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Title: First beryllium capsule implosions on the National Ignition Facility

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.4948277· OSTI ID:22600249

The first indirect drive implosion experiments using Beryllium (Be) capsules at the National Ignition Facility confirm the superior ablation properties and elucidate possible Be-ablator issues such as hohlraum filling by ablator material. Since the 1990s, Be has been the preferred Inertial Confinement Fusion (ICF) ablator because of its higher mass ablation rate compared to that of carbon-based ablators. This enables ICF target designs with higher implosion velocities at lower radiation temperatures and improved hydrodynamic stability through greater ablative stabilization. Recent experiments to demonstrate the viability of Be ablator target designs measured the backscattered laser energy, capsule implosion velocity, core implosion shape from self-emission, and in-flight capsule shape from backlit imaging. The laser backscatter is similar to that from comparable plastic (CH) targets under the same hohlraum conditions. Implosion velocity measurements from backlit streaked radiography show that laser energy coupling to the hohlraum wall is comparable to plastic ablators. The measured implosion shape indicates no significant reduction of laser energy from the inner laser cone beams reaching the hohlraum wall as compared with plastic and high-density carbon ablators. These results indicate that the high mass ablation rate for beryllium capsules does not significantly alter hohlraum energetics. In addition, these data, together with data for low fill-density hohlraum performance, indicate that laser power multipliers, required to reconcile simulations with experimental observations, are likely due to our limited understanding of the hohlraum rather than the capsule physics since similar multipliers are needed for both Be and CH capsules as seen in experiments.

OSTI ID:
22600249
Journal Information:
Physics of Plasmas, Vol. 23, Issue 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
Country of Publication:
United States
Language:
English

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Three-dimensional simulations of low foot and high foot implosion experiments on the National Ignition Facility journal March 2016
Performance of beryllium targets with full-scale capsules in low-fill 6.72-mm hohlraums on the National Ignition Facility journal May 2017
The potential of imposed magnetic fields for enhancing ignition probability and fusion energy yield in indirect-drive inertial confinement fusion journal June 2017
Capsule physics comparison of National Ignition Facility implosion designs using plastic, high density carbon, and beryllium ablators journal March 2018
Using time-resolved penumbral imaging to measure low hot spot x-ray emission signals from capsule implosions at the National Ignition Facility journal October 2018
Implosion shape control of high-velocity, large case-to-capsule ratio beryllium ablators at the National Ignition Facility journal July 2018
Octahedral spherical Hohlraum for Rev. 6 NIF beryllium capsule journal October 2018
Beryllium capsule implosions at a case-to-capsule ratio of 3.7 on the National Ignition Facility journal October 2018
Probing the seeding of hydrodynamic instabilities from nonuniformities in ablator materials using 2D velocimetry journal September 2018
Implosion performance of subscale beryllium capsules on the NIF journal May 2019
Announcement: The 2018 Ronald C. Davidson Award for Plasma Physics journal May 2019
Modeling and projecting implosion performance for the National Ignition Facility journal December 2018
Sound velocity, shear modulus, and shock melting of beryllium along the Hugoniot journal August 2019
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