大電流単発放電における微細軸形成現象の時間分解観察とその形成ダイナミクス

抄録

Tip of thin tungsten electrode is transformed into a thinner, needle-like shape in single, high current discharge of some tens of amperes and a few hundreds microsecond duration. This self-sharpening phenomenon has been studied by a newly designed, home-made stroboscopic imaging system, which is constructed from a fast CCD camera and a high repetition rate, short pulse laser as an illuminating light source. Using this imaging system, one hundred pictures at 16 or 64 microsecond interval were taken in one discharge event. From these images, we could observe temporal change of the electrode shape during and after the discharge. Special attention was paid on movement of the molten part at the electrode tip. The upper position of the melt part climbs up along the electrode at constant speed after the discharge ended. The move continues for more than one hundred microseconds after the discharge. It is highly probable that the surface tension of the melt is the source of that movement. Based on our observed results, a model of self-sharpening phenomenon has been proposed.