Arc radius and resistance measurement of spark gap switch

With a low-inductance experimental apparatus， the arc radius is obtained by photographing the discharge processes of the spark gap switch with high-speed framing camera， and a formula is proposed for calculating the arc radius. The time-dependent arc resistance and conductivity of spark switch gap in the low-inductance circuit are obtained by solving the circuit equation using measured values of current and voltage. The arc radius increases and gradually reaches a saturation value while the discharge channel develops. The radius is 0.6 mm at the peak discharge current of 2.8 kA. The saturation resistance and the time to reach saturation decrease with increasing the peak current of discharge. In addition， the saturation value of arc resistance can be minimized to 0.08 .