Development of a Plasma Sensor to Study Multispecies Interactions in Hypervelocity Impact Plasmas

Hypervelocity impacts (HVIs) generate plasmas that are complex and time varying through multiple regimes of expansion. Understanding the bulk properties thereof will prove critical to the development of theories linking HVIs to the generation of RF radiation, hypothesized to be responsible for spacecraft damage. Existing models of these expansions ignore the complex interactions between various ion species, meaning that multi-ion instabilities are not well understood. Such instabilities would lead to the divergence of properties between different plasma species which would present themselves in the energy distribution functions (EDFs) thereof.

Here, a novel plasma sensor is proposed to study the EDFs by species in an expanding HVI plasma. The sensor design is based on a transient plasma array (TPA), designed to capture the EDF of all species using a series of electrostatic wells with walls charged to varying voltages to bin particles of specific energy ranges. The application of a time varying potential and the introduction of a magnetic field are considered to select for particles by energy and mass to probe the plasma temperatures of individual species; ion-ion streaming instabilities, the Weibel instability, and more will leave observable signatures. The ideal responses of the wells are explored computationally, and suites of wells then designed. Sensitivity to nonidealities is then explored, and a prototype sensor fabricated. Testing with thermionically emitted electrons is conducted to calibrate.