Current Buildup in Neon Gas Discharges at Small Overvoltages

This work deals with the manner in which current increases in a slightly overvolted neon discharge. The increase is exponential with a time constant θ. It is assumed that the discharge is sustained entirely by secondary emission from the cathode and that this emission is caused by Ne⁺ ions and neon atoms excited to a metastable state. The model contains no adjustable parameters. Although most of the secondary emission is caused by ions, the metastables are dominant in controlling the buildup of current. The theory which is developed is valid for overvoltages ΔV small enough so that θ is large compared to the diffusion time of the metastables. Under these conditions the product θΔV is constant. The rate of buildup has been observed as a function of overvoltage in a plane parallel discharge tube with movable electrodes. Over the range 1.5<p₀d<11 cm-mm Hg the buildup is observed to occur on the average 15% faster than calculated.