We have derived a 3-dimensional synthetic model for NIF implosion conditions, by predicting and optimizing fits to a broad set of x-ray and nuclear diagnostics obtained on each shot. By matching ...x-ray images, burn width, neutron time-of-flight ion temperature, yield, and fuel rhor, we obtain nearly unique constraints on conditions in the hotspot and fuel in a model that is entirely consistent with the observables. This model allows us to determine hotspot density, pressure, areal density (rhor), total energy, and other ignition-relevant parameters not available from any single diagnostic. This article describes the model and its application to National Ignition Facility (NIF) tritium-hydrogen-deuterium (THD) and DT implosion data, and provides an explanation for the large yield and rhor degradation compared to numerical code predictions.
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 the data collected and measurements made to date. Data form directly driven, DT filled microballoons, as well as, indirectly driven, cryogenically layered ignition experiments are presented. The data presented show that the primary cores from directly driven implosions are approximately twice as large, 64 {+-} 3 {mu}m, as indirect cores 25 {+-} 4 and 29 {+-} 4 {mu}m 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.
A micro-channel plate based temporally-gated x-ray camera (framing camera) is one of the most versatile diagnostic tools of inertial confinement fusion experiments; particularly for observation of ...the shape of x-ray self emission from compressed core of imploded capsules. However, components used in an x-ray framing camera have sensitivity to neutrons induced secondary radiations. On early low-yield capsule implosions at the National Ignition Facility (NIF), the expected neutron production is about 5 x 10{sup 14}. Therefore, the expected neutron fluence at a framing camera located {approx} 150 cm from the object is 2 x 10{sup 9} neutrons/cm{sup 2}. To obtain gated x-ray images in such harsh neutron environments, quantitative understanding of neutron-induced backgrounds is crucial.
Velocity interferometer system for any reflectors (VISARs), are becoming increasingly popular in the measurement of shock waves in solids and liquids. VISAR techniques are used in measurements of ...transit time, speed of shock waves in flight in transparent media L. C. Chhabildas and J. L. Wise, in Proceedings of the 4th APS Topical Conference on Shock Waves in Condensed Matter, Spokane, Washington, 1985, edited by Y. M. Gupta (Plenum, New York, 1986); P. M. Celliers et al., Appl. Phys. Lett. 73, 1320 (1998), and in measurements of particle velocity. However, in cases where shock compression or release may change the index of refraction n+ik of the material being studied, the VISAR technique must be applied with care. Changes in n and k introduce phase shifts into the VISAR results that are not associated with changes in velocity. This paper presents a derivation of the theoretical output of a line VISAR that includes the effects of changing n and k and an experimental observation of a non-Doppler shift related effect.
The Atlas High-Energy Density Physics Project Davis, Harold A.; Keinigs, Rhon K.; Anderson, Wallace E. ...
Japanese Journal of Applied Physics,
02/2001, Letnik:
40, Številka:
2S
Journal Article
Recenzirano
Atlas is a pulsed-power facility under development at Los Alamos National Laboratory to drive high-energy density experiments. Atlas will be operational in the summer of 2000 and is optimized for the ...study of dynamic material properties, hydrodynamics, and dense plasmas under extreme conditions. Atlas is designed to implode heavy-liner loads in a z-pinch configuration. The peak current of 30 MA is delivered in 4 µs. A typical Atlas liner is a 47-gram-aluminum cylinder with ∼4-cm radius and 4-cm length. Three to five MJ of kinetic energy will be delivered to the load. Using composite layers and a variety of interior target designs, a wide variety of experiments in ∼cm
3
volumes will be performed. Atlas applications, machine design, and the status of the project are reviewed.
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