Collision of Ionization Waves in Long Discharge Tubes

TL;DR

This study investigates the collision behavior of ionization waves in long discharge tubes filled with neon or argon, revealing how their interaction affects wave propagation, emission, and suppression zones under various conditions.

Contribution

It provides new insights into ionization wave interactions, especially the collision dynamics and suppression zones in long discharge tubes with different gases and voltages.

Findings

Ionization waves slow down and degrade upon collision.

A suppression zone near the tube center depends on voltage and gas type.

Memory effects influence wave stability at high repetition rates.

Abstract

This research focuses on interaction of ionization waves (IW) generated in long discharge tubes (1 m length and 1.5 cm in diameter) filled with neon or argon under pressure about 1 Torr and, in particular, on simplest case of such interference which is collision of the opposite directed IW of positive polarity. The waves were triggered from two electrodes of the tube by simultaneous application of the same high voltage pulse and propagated toward the tube center until their collision. Space and time stability of the collisions was achieved via decreasing time delay of the initial breakdowns which trigger IW by employment of both memory effect and photo-desorption of wall surface electrons. Significant memory effect occurred for the pulse repetition rate over 100Hz. Multiple IW transition from the electrode forms specific one-electrode discharge; as a result the problem of IW collision was transformed into the observation of two opposite one-electrode discharges interaction. Patterns of IW interfering were registered via deviation of their kinematic characteristics (x-t diagrams) from ones for non-collided wave. This method shows that two ionization waves travel toward each other with decreasing speeds and subsequent degradation of the emission. An area near the tube center where IWs emission was not detected was considered as the IW suppression zone. The zone width depends on voltage amplitude, gas type and pressure.