Investigation of a Dynamic Corona to Normal Glow Transition in a Neon Gas Diode

The development of the spatial distribution of the emitted lights from a gas diode during the positive corona to normal glow discharge transition is investigated. The diode consists of a rod anode and a cylinder cathode and is filled with neon at a pressure of 1.33 mbar. Investigations are performed both in the dynamic and stationary regimes. In the dynamic regime, the slowly increasing voltage is applied to the diode, and the time development of the emitted light from the different positions in the diode is measured. In the stationary regime, the slowly increasing applied voltage is restituted with the stepping voltage, which allowed a series of stationary regimes with different values of current to be established (from 5 nA to 10 $\mu\hbox{A}$ ). The intensity of the emitted light from the different positions in the diode along the diode axes is measured by a scanning technique, starting from the anode up to the space behind the cathode with a 0.1-mm precision. These distributions are compared with the corresponding photographic records of the emitted lights from the diode to confirm the spatial distributions of the emitted lights. The results of these investigations show that the light emission for the smallest detected current (from 5 to 100 nA) is ordinate near the anode surface and that this kind of discharge should be defined as the positive corona. With the increase in the current, the conduction channel to the cathode is made because of the discharge transfer from the corona to the normal glow for current values of about 1 $\mu\hbox{A}$. The real-time measurement shows that, in the present condition, corona appears and vanishes in about 2 ms and that the transition to the stationary normal glow is about 10 ms. The increase in the emitted light that was detected corresponds to the second and third stages of the normal glow discharge formation in the gas diode when the initial breakdown channel appears, grows, and changes up to the final stationary discharge regime.