Langmuir probe measurements of the electron energy distribution function in magnetized gas discharge plasmas

Abstract

In this work, methods for using Langmuir probes (LPs) in magnetized plasmas are presented. The electron part of the current–voltage probe characteristics is used to obtain the plasma potential, the electron energy distribution function (EEDF), the electron temperature and the electron density. The application of LPs to EEDF evaluation in the presence of magnetic fields in the range 0.01–0.1 T is investigated and discussed based on kinetic theory in a non-local approach. Data for EEDFs in magnetic fields in the range 0.015–0.079 T are acquired using current–voltage characteristics measured in low pressure Ar and He dc gas discharges. It is also shown that the EEDFs are Maxwellian up to the energy of the first excited states of argon and helium. The values of the plasma potential, electron temperature and density are evaluated. Comparison of the results obtained with probes perpendicular and parallel to the magnetic field results in satisfactory agreement.