Design, optimization and performance of source and detector collimators for gamma-ray scanning of a lab-scale distillation column

Abstract

When using source and detector collimators for gamma ray column scanning, it is important to obtain an acceptable density profile quality. This paper consists of two main works. The first is devoted to describing the designs used to optimize the source and detector collimators for a lab-scale distillation column, and the second is devoted to investigating the effect of designed collimators on the quality of the density profiles obtained using the gamma scanning technique. Simulations using the MCNP4C Monte Carlo code were performed to model the collimators and obtain the density profiles. The source and detector collimator designs were developed for a cylindrical volume source with the energy of 0.662MeV and 1in.×1in. NaI, respectively. The pinhole and panoramic collimator designs and the pinhole and quartic collimator designs were considered for the source and the detector, respectively. The source container, with an opening angle of 60°, has the capability of substituting the collimator for high resolution, general and high sensitivity purposes. The pinhole collimator parameters for the source that were obtained were generally quite coarse and were 1.2cm in diameter and 4cm in length. Additionally, the detector pinhole collimator thickness and length obtained were 4cm and 5cm, respectively. Using the semi-quartic collimator for the detector, the weight of required lead was reduced by over 33% compared with the pinhole collimator.The simulation results of the column scanning in abnormal operation condition have been validated by experimental measurement results. The obtained results from scans demonstrated that the optimized panoramic source collimator and semi-quartic detector collimator in this study could help us to obtain an acceptable density profile quality in total count approach.