Spatial distribution of electric field strength in dielectric barrier discharge in helium is determined from the Stark splitting and shifting of two visible helium lines and their forbidden components. Electric field is calculated by using spectral distance between forbidden and allowed components and results are compared to those obtained by using forbidden/allowed intensity ratio. Distributions of electric field, obtained for 200 and 800mbar pressures, are typical for the glow mode of the discharge.

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Time–space-resolved optical emission spectroscopy was used for the investigation of a diffuse dielectric barrier discharge (DBD) in helium and in 95%He + 5%H2 gas mixture. The DBD in helium was diffuse in the whole range of the applied voltage, while in the gas mixture the discharge operated in diffuse mode only in the regime with more than three current peaks. In the helium discharge, the excitation of hydrogen H β is delayed compared with the excitation of the helium atomic line, while in the gas mixture both lines are excited simultaneously. Using the Stark polarization spectroscopy technique based on the He I 492.19 nm line and its forbidden counterpart, the electric field distribution (EFD) was measured in the cathode region of the DBD in helium and in the helium–hydrogen mixture. Electric field space distributions in both gas discharges, obtained at 20 kPa pressure, showed linear decreasing in the cathode region, which is a typical characteristic of the glow discharge. Linear fits of the EFDs showed that the length of the cathode fall region is smaller in the gas mixture than in pure helium. In the multiple current peak mode of the DBD, EFD was measured during each of the three current peaks and no noticeable difference between them is observed.

In this paper the diffuse dielectric barrier discharge in helium was investigated using electrical measurements and time–space resolved optical emission spectroscopy. Electric field strength was measured using Stark polarization emission spectroscopy. Investigations were performed at 200 and 800 mbar pressures. It was found that the electric field strength was higher at the higher pressure while cathode fall length was shorter. During the whole discharge development period the length of the cathode fall region decreases. An interesting result is that in the period of current decrease, the maximum of the electric field distribution shifts away from the cathode showing the accumulation of negative charge near the cathode surface.

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