Diagnosis for the Interaction of Supersonic Molecular Beam with Plasma

Abstract

Supersonic Molecular Beam Injection (SMBI) is a new fuelling method for Tokamaks and has recently been improved to enhance the flux of the beam and to make a survey of the cluster effect within the beam. There are a series of new phenomena, which implicate the interaction of the beam (including clusters) with the toroidal plasma of HL-1M Tokamak. The Hα signals from the edge show a regular variation around the torus. Around the injection port, the edge Hα signals are positive rectangular wave, which is consistent with that of the injection beam pulses. The edge electron temperature, measured with movable Langmuir probes, decreases by an order of magnitude and the density increases by an order of magnitude. Hα emission at the beam injection port, measured with CCD camera at an angle of 13.4 degrees to the SMBI line, shows many separate peaks within the contour plot. These peaks may show the strong emission produced by the interaction of the hydrogen clusters with the plasma. Hydrogen clusters may be produced in the beam according to the empirical scaling (Hagena) law of clustering onset, Γ* = kd0.85P0/T02.29. Here d is the nozzle diameter in μm, P0 the stagnation pressure in mbar, T0 the source temperature in K, and k is a constant related to the gas species. If Γ* > 100, clusters will be formed. In present experiment Γ* is about 127.