HPGe Spectrometer as a Gamma Ray Dosemeter <italic>In Situ</italic>

Abstract

A new gamma ray dosemeter utilising in situ gamma spectrometric measurements by a HPGe spectrometer is described. The spectrometric method for calculation of the real incident gamma ray spectrum is based on factorisation of the response operator. A set of common factors has been used that result from fundamental photon interactions with matter. The scaling and loading coefficients for the common factors have been estimated by a confirmatory least squares technique of factor analysis that makes it possible to create a response function in the response operator for an arbitrary energy of the measured range up to 1.8 MeV. Performance of radial and angular calibrations of the spectrometer yield certain conditions in regard to in situ applications. For the case of an unknown angular distribution of gamma sources, a correction according to the Dewar flask shielding must be carried out. The correction method, which is discussed in detail, allows one to estimate the angular distribution of sources by a set of measurements using a HPGe detector rotated around the effective centre of the detector to different directions. The real incident fluence rate spectra obtained may be employed in the determination of basic dosimetric characteristics such as spectral exposure and dose rates. Comparison of the calculated and the measured values is presented for a modelling distribution of point gamma sources