Plasma-facing tests of Helicity Space's Peristaltic Magnetic Compressor-Expander Nozzle*

Helicity Space is developing a fusion-based thruster concept which aims to magnetically compress Taylor-State plasmas toward fusion conditions [1]. The thruster incorporates a magnetic nozzle that traps the target plasma and, like a Laval nozzle, has a compression and expansion section. The nozzle consists of an array of Bitter coils connected as a transmission line with varying inductance and constant capacitance [2]. Sending two suitably timed current pulses into the nozzle results in a traveling magnetic mirror that peristaltically compresses the trapped plasma. The expansion section reverses the process to cool the exhaust and generate thrust.

The nozzle is driven by two independent, SCR-switched capacitor banks, and is undergoing high-power tests for integration into the ECLAIR experiment [3]. We present the following results: (i) B-dot array measurements of magnetic field propagation along the nozzle and matching analytical and numerical calculations; (ii) the status of attempts to visualize the evolution of the magnetic flux surfaces with a thermionic emitter in a He background gas [4]; (iii) results from plasma-facing tests on a single coil to inform our choice of shielding material to minimize the risk of damage to the nozzle; (iv) results from 3D MHD simulations of four jets entering the nozzle to demonstrate how the timing of the jets with the nozzle fields affect plasma stability; (v) an initial suite of diagnostics to measure temperature and density of the plasma before and after compression [5].