Design of High Energy Particle Detectors for Lunar and Low Earth Orbit Missions
Creators: Ball, Katelyn S
Publisher: name: University of Alberta Library
Year: 2023

<p>The study of energetic particles of solar and cosmic origin, and those accelerated in the planetary magnetopause, is integral to our developing understanding of the physical processes affecting space radiation in near-Earth space, interplanetary space, and Earth&#39;s upper atmosphere. In particular, accurate forecasting of space radiation is crucial when developing radiation risk assessment and mitigation strategies for human and robotic space exploration. This thesis presents an assessment and optimization of the layout and detection performance for three energetic particle telescopes designed for operation on the lunar surface, on-board the Lunar Gateway, and low Earth orbit (LEO). Geant4 monte carlo simulations are carried out to optimize each instrument’s response to the expected particle populations at their respective vantage points in space. The instruments use a stack of silicon detectors to measure the particle’s energy deposition, which is processed through algorithms  designed to identify the particle’s species and energy. \par<br>
The Lunar Lander SWeeping Energetic Particle Telescope (LL-SWEPT) is designed for a 14-day mission on the lunar surface. LL-SWEPT is primarily focused on assessing the relatively constant radiation risk due to Galactic Cosmic Rays (GCRs), as well as the secondary albedo particles from the lunar regolith. To measure statistically significant counts of GCR flux, LL-SWEPT has a geometric factor of 1.3 cm$^2$sr. Two energy identification regimes are used to measure lower (\textless 165 MeV) and higher energy protons from LL-SWEPT’s count rate data, enabling LL-SWEPT to make differential proton measurements with energies from 20 to 370 MeV, which extends past its required measurement range of 30 to 300 MeV. LL-SWEPT is also able to measure alpha particles with energies from 80 to 660 MeV. \par<br>
The Planetary Sweeping Energetic Particle Telescope (P-SWEPT) is optimized to operate on the Lunar Gateway. It has been shown that electrons accelerated from the Sun during solar energetic particle (SEP) events can reach Earth up to an hour before the proton flux, which provides the potential for an advance warning of strong SEP events. P-SWEPT prioritizes the measurement of proton and electron populations in SEP events, and its geometric factor of 0.113 cm$^2$sr is suitable for higher flux measurements. The energy identification regimes allow P-SWEPT to measure electrons with energies from 0.3 to 1.5 MeV and protons with energies from 22 to 400 MeV, which covers and extends past P-SWEPT&#39;s proton energy measurement requirement of 20 to 300 MeV. \par<br>
The RADicals High Energy Particle Telescope (RADHEPT) is a particle telescope suite set to fly on the upcoming RADiation Impacts on Climate and Atmospheric Loss Satellite (RADICALS) mission. The instrument suite on the RADICALS mission will study the processes which control space radiation precipitation into the atmosphere. The RADHEPT instrument is designed to measure electrons with energies from 0.08 to 4.4 MeV and protons with energies from 1 to 70 MeV, exceeding RADHEPT&#39;s measurement requirement for protons, 1 to 20 MeV, and electrons, 0.1 to 3 MeV. To make pitch angle resolved particle measurements, RADHEPT is required to measure particle count rates over six orders of magnitude. To do so, RADHEPT is comprised of two telescopes with geometric factors suitable to measure both the higher energy, low flux particles and the lower energy, high flux particles. The preliminary layout and detector performance of the high and low energy heads of RADHEPT are presented here as well as a scheme to use an anti-coincidence scintillator to detect off axis particles. \par <br>
The three instruments presented here will enable higher fidelity measurements of the radiation environment on the lunar surface, and in lunar and low Earth orbit, all of which are of significant importance both for the safety of future space exploration missions and impacts on the Earth&#39;s upper atmosphere.</p>