Radiation Effects on Ceramic Channel Electron Multipliers: Analysis, Simulation and Sensor Design
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The design of particle instruments to be operated in radiation hard environments is a challenge. Penetrating high energy radiation reaching the detectors causes signals that add to the signals generated by particles entering the instrument in a nominal way - up to the point where radiation effects completely dominate and nominal measurements become impossible. Long term exposure to radiation degrades detectors up to the point where they become unusable. Appropriate shielding can mitigate these problems, at the expense of extra mass needed. For new instruments the sensitivity of specific models of particle detectors to penetrating radiation and how they degrade over time is an important design parameter.In this study, a ceramic channel electron multiplier (CCEM) used in the PRIsma Mass Analyzer instrument (PRIMA), flown on the Swedish PRISMA (Prototype Research Instruments and Space Mission technology Advancement) mission, is characterized. PRISMA orbits Earth in an approximately circular polar orbit of 800km altitude. At this altitude, strong increased electron fluxes are observed when passing radiation belts or the South Atlantic Anomaly. Penetrating electrons create a clear signature in the recorded instrument data.The response of the CCEM to radiation and its time dependent degrading under these conditions is assessed by modeling the spacecraft radiation environment using the SPENVIS tool. Different methods are evaluated to model the shielding due to instrument and spacecraft structure, resulting in a predicted radiation environment at the location of the CCEM inside of PRIMA. Electron optical simulations are conducted using SIMION ion optical simulation software to calculate secondary electron collection efficiency from radiation exposed surfaces near the detector. Combined electron and x-ray fluxes to and through the CCEM detection volume are then compared to the measured count rate data to estimate the CCEM efficiency to detect electron and gamma particles for penetrating radiation. The time evolution of this quantity over the whole mission is then related to instrument operations resulting in design recommendations for future instruments. Within measurement and model uncertainties, the PRIMA CCEM performance showed to be comparable with predictions based on literature review. No statement can be made regarding time evolution of the performance because of the short instrument operation time. However, a future similar instrument on a similar mission should have increased shielding of the instrument to reduce sensitivity to penetrating radiation.
Place, publisher, year, edition, pages
2012. , 67 p.
Technology, CCEM detectors, Space Radiation
IdentifiersURN: urn:nbn:se:ltu:diva-50807Local ID: 80834048-1bea-4e65-9cc4-c4fbf20a4045OAI: oai:DiVA.org:ltu-50807DiVA: diva2:1024170
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
Validerat; 20120916 (anonymous)2016-10-042016-10-04Bibliographically approved