A method for measuring plasma arc wind tunnel gas velocity with a position controlled electron beam probe

Abstract

An electron beam probe has been used in the Micom 8 MW Plasma Facility. Difficulties in applying the probe to measurements of such parameters as gas density were found to be caused by the weak plasma arc-generated magnetic fields producing positional displacements of the beam. This problem was solved by means of a closed-loop electronic controller. Response time of the controller is down 3 dB at 130 Hz; this was found to be sufficiently fast for adequate control. The operation of the controller indicated that 0·26 G magnetic field was induced in the flow stream by the arc jets. Gas velocity in a plasma flow was estimated by observation of the drift rate of pulsed beam-generated plasma cylinders as a phase shift from two observation points. Estimates of gas velocity for an air flow of 156 g s−1 from phase shift measurements gave 3700±400 m s−1 as compared with a machine computed value of 3800 m s−1 for a normalized specific total enthalpy of 150.

Magnetohydrodynamic velocimetry of a low-pressure plasma jet

“…Yoshikawa et al [4] disturbed the flow with a high-capacitance device. Cason [5] and Girard et al [6] introduced an excess of ions in the jet with an electron-gun, and Gaucherel and Rowe [7] seed the jet with special ionic species, and they both then measure the ion time-offlight by mass spectrometry. Kay [8] used a notched wheel to chop the jet, and a mass spectrometer to get the velocity.…”