incident on the crystal; (2) the normal statistical fluctuations which arise primarily in the photomultiplier. Since the measured pulse height distributions are obtained in numerical form on the conventional multichannel pulse height analyzer, the response of the detector may, for a given energy range, be represented by an m X m matrix, P, such that