Electrical Discharge Path Induced by Pulsed Nd:YAG Laser Plasma in DC Air Gap of Metal Rod-to-Water Electrodes

By using a metal rod-to-water electrode, we studied the properties of electrical discharge paths induced by a visible laser beam, which is a pulsed Nd:YAG laser beam with a wavelength of lambda = 532 nm, in an air gap with a nonuniform DC electric field. The discharge paths are classified into guiding and triggering types, where the former is defined as the path across the plasma region, and the latter refers to the paths excluding the former one. We succeeded in capturing the time-integrated image for the discharge path induced along or around the light axis of the pulsed YAG laser. From the results of the experiments, it is inferred that the luminous plasma produced by a pulsed YAG laser can guide or trigger the discharge path, and the nonluminous plasma region along the light axis of the laser beam has the capability to induce a discharge path. A weakly ionized channel was produced as in the case of an ultraviolet laser.