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Hubbard, Michael; Buggey, Thomas; Hall, David; Feldman, Charly; Keelan, Jonathan; Hetherington, Oliver; Parsons, Steven; Arnold, Timothy and Holland, Andrew
(2024).
DOI: https://doi.org/10.1117/1.JATIS.10.3.034003
Abstract
Space observatories utilizing micro pore optics (MPOs) have been used and are planned for several future X-ray astronomy space missions. The optical systems are designed to facilitate the focusing of incoming photons onto the focal plane of telescopes. Unfortunately, as well as having a small solid angle “open” to the sky, MPOs also have the unintentional effect of focusing high-energy particles from the space radiation environment. This causes additional radiation damage to mission-critical imaging sensors with solar energetic particles being particularly focusable. Typically, processes such as sectoral analysis are used to estimate the predicted dose to components, which is a ray tracing approach, and does not include focusing effects. We investigated focused dose estimation techniques for MPOs using Monte Carlo (MC) simulations. The focused dose contribution was compared with the unfocused contribution for the Solar wind Magnetosphere Ionosphere Link Explorer mission. The unfocused dose estimates were calculated using a traditional sectoral shielding analysis. The Monte Carlo-focused dose simulations enabled dose mapping over the image sensor to be analyzed. This revealed a relatively uniform dose across the device with some focusing artifacts present. The simulations also showed that the total ionizing dose and total non-ionizing dose decreased with depth into the sensor from the entrance window. This is key when considering that charge is often stored at varying depths in imaging devices across different technologies, for example, in front or back illuminated devices.