Effect of current prepulse on wire array initiation on the 1-MA ZEBRA accelerator

Abstract

Experiments on the 1-MA ZEBRA accelerator with reduced current prepulse duration, using a flashover switch, demonstrate a significant increase of initial energy deposition into the tungsten wire array before breakdown, and of total radiation energy from the Z pinch. Shorter current prepulse raises the current rate through each individual wire in the array and results in an increase of the energy deposition into wire cores before breakdown. In our experiments, the inferred tungsten wire temperature increases from ∼800K (with 250ns prepulse) up to ∼3700K (with 60ns prepulse). Total radiation energy increases from 12 to 16kJ. Our experimental results relate wire-array initiation to heating of the individual array wires up to the time of breakdown.