129-Chord Time-Resolved Ion Doppler Spectroscopy and Thrust Pendulum Observations in the ECLAIR Experiment at Helicity Space

Helicity Space is developing a fusion based thruster concept which aims to magnetically compress Taylor-State plasmas toward fusion conditions [1]. The ECLAIR experiment models the Helicity Drive using four plasma guns that produce stable helical shear flow jets. A peristaltic magnetic compressor nozzle producing a double pulse magnetic field compresses and further heats the plasma downstream.

We have installed a spectroscopy diagnostic system that includes 8 fiber bundles totaling 129 chords. This allows for temperature and velocity measurements across various regions of the plasma. An ICCD camera takes two frames per plasma shot, giving time resolved measurements of ion line radiation. Results show single gun azimuthal flows and temperatures that vary with gun current. Measurements in the throat region with the nozzle show an increase in ion temperature compared to shots without the nozzle. Prior to setting up a Thomson Scattering system in the future, we plan to estimate electron temperature using line ratios of different ionization states and plasma density from Stark broadening.

A ballistic pendulum installed downstream of the magnetic nozzle measures impulse per plasma pulse. These impulse bits are multiplied by frequency to give effective thrust measurements. Thrust scales favorably with the number of plasma guns. Combining these measurements with exhaust velocity measured by doppler spectroscopy we can calculate specific impulse.

[1] S. You, AIAA Propulsion & Energy, AIAA-2020-3835 (2020)