Neutron Production from Z-pinch Plasmas at the 1 MA Zebra Generator
AuthorMcKee, Erik Scott
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Neutrons produced deuterium Z-pinch plasmas are widely acknowledged to be aconsequence of highly accelerated deuterons undergoing nuclear fusion with relativelystationary deuterons . The acceleration is thought to occur in intense fields createdin the MHD instabilities that punctuate the plasma column. Interestingly, the energiesof the accelerated ions exceed the applied voltage across the electrode gap. Weuse the 1 MA Zebra pulsed-power generator at the Nevada Terawatt Facility (NTF)to explore this poorly understood fast neutron production mechanism by creatingdeuterium Z-pinches in three distinct types of target loads. The loads are a cylindricalshell of deuterium gas, the far less explored deuterided palladium wire arrays, and adeuterium-carbon ablated laser plume target, which is unique to the NTF.The pinch dynamics vary considerably in these three targets and provide theopportunity to explore the ion acceleration mechanism. We infer the characteristics ofthe accelerating fields from a wide range of diagnostic data including the neutron yield,energy spectrum and angular distribution, and the properties of the matching electronbeams that are accelerated in the same field, and the energetic X-rays they produceon stopping. The plasma and the instabilities were recorded on several high-speedimaging diagnostics along with time-integrated soft (<10 keV) X-ray pinhole images.The three load types produced total neutron yields in the 10^8-10^10 n/pulse range. Thesynchronization we observe between the ion and electron beams and the developmentof instabilities leads us to conrm the acceleration hypothesis. We also present thecharacteristics of the fields and ion beams in these varied pinches.