Experimental study of the ionization region of the highly magnetized RF discharge in argon gas*

We use high-resolution spectroscopy to investigate ionization region of the mini-helicon plasma (MHT) thruster [1]. The ionization region was shown to be just several centimeters long in the Ar discharge [2]. We are using a similar high-resolution MUV-VIS system with improved spectral resolution of about 0.1pm per pixel. It allows capturing Doppler spectra with ~100m/s accuracy for VIS emission lines. The ratios of emission intensities of close ionic and neutral atomic spectral lines are used to determine the ionization region axial structure. Several strong Ar⁺ ion line shapes are collected by angled optical collimators with narrow cones of light collection and numerically analyzed to quantify plasma flow velocities along the MHT discharge.

 

[1] O. Batishchev, Minihelicon Plasma Thruster, IEEE Trans. Plasma Science, 37 (8) 1563 - 1571, August 2009.

[2] T. Matlock, Emission Spectroscopy for the Study of Electric Propulsion Plasmas, MS Thesis, MIT, June 2009.

[3] A. Hyde, O. Batishchev, A high-resolution spectroscopic system for remote measurement of plasma parameters, Review of Sci. Instr. 91(063502), June 2020.