Threshold Voltage for Electron Runaway in a Gas Diode with a Needle Cathode

The conditions are analyzed for electron runaway in a gas diode in a strongly inhomogeneous electric field due to the use of a needle cathode. It is shown that the voltage applied to the gap, which is required for electron runaway, tends to a finite value with decreasing radius of the needle tip. An analytical expression is obtained for such a threshold voltage; it is determined only by the gap width and the gas properties.