Abstract
A summary of data and results from the first neutron images produced by the National Ignition Facility (NIF), Lawrence Livermore National Laboratory, Livermore, CA, USA are presented. An overview of the neutron imaging technique is presented, as well as a synopsis of data and measurements made to date. Data from directly driven, DT filled microballoons, as well as indirectly driven, cryogenically layered ignition experiments are presented. The data show that the primary cores from directly driven implosions are approximately twice as large, 64 ± 3m, as indirectly driven cores, 25 ± 4 and 29 ± 4m and more asymmetric, P2/P0 = 47% vs. −14% and 7%. Further, comparison with the size and shape of X-ray image data on the same implosions show good agreement, indicating X-ray emission is dominated by the hot regions of the implosion.
Highlights
The National Ignition Facility has begun the quest to systematically determine the conditions necessary to ablatively drive a cryogenically layered DT filled capsule to the pressures and temperatures necessary to induce thermonuclear burn, with the goal of obtaining energetic break-even
The first neutron image data produced by the National Ignition Facility (NIF) neutron imaging diagnostic is presented
Neutrons are detected in a 170 mm × 170 mm × 5 cm volume of coherently arrayed, 250 m diameter, BCF99-55 scintillating fibers positioned 2800 cm from the target. Light from this volume is collected in two digital recording systems, electro-optically gated on neutron flight times corresponding to energy gates of 10–12 MeV and 13–17 MeV
Summary
The National Ignition Facility has begun the quest to systematically determine the conditions necessary to ablatively drive a cryogenically layered DT filled capsule to the pressures and temperatures necessary to induce thermonuclear burn, with the goal of obtaining energetic break-even. Images of where fusion neutrons are produced and scattered within the highly compressed fuel assembly provide key information on the efficiency of the implosion. This information, when combined with other data, such as ion temperature, yield, bang-time, etc, can be used to provide a detailed picture of the burning plasma and the material surrounding it, allowing measurements of fuel volume, areal density, pressure, adiabat, etc.
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