Broad Energy HPGe Gamma Spectrometry for Dose Rate Estimation for Trapped Charge Dating

Gamma-ray spectrometry has been widely used in various environmental and natural sciences by its ability to determine the concentrations of each radionuclide of the samples, and also because of the easiness in sample preparation and measurement procedures. Recently, its applicability is being extended for Quaternary geochronology, by providing information on the rate of energy absorbed by phosphor minerals (i.e. dose rate) used in trapped charge dating methods. To measure the radionuclides emitting low energy gamma ray (particularly, Pb and Th), which are subjected to be easily absorbed by detector-cryostat materials and sample itself, various HPGe detectors have been developed, because these detectors have high resolution capacity and are relatively easy for maintenance. In this paper, we review the characteristics of p-type coaxial HPGe, well-type HPGe and broad energy HPGe (BEGe) gamma-ray detector, and these are compared with each other, particularly with a view to establishing the most appropriate measurement procedure for estimating the dose rate for trapped charge dating methods. Also various calibration factors to analyse the low-level environmental samples are discussed. Especially self-absorption correction method using sample weight is suggested.