Messung der von Elektronenlawinen erzeugten Raumladungsfelder mittels einer Sondenlawine

Abstract

The electrical fields due to the space charge of positive ions in a plane-parallel discharge gap are measured by means of an electron avalanche. The measurements were made in a N₂-CH₄ gas mixture (5% CH₄) at a total pressure of 210 Torr (20 °C) in a 3 cm gap, at a voltage U<U_D (static breakdown potential). The positive ions are produced by electron avalanches, which are released from a broad area by an UV flash at the cathode. The ions so produced drift towards the cathode with a drift velocity v₊. After a timeT the probe avalanche is started by a second UV flash in the symmetry axis of the charge distribution. From its temporal growth, which is given by the relation$i_s (t) \sim \delta v\_\exp \left( {\int\limits_0^t {\alpha v\_dt} } \right)$, one can evaluate the space charge field E(z) of the positive ions. The measured fields are in good agreement with those predicted by calculations.