High resolution prompt (n,γ) spectroscopy using a down hole logging tool

A down-hole logging tool is described utilising a 5 Ci²⁴¹Am–Be neutron source and intrinsic germanium gamma-ray detector. The tool was used to measure the prompt gamma-ray response from the irradiation of 4 well characterised coal samples. The correlation between the count-rate into the 2380 keV line arising from sulphur and the sulphur concentration as determined by chemical analysis is described. A depression in the count rate into the sulphur peak of interest is modelled using the neutron transport code ANISN and compares well with measurement. The influence of borehole diameter and the presence of borehole fluid upon logging performance is assessed.