Prompt Neutron Gamma Spectroscopy (PNG) measures ratios of gamma intensities after thermal neutron cature in Si to determine the fi. The only way of perform calibration and measurement is to compare the unknown sample with the reference sample mentioned, both samples being of equal size and shape. The problem is that the gamma peaks in a Ge detector usually sit on high (compton)-background. It was investigated in detail as to how far this can be improved by proceeding from single spectra to coincidence spectra and to borehole detectors. The result is that with the improved signal to background ratio, the lower counting statistics demand too long counting times for the precision needed.
