Dwell times of exploding tungsten wires in air

Abstract

The paper deals mainly with the voltage dependence of the dwell times of 130-mm-long tungsten wires with diameters of 0.05, 0.10, 0.15, and 0.20 mm. The results of the measurements reported show that tungsten wires have dwell times of only the short type, that the restrikes are always initiated at the exterior of the wires, and that during the dwell times tungsten wires have higher conductivity than copper or constantan wires. At low voltages the dwell times increase with increasing wire diameter. However, above 10 kV the dwell times within the range of experimental error are equal for all the diameters examined. A comparison with the results obtained from exploding copper wires with the same diameter shows that at low voltages the short dwell times of the copper wires are shorter than those of the tungsten wires and that at higher voltages the dwell times of the tungsten wires become much shorter than those of the copper wires, decreasing monotonically with increasing voltage. The special features of the exploding wires during the dwell times and the restrike phase are illustrated by films made by a rotating-mirror streak camera, a camera with a Kerr-cell shutter, and an image-converter camera.