Townsend discharge in nitrogen at low temperatures: enhanced noise and instability due to electrode phenomena

Abstract

The temperature dependence of the properties of the low-current Townsend discharge in nitrogen is studied. The experiments are carried out on a device with a high-resistivity semiconductor electrode in the temperature range 85–292 K at a current density not exceeding 25 μA cm−2. The discharge gap of the device is 0.85 mm, while the nitrogen density corresponds to the gas pressure Pa (49.5 Torr) at T = 292 K. The earlier increase found in the discharge sustaining voltage in time at a fixed current is quantitatively investigated for the cryogenic discharge. The relaxation is accompanied by transitions to new discharge states with an increased noise intensity. The characteristic time of the relaxation is hundreds of seconds. The effect is especially pronounced in the range of 100–150 K and is relatively weak at room temperature. The interpretation of the experimental data is based on the hypothesis that considers the formation of neutral aggregates of nitrogen in the form [(N2)n]− in the discharge volume. The condensation of the clusters on the cathode leads to a change in its emission properties, which changes the properties of the discharge.