Second derivative of Langmuir probe traces for particle temperature measurements in a magnetized sheet plasma source

Abstract

Hydrogen/argon plasma is produced in a magnetized sheet plasma source. Discharge current is varied from 0.5 A to 2.0 A. I-V characteristics are taken at distances 0 cm to 6 cm from the sheet's plane. The second derivatives of the I-V traces are taken. H⁻ ion and electron temperatures are measured from slope of the logarithm of the plasma current and from the slope of the logarithm of the plasma current's second derivative against the probe potential. Results indicate that electron temperature obtained from d(log I_p) is higher than the electron temperature obtained from d(log I_p"), while for the ion temperature, d(log I_p") gives a higher value.