Plasma Diagnostics I

This work presents the design and preliminary analysis of an Incoherent Thomson Scattering (ITS) diagnostic system developed to investigate electron properties within a magnetoplasmadynamic thruster (MPDT). MPDTs are considered a promising alternative to standard electrostatic technologies (such as Hall thrusters) for space propulsion. The properties measured with this technique are: electron density (via the spectral area, which reflects the number of scattering electrons), electron temperature (or electron energy velocity distribution function, inferred from the Doppler-broadened spectrum of the scattered light), and electron drift velocity (inferred from the degree of the shift of the spectrum away from the probing laser wavelength).

The experimental setup includes a high-power laser system, beam-shaping optics, and a collection path comprising a lens assembly, optical fiber bundle, volume Bragg grating notch filters, and an imaging spectrometer coupled to an iCCD camera. The collection optics are configured to capture scattered photons over a defined solid angle, determined by a lens mounted on top of a vacuum chamber and aligned with the plasma region between the MPDT cathode and anode.

A central objective of this study is to quantitatively estimate the number of photons that can be detected in this new implementation, the first of such for MPDT investigations. This analysis involves accounting for transmission losses and collection efficiencies at various optical components to determine the photon budget and overall expected experiment sensitivity. This work integrates both the component-level analysis and implementation of the ITS diagnostic system for high-power electric propulsion applications.