Wide energy range efficiency calibration method for Ge detectors

A new method is proposed for the relative efficiency calibration of HPGe detectors in the energy range from 50 keV to 11 MeV. By simultaneously fitting all separately measured data sets from calibrated and uncalibrated multigamma sources as well as neutron capture γ-rays with a sum of orthogonal polynomials on a log–log scale, accuracies better than 0.5% between 100 and 3500 keV and better than 1% up to 6000 keV could be achieved for relative full energy peak efficiencies. Dividing the energy range and fitting piecewise with lower-order polynomials does not offer any advantage. Moreover, none of the popular non-linear empirical functions are able to fit the full range. The polynomial fit is nearly indistinguishable from a semiempirical fit. If at least one calibrated γ-ray source is included, the method can be used for absolute efficiencies as well.