Abstract
Plasma flow velocity was measured by Mach probe (MP) and laser-induced fluorescence (LIF) methods in unmagnetized plasmas with supersonic ion beams. Since the ion gyro-radius was much larger than the probe radius, unmagnetized Mach probe theory was used to determine plasma flow in argon RF plasma with a weak magnetic field (<200 G). In order to determine flow velocities, the Mach probe is calibrated via LIF in the absence of the ion beam, where existing probe theories may be valid although they use different geometries (sphere and plane) and analyzing tools [particle-in-cell (PIC) and kinetic models]. For the comparison of the average plasma flow velocities by MP and LIF, the supersonic ion beam velocity was measured by LIF and then incorporated into a simple formula for average plasma velocity with provisions for background plasma density and beam-corrected electron temperature (Te) measured by a triple probe.
Highlights
Despite the progress of edge physics in fusion research, flow measurements near X-points including E Â B shear velocity and supersonic flow are still under debate.1,2) There is interest in determining the ion velocities in plasma processing and space propulsion systems to support analysis and improve relevant processes
The velocity of the plasmas with ion beams, hvi, is calculated with the assumptions of no strong collisional effects between background plasma and supersonic ion beams using eq (12) with the following parameters: the calibrated in terms of bias voltage (Vb) applied to the ion velocity of the plasma without the ion beam, vp, determined beam source, which is the same as the kinetic velocities of by Mach probe measurements using eq (12); the ion beam the ion beams with beam bias energy of eVb
Plasma flow velocities are measured by a Mach probe (MP) using existing probe theories for the unmagnetized plasmas and are compared to those from the laser-induced fluorescence method with supersonic ion beams
Summary
Despite the progress of edge physics in fusion research, flow measurements near X-points including E Â B shear velocity and supersonic flow are still under debate.1,2) There is interest in determining the ion velocities in plasma processing and space propulsion systems to support analysis and improve relevant processes. Several probe theories for unmagnetized flowing plasmas are available, none of them is prevalent, and there is room for improved determination of flow velocity from Mach probe (MP) measurements. For the Ar ion velocity distribution function, three LIF schemes are available.7) it is possible to calibrate the unmagnetized MP theory with the LIF method. A new theory is introduced in §2 for the determination of electron temperature with an ion beam, especially a supersonic ion beam.
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