Density-dependent HPGe efficiency from multi-gamma line ratios: a nominal-plus-self-shielding method and its MATLAB implementation

Gamma-ray self-attenuation in dense samples biases activities measured with a germanium detector. This method infers an effective sample density from the spectrum itself, using the relative intensities of several lines from each multi-gamma nuclide and a Monte Carlo efficiency that is a function of energy (keV) and sample density (g cm -3 ). Only the density dependence of the surface is applied to the laboratory calibration, so systematic errors in the detector model are largely removed. A MATLAB code automates peak search, identification, density fitting, uncertainty propagation and activity correction. In synthetic tests from 1.5 to 20 g cm -3 the fitted density was within 0.3 g cm -3 of the anticipated value.