Research on accurate virtual trajectory length model for TGS transmission measurement

摘要: In order to accurately reconstruct the TGS transmission measurement image, this paper optimized the trans#2;mission reconstruction equation according to the actual situation of TGS transmission measurement. Based on the transmission reconstruction equation and the Monte Carlo program Geant4, an innovative virtual trajectory length model was devised. This model integrated the solving process of trajectory length and detection efficiency within a same model. To mitigate the influence of the angular distribution of γ-rays emitted by the transmitted source at the detector, the transport processes of numerous particles traversing a virtual nuclear waste barrel with a density of 0 were simulated, and some information at each step of the particle transport were captured. Simultaneously, the model addressed the non-uniform detection efficiency of the detector end face by considering whether the energy deposition of particles in the detector equals their initial energy. Two models were established to validate the accuracy and reliability of the virtual trajectory length model: Model 1, a simplified nuclear waste barrel, and Model 2, which closely resembled the actual structure of a nuclear waste barrel. Research results indicated that the proposed virtual trajectory length model significantly enhanced the precision of trajectory length determination, substantially elevating the quality of reconstructed images. For example, comparing the reconstructed images of Model 2 using the "point-to-point" model and the average trajectory model, the SNR increased by 375.0% and 112.7%, respectively. Consequently, the virtual trajectory length model proposed in this paper holds paramount significance for the precise reconstruction of transmission images, and can provide support for accurate detection of radioactive activity in nuclear waste barrels.