An algorithm for intrinsic gain and offset stabilization of gamma-ray pulse height spectra

The authors describe a novel algorithm for the intrinsic stabilization of the pulse height spectra (PHS) of multiply scattered gamma -rays which does not rely on the use of radioactive check sources, but makes gain and offset corrections based on spectral shape. In the implementation, the input spectrum is transformed (interpolated) from assumed (trial) values of gain and offset to a set of standard values, the PHS are projected onto four spectral principal components, and the mean square error between the transformed input spectrum and its rank four representation is minimized. For noise-spectra, it is found that the algorithm can estimate gain with a RMS (root-mean square) error of 1%, and offset with an RMS error of 0.6 keV when the spectral components are determined from the test data. For noisy spectra the RMS error for gain and offset are 4% and 1.7 keV, respectively.<>