Publication
Initial simulation of a gaseous Compton camera with electroluminescence amplification
| Summary: | Although Anger cameras are commonly used in medical imaging, they still have an issue where, at higher photon energies, there is a drop in detection efficiency. A possible solution to counteract this problem is being pointed as Compton cameras. Separate simulations of a Compton camera and a Field-Assisted Transparent Gaseous Electroluminescence Multiplier (FAT-GEM) were performed with the objective of determining the optimal conditions for each component of the detector. In the Compton camera simulations, 10⁸ incident photons with energies of 60, 140, 364, and 511 keV were simulated for a Xenon gas filling at 10 bar. It was shown that the Doppler broadening effect decreased with an increase in incident photon energy. Beyond 364 keV, the photon’s energy did not seem to have major effects on the angular resolution due to Doppler broadening. It was demonstrated that increasing the incident energy decreased the number of Compton events detected. Simulations of electron transportation within Xenon gas inside a FAT-GEM structure were conducted for different drift and electroluminescence fields in 2, 3, and 4 mm holes at 2, 4, 6, 8, and 10 bar. It was verified that there was a variation in the number of excitations with the drift field, where the number of excitations decreased for higher fields. In general, increasing the drift field also increased the Qᵥₐlᵤₑ due to the loss of electrons to the electrodes. All hole geometries showed a linear increase in the number of excitations with the increase of the electroluminescence field, while the number of excitations decreased with the increase in hole diameter. In general, the Qᵥₐlᵤₑ started decreasing as the electroluminescence field increased until it reached the ionization threshold, where it began to increase due to the higher statistical fluctuations typical of the gas ionization process. Higher pressures showed a decrease in the Qᵥₐlᵤₑ due to the increase in the number of excitations. On the other hand, increasing the hole diameter increased the Qᵥₐlᵤₑ. Using a 2 mm hole in an 8 bar environment with a 3.6 kVcmˉ¹barˉ¹ electroluminescence field, the lowest Qᵥₐlᵤₑ was achieved. |
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| Main Authors: | Lucas, Francisco Miranda |
| Subject: | Compton camera FAT-GEM Gaseous radiation detector Electroluminescence amplification Medical imaging |
| Year: | 2023 |
| Country: | Portugal |
| Document type: | master thesis |
| Access type: | open access |
| Associated institution: | Universidade de Aveiro |
| Language: | English |
| Origin: | RIA - Repositório Institucional da Universidade de Aveiro |
| Summary: | Although Anger cameras are commonly used in medical imaging, they still have an issue where, at higher photon energies, there is a drop in detection efficiency. A possible solution to counteract this problem is being pointed as Compton cameras. Separate simulations of a Compton camera and a Field-Assisted Transparent Gaseous Electroluminescence Multiplier (FAT-GEM) were performed with the objective of determining the optimal conditions for each component of the detector. In the Compton camera simulations, 10⁸ incident photons with energies of 60, 140, 364, and 511 keV were simulated for a Xenon gas filling at 10 bar. It was shown that the Doppler broadening effect decreased with an increase in incident photon energy. Beyond 364 keV, the photon’s energy did not seem to have major effects on the angular resolution due to Doppler broadening. It was demonstrated that increasing the incident energy decreased the number of Compton events detected. Simulations of electron transportation within Xenon gas inside a FAT-GEM structure were conducted for different drift and electroluminescence fields in 2, 3, and 4 mm holes at 2, 4, 6, 8, and 10 bar. It was verified that there was a variation in the number of excitations with the drift field, where the number of excitations decreased for higher fields. In general, increasing the drift field also increased the Qᵥₐlᵤₑ due to the loss of electrons to the electrodes. All hole geometries showed a linear increase in the number of excitations with the increase of the electroluminescence field, while the number of excitations decreased with the increase in hole diameter. In general, the Qᵥₐlᵤₑ started decreasing as the electroluminescence field increased until it reached the ionization threshold, where it began to increase due to the higher statistical fluctuations typical of the gas ionization process. Higher pressures showed a decrease in the Qᵥₐlᵤₑ due to the increase in the number of excitations. On the other hand, increasing the hole diameter increased the Qᵥₐlᵤₑ. Using a 2 mm hole in an 8 bar environment with a 3.6 kVcmˉ¹barˉ¹ electroluminescence field, the lowest Qᵥₐlᵤₑ was achieved. |
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