SNL-Z wire-array initiation experiments at NTF

Abstract

Summary form only given. Plasma formation from SNL-Z-style single and nested W wire arrays is being investigated by driving such arrays with the Zebra pulsed power generator. The load current reaches about 1 MA with 70 ns (10%-90%) rise-time and 10/sup 13/ A/s current rise rate a current waveform similar to the Z machine prepulse. This offers a range of wire array initiation parameters relevant for benchmarking complex simulation codes and improving the predictive capabilities, required for developing larger scale high power X-ray generators. In these experiments the ratio of the current flowing through the inner array to the total load current is measured as a function of time. Gated optical imaging, X-pinch backlighting, streaked optical spectroscopy, UV and EUV spectroscopy, and a variety of laser diagnostics are in different stages of development and fielding on Zebra. The main objective of the NTF wire array experiments is the study of SNL-Z standard single and nested wire arrays initiation to 1 MA current intensity. This includes but is not limited to the individual wires explosion, the plasma formation and early dynamics, the onset and early growth of instabilities, the current division among nested arrays. The early spectrum of perturbations and the diffusion of magnetic field are required inputs for 2D radial-axial MHD computer simulations of wire-array implosions. The experiments also address more complex questions such as the mechanism leading to the inner array heating, and the interaction process between two nested arrays. In an attempt to get information relevant for larger-scale experiments, a wide range of parameters will be explored by modifying in principal the wires nature and conditioning, the array geometry, and the current pulse shape.