Abstract :
This paper points out the importance of studying case histories in courses of instruction on nuclear instrumentation, and that the byproducts of such studies can often provide useful research projects. The case of the gamma backscatter density gauge is considered as a specific example. Starting from the original type of gauge, using a fixed source-detector separation in which a counting rate vs density chart is employed, the authors discuss the elimination of "soil type" effects, the anomalous behaviour of hydrogen, etc. to the new moving-source (variable source-detector distance) gauge, and the advantages which it offers, e.g. no calibration being necessary, etc. Finally, more recent work is described showing how the density gauge may be employed for measuring the moisture content of materials as well as the density.
