Charged Particle Environment Testing of a Deep Space Radiation Shield with Associated Fabrication and Calibration of Pulsed Power Systems
Moffett, Mark Bedford
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Space radiation is one of the primary dangers faced outside of the protective magnetosphere of Earth. Despite the persistent radiation threat to self-contained human habitation and the risk of increased exposure during long-duration missions, reliable long-term radiation protection is not well-developed. Active shielding is an avenue of preventative radiation protection that could be deployed to protect astronauts and biological life from the effects of radiation. This dissertation explores the design scalability of an active magnetic shield for protecting against isotropic radiation in deep space. Each shield is composed of two concentric, elliptical layers of circular conducting coils, each arranged like lines of latitude on a globe, with the current modulated to amplify the magnetic field in the layer between the ellipses, and canceling within. The parametric scalings are verified through ANSYS magnetostatic modeling and corresponding 3D-printed test article demonstrations matching vector magnetic field models. This dissertation demonstrates the first experimental test of a functional field reversed configuration geometry that can deflect charged particles while also producing a magnetic null in the habitable zone. Numerical analyses, including the integral field parameter, are used to experimentally determine the magnetic field to deflect electrons. Successful pulsing between 250-1900A demonstrated shielding of approximately 11-keV electrons at ever higher levels. Bdot probes and Rogowski coils are used in the measurement of transient magnetic fields and currents, respectively. They both share the mechanism of creating an induced electromotive force response via Faraday’s law. High power capacitor direct current (DC) discharge systems release a single pulse of current that is both very high (kA) and very fast (1 ms). Using robust analytical calculations, finite element analyses, and empirical methods, we have developed a sensor fusion protocol for current and magnetic field probes (relative errors of ±13% and ±15%, respectively) for use in any geometry of high speed pulsed DC current calibrated capacitor discharge systems. This dissertation comprehensively outlines the design and sensor fusion methodologies that allow for the deployment of in-house built Bdot probes and Rogowski coils to a wide range of pulsed DC systems and demonstrates their use in a characteristic plasma environment.