Pinch formation and the zippering effect in laser-triggered discharge plasma under various electrode separations

In applying a laser-triggered discharge-produced plasma (LT-DPP) as a light source, the most important issues are the supply of fuel and the suppression of a large-scale nonuniformity called the zippering effect. This paper reports pinch formation in LT-DPP under various electrode separations from 4 mm to 10 mm, which provides information for suppressing the zippering effect. Spherically expanding fuel ablated from the cathode becomes visible when the discharge current becomes large. By 100 ns after the laser trigger, the laser-ablated fuel extends 5 mm from the cathode. The width of the fuel reduces gradually with the increase of the current and forms a pinch at the current peak at 200 ns for the case of a 5mm electrode separation. When the electrode separation is larger, neck-like fuel distribution is observed and the pinched portion propagates toward the anode. The condition for reducing the zippering effect is discussed.