Wire-array z-pinch: a powerful x-ray source for ICF

Abstract

The wire-array z-pinch has in a very short time achieved remarkable performance as a powerful (>200 TW), pulsed soft x-ray source of high efficiency (∼15%) and of great relevance to inertial confinement fusion. The underlying physics involves the transformation of wire cores to a plasma corona, the occurrence of uncorrelated axial instabilities, inward flowing low magnetic Reynolds number jets, sometimes an accumulated stable and dynamically confined precursor column, an almost constant velocity implosion when gaps occur in the wire cores and finally at stagnation a fast-rising soft x-ray pulse of typically 5 ns FWHM. Nested arrays improve the performance and can operate in several modes. Three hohlraum designs have been tested; one of these, the dynamic hohlraum, has achieved a radiation temperature of ∼230 eV and has compressed a capsule from 2 to ∼0.8 mm diameter with a neutron yield of > 1010 thermal DD neutrons. Lower mass stainless steel wire arrays are used for Kα radiation sources. Generally implosions lead to more energy radiated than the implosive kinetic energy, and this is hypothesized as being due to ion viscous heating, as fast-growing short wavelength nonlinear MHD instabilities are dissipated; record ion temperatures of 200–300 keV are predicted and have been measured for the stainless steel array on Z at Sandia.