Abstract
First results from the analysis of neutron image data collected on implosions of cryogenically layered deuterium-tritium capsules during the 2011-2012 National Ignition Campaign are reported. The data span a variety of experimental designs aimed at increasing the stagnation pressure of the central hotspot and areal density of the surrounding fuel assembly. Images of neutrons produced by deuterium–tritium fusion reactions in the hotspot are presented, as well as images of neutrons that scatter in the surrounding dense fuel assembly. The image data are compared with 1D and 2D model predictions, and consistency checked using other diagnostic data. The results indicate that the size of the fusing hotspot is consistent with the model predictions, as well as other imaging data, while the overall size of the fuel assembly, inferred from the scattered neutron images, is systematically smaller than models' prediction. Preliminary studies indicate these differences are consistent with a significant fraction (20%–25%) of the initial deuterium-tritium fuel mass outside the compact fuel assembly, due either to low mode mass asymmetry or high mode 3D mix effects at the ablator-ice interface.
Highlights
The goal of indirectly driven inertial confinement fusion experiments at the National Ignition Facility (NIF) is to obtain thermonuclear ignition using a small mass, $170 lg, of hydrogen isotopes.1 The process begins with the 192 beam, 351 nm, NIF laser which illuminates a high-Z cavity producing a flux of soft X-rays
III, we describe a simple 1D model of the fuel assembly, based on neutron imaging data, and define the geometric down scatter ratio (DSR)
IV, we report on image data collected during 2012 ignition experiments and compare these data with the 1D model, as well as 2D post-shot simulations
Summary
The goal of indirectly driven inertial confinement fusion experiments at the National Ignition Facility (NIF) is to obtain thermonuclear ignition using a small mass, $170 lg, of hydrogen isotopes. The process begins with the 192 beam, 351 nm, NIF laser which illuminates a high-Z cavity (hohlraum) producing a flux of soft X-rays. The process begins with the 192 beam, 351 nm, NIF laser which illuminates a high-Z cavity (hohlraum) producing a flux of soft X-rays These X-rays ablate the outer surface of a $2 mm diameter plastic shell, or ablator, containing a cryogenically formed deuterium-tritium ice shell approximately 70 lm thick. Results from ignition experiments performed between December 2011 and September 2012, referred to below as the 2012 data set, are reported here. These results focus on nuclear performance with emphasis on the size and shape of the implosion using the neutron imaging diagnostic..
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