The Los Alamos deuterium fiber high density Z pinch experiment

The deuterium fiber high density Z pinch at Los Alamos is a linear Z pinch run as near as possible in radial equilibrium. The plasma is formed from a fiber of solid deuterium ice, and the plasma density is maintained near solid density. Although magnetically confined, the parameters of this plasma are much closer to those encountered in inertial confinement fusion than in toroidal magnetic fusion. The magnetic confining field in present experiments exceeds a megagauss, and in the next generation of experiments beginning this year at Los Alamos (and in similar ones at NRL) they may exceed 100 megagauss. Such a linear Z pinch with purely azimuthal field is predicted by MHD theory to be unstable to m=0 and m=1 modes, with growth rates comparable to the thermal velocity. In contrast to these predictions, experimental results show stability for 100-200 growth times. Maintenance of equilibrium during the heating phase of such a pinch requires that the current follow a prescribed time history. A simple model of the heating process predicts that the current should rise rapidly to a megampere and continue more slowly to the Pease current of about 1.4 MA, where steady state equilibrium is possible. Deficiencies are being addressed by a new experiment at Los Alamos, the Zebra 1.2 MA Fiber A pinch. A new generator operating at 3 MV feeding a vertical water transmission line will provide current rising to 1.2 MA in 100 ns in a 5 cm fiber pinch. The generator design, the experimental arrangement and the initial experiments on the Zebra device are described. Experiments have continued on the 250 kA experiment during construction. A CCD-based shlieren microscope has been developed with a spatial resolution of 4 μm and the ability to make two 150 ps exposures separated by 10 ns. This diagnostic and results are described