Publications
The incorporation of silicon photomultipliers into Cherenkov detector systems offers a new standard for satellite programs, utilising the small volume and power draw of the devices to design setups that can be used in CubeSat missions. One such implementation proposed is that of a high-energy proton detector to monitor the flux of particles in low Earth and geostationary orbits. Of particular interest are protons produced in solar events with energy greater than 300 MeV that pose a threat to space missions, aircraft and ground-based infrastructure. A detector can utilise the inherent energy threshold of the Cherenkov light production mechanism to monitor the high-energy proton enhancement due to these solar energetic events, above the typical trapped proton and GCR levels in orbit. We present the development of a SiPM-based Cherenkov detector system and display its capability to discriminate between protons with energies around a given radiator’s Cherenkov energy threshold.
Cherenkov detectors have been used in space for decades to measure Galactic Cosmic Rays (GCRs), Solar Energetic Particles (SEPs) and trapped particles. We present proof‐of‐concept GRAS/Geant4 simulations to both show that a cubic fused silica Cherenkov detector with SiPM in LEO has a good sensitivity to SEP and GCR protons as a function of cut‐off rigidity and trapped protons in the South Atlantic Anomaly (SAA), and to characterize/mitigate the background that this detector would experience. We find that Cherenkov count rates due to most particle components vary significantly depending on many different factors, including the location in the orbit and solar particle event characteristics. We also investigate the use of coincidence as a method to remove background due to trapped electrons and delta electrons, finding this method is very effective for resolving count rates due to GLEs amongst intense trapped particle environments, but some Cherenkov count rates due to trapped particles are still observed in the simulated SAA region. Plain Language Summary Radiation in space near Earth is very complex, and varies with time as well as with location in Earth's magnetic field. Despite decades of research, there are still many unknowns about the composition, energy spectrum and time dependence of radiation near Earth, particularly during large solar events. In this research we investigate the feasibility of using small Cherenkov detectors for measuring the radiation environment around Earth. Recent advances in silicon photomultiplier technology have meant that small Cherenkov detectors can be made relatively cheaply, and be placed in orbit on small satellites. The simulation results presented in this paper show that small Cherenkov detectors should be capable of measure many interesting types of radiation in a low‐Earth orbit, with the energy spectra of particles trapped in Earth's radiation belts and particles during solar events being of particular interest. We anticipate that detectors of the design simulated here could be used in combination with ground based neutron monitors to increase our understanding of atmospheric radiation levels that aircraft experience during high‐energy solar events.
Ground level enhancements (GLEs), which occur when high energy solar protons reach Earth, are a considerable space weather hazard for aviation activities. Neutron monitor (NM) observations of these events are the key input to operational models of ionizing radiation at aviation altitudes. Similarly, the NM data is key to techniques for deriving anisotropic solar proton spectra during GLEs. A higher density of observations is desirable for both purposes. In this paper, a simple way of improving the density of observations for large events is presented: the compact neutron monitor (CNM). This monitor uses the same unleaded detectors as soil moisture sensing networks. Three years of data from the CNM located in Guildford, UK, is presented. The solar cycle variation in cosmic rays is observed, alongside 4 Forbush decreases of varying magnitude. No GLEs were observed during this time, due to a lack of any events of sufficient magnitude to be observed. A future CNM station near Lerwick, UK is briefly described in addition to the Guildford station. The implications of the observations to date are discussed in the context of GLE detection. The CNM is complementary to existing and emerging NM designs, and may be suitable for use as a reference point for the soil moisture monitoring networks. The suitability of the CNM to GLE detection can be extrapolated to the soil moisture networks in the case of large GLEs; in the event of one occurring, the data may provide unprecedented spatial resolution.