HPGE SPECTROMETER AS A GAMMA-RAY DOSIMETER IN-SITU

A new gamma ray dosemeter utilising in situ gamma spectrometric measur ements by a HPGe spectrometer is described. The spectrometric method f or calculation of the real incident gamma ray spectrum is based on fac torisation 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 est imated by a confirmatory least squares technique of factor analysis th at makes it possible to create a response function in the response ope rator for an arbitrary energy of the measured range up to 1.8 MeV. Per formance 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 accordi ng to the Dewar flask shielding must be carried out. The correction me thod, which is discussed in detail, allows one to estimate the angular distribution of sources by a set of measurements using a HPGe detecto r rotated around the effective centre of the detector to different dir ections. The real incident fluence rate spectra obtained may be employ ed in the determination of basic dosimetric characteristics such as sp ectral exposure and dose rates. Comparison of the calculated and the m easured values is presented for a modelling distribution of point gamm a sources.