Time-resolved observation of the change of electrode shape in single discharge: Rapid self-forming of a thin electrode

A very thin, needlelike electrode can be formed at the tip of thin tungsten electrode by a single discharge with rather high discharge current. We have demonstrated some practical applicability of such very thin electrode. Understanding the formation mechanism of such electrodes is an important issue to utilize the phenomenon to practical applications. We should see what happens on the electrode during the discharge. In this study, the change of electrode shape at tip part of a thin metal electrode induced by single discharge with a large current was observed dynamically by a stroboscopic imaging system with high time resolution. In the imaging system, the second harmonics of a Q-switched neodyum: yttrium-aluminum-garnet laser is used for lighting of charge-coupled device camera and it can take a photo with time resolution of about 10ns. Electrode materials were tungsten and copper of 100μm diameter and the discharge current was 30A with 400μs duration. Both the positive and negative polarities of electro...