  Low background gamma spectrometry employing HPGe detectors is a sensitive
technique for measuring low-level radioactivity in environmental applications,
material screening, and for rare decay searches. This work presents
spectroscopic performance evaluation and modelling of a low background
measurement setup developed at IIT Ropar in Punjab, India, to measure trace
natural radioactive elements, with a particular interest in studying low-level
radioactivity in soil and/or rock samples to generate specific inputs for low
background experiments. The performance test and characterization of a low
background cryocooled HPGe detector with relative efficiency of $\sim$33% have
been carried out. An effective detector model has been developed using GEANT4
Monte Carlo simulation to determine the response of the detector over an energy
range of 80.9-1408 keV and compared with the experimental performance of the
detector. The response of the detector obtained using Monte Carlo simulations
agrees reasonably well within 93% level of confidence, indicating only 7%
deviation in the comparison. The present setup offers improved detection limits
of primordial radionuclides (U/Th and K) to measure radioactive contamination
in environmental matrices, which has been used elsewhere [1].
