Characterisation of a toroidal plasma in a magnetic field by the floating double probe technique for hydrogen

Abstract

In the present work, the floating double probe technique was used to determine the plasma parameters by using the equivalent resistance method [1,2,3,4,5] for hydrogen in toroidal discharge. Measurements were done for transverse and longitudinal positions of the probes to the axial toroidal magnetic field. The experiment was carried out in a 13.56 MHz inductively coupled radio frequency plasma discharge at different pressures of 0.07 torr to 0.20 torr and magnetic fields of 0G to 75G and observed the differences of plasma temperature and particle number density on the discharge axis of the torus. It is also observed that the plasma temperature decreases where as the plasma radial density increases for axial positions but for transverse positions of the probes, the plasma temperature increases and the radial density decreases with the magnetic field and changes with pressure also. The results were compared with nitrogen and argon as well as with direct current glow discharge plasmas with identical input magnetic field [6]. The validity of the probe method for measurement of plasma temperature and density in a toroidal discharge has been discussed.