Combined Langmuir probe, electrical and hybrid modelling characterization of helium glow discharges

We present a systematic study of electrical characteristics and Langmuir probe measurements on plane-parallel electrode helium glow discharges operated in normal and abnormal glow regimes. The experimental studies are complemented with numerical modelling based on a hybrid approach combining fluid and particle descriptions of the discharge plasma. A comparison between the experimental data and the two-dimensional modelling results is presented. The temperature of slow Maxwellian electrons is found to be ≈0.055 eV in the negative-glow region nearly independent of the discharge conditions. This temperature value is used as an input parameter of the hybrid model. Good agreement is obtained between the calculated spatial density distribution of electron impact excitation events and the CCD image of the light emission from the discharge. The calculated electron densities are 1.3–2 times higher than the corresponding Langmuir probe data; the possible reason for these differences is discussed.