Segmented HPGe (High Purity Germanium) detectors are commonplace in nuclear structure studies, where position and amount of energy deposited by the photon’s interactions inside the detector are fully reconstructed at every event using the pulse shape analysis methods. Recently a similar segmented HPGe detector concept in combination with a multi-slit collimator was proposed for gamma emission tomography. The feasibility of the proposed concept for use in gamma emission tomography and its performance was evaluated by a simulation study. A segmented HPGe can offer high energy resolution and high spatial resolution, and its ability to simultaneously interrogate the fuel object with multiple detection elements can also make it suitable for faster operation requirements in the post-irradiation examinations (PIE). The use of such segmented HPGe detectors can facilitate imaging of nuclear fuel rod internal features like fission product migration, pellet cladding interactions, rod bow and swelling, fuel fragmentation, relocation and dispersal in transient tests etc., as well as for analysis of miniaturized irradiation tested fuel samples.
It is important to quantify the spatial resolution achievable by using the collimated segmented HPGe before the actual detector is manufactured and operated. The spatial response for a segmented HPGe detector concept was evaluated using simulation with Monte Carlo N-particle transport code MCNP6. Full detector and multi-slit collimator system was modelled and for the quantification of the spatial response, the Modulation Transfer Function (MTF)/Contrast Transfer Function (CTF) was chosen as the performance metric. These performance metrics were obtained through the calculation of the Line Spread Function (LSF) and Edge Spread Function (ESF) by analysing the simulation data. In addition, the proportionality between the activity inside the object and the as-measured profile with the detector collimator system was also examined through simulations of a ramp pattern/stair-step pattern.
The results from the simulation study will be presented at the ANIMMA-2021 conference.