Abstract
The development of the Ce(Li) gamma ray spectrometer is incomplete in several areas, particularly those relating to, low level counting capabilities. A Ge (Li) gamma ray spectrometer was developed and several aspects of its performance were investigated. In particular, emphasis was placed upon cryostat operation and the Calibration, measurement, diagnosis and repair of detectors. Due to its significance in low level counting., the officiency of detection of rays has also been evaluated. It was found that some detectors had efficiencies of detection smaller than that expected from their size. Other problems associated in the optimisation of officiency were also considered. An expression has been derived, and experimentally Verified, for the sensitivity limit of a Ge(Li) spectrometer and is found to depend upon the absolute efficiency of detection, background continuum, energy resolution count time and the required statistical precisions This expression has been used to evaluate the significance of those parameters. The measurement of short lived isotopes has also been accounted for. Several counting configurations (e.g. coincidence, anti-coincidence and massive shielding arrangements) are available and have varying degrees of effectiveness when used for low level counting. A comparative method has been evaluate to evaluate the usefulness of each technique. It is found that massive shielding, certain. Alpha-gamma and beta-gamma coincidence, and anti-coincidence methods have the best low level measurement capability and can reach levels of the order of 1 pCi. Data is presented in certain cases to substantiate predictions. Such analyses are, valuable in that they can allow performance predictions for spectrometers. Evaluation of additions of new counting configurations (or detectors) to an exiting spectrometer is also, feasible. No previous analysis of this type has been undertaken.