Abstract
Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples.In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined.
Highlights
Gamma Emission Tomography (GET) is a non-intrusive technique to image the interiors of gamma-emitting objects
As detailed in Ref. [8], a segmented HPGe detector (Fig. 1) for GET measurements was proposed consisting of a single monolithic germanium crystal where a number of electrodes electronically define the segmentation of the detector
The results of Ref. [8] suggested that a segmented HPGe detector could be feasible with a detection efficiency in the range of 19%–28% and with a negligible misidentification rate
Summary
Gamma Emission Tomography (GET) is a non-intrusive technique to image the interiors of gamma-emitting objects. During GET measurements, gamma-ray intensities from such objects are measured at various positions and from these, the internal activity distribution may be reconstructed using dedicated software [1,2,3,4]. If these measurements are carried out spectroscopically, the spatial distribution of various radioactive nuclides can be deduced. [8], a segmented HPGe detector (Fig. 1) for GET measurements was proposed consisting of a single monolithic germanium crystal where a number of electrodes electronically define the segmentation of the detector Each of these segments is coupled to a collimator slit to obtain the desired spatial resolution. Acquisition and system integration will be subjects in forthcoming work
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