Electron and ion instabilities in diodes

• DOI: 10.1007/bf02750667
• Publication Date: 2007-12-18T15:07:27Z
• Authors: V. C. Boffi; V. G. Molinari; D. E. Parks; R. Scozzafava

In this paper criteria for the stability of a collisionless plane diode containing an uniform density of infinitely heavy ions in the interelectrode space are obtained. All electrons are assumed to be emitted from the cathode of the diode with a single velocity and every emitted electron is finally absorbed at the collector surface. Thus although the theory applies only in the case where there are no reflected currents, it does take account of potential inhomogeneities induced by space charge. The stability criterion is obtained in the form of an exponential polynomial. We have studied this polynomial in detail for the case of a diode without a neutralizing positive ion background, thereby extracting from the theory a very simple stability criterion. The result has been applied, to the case of a diode operating at short circuit. In the final part of the paper we study ion instabilities. In this case we have been able to obtain directly useful results only for the case of a diode in which the space charge is completely neutralized.