The near vacuum hohlraum campaign at the NIF [electronic resource] : A new approach.
The near vacuum campaign on the National Ignition Facility has concentrated its efforts over the last year on finding the optimum target geometry to drive a symmetric implosion at high convergence ratio (30x). As the hohlraum walls are not tamped with gas, the hohlraum is filling with gold plasma an...
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| Online Access: |
Online Access (via OSTI) |
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| Corporate Author: | |
| Format: | Government Document Electronic eBook |
| Language: | English |
| Published: |
Washington, D.C. : Oak Ridge, Tenn. :
United States. National Nuclear Security Administration ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,
2016.
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| Subjects: |
| Summary: | The near vacuum campaign on the National Ignition Facility has concentrated its efforts over the last year on finding the optimum target geometry to drive a symmetric implosion at high convergence ratio (30x). As the hohlraum walls are not tamped with gas, the hohlraum is filling with gold plasma and the challenge resides in depositing enough energy in the hohlraum before it fills up. Hohlraum filling is believed to cause symmetry swings late in the pulse that are detrimental to the symmetry of the hot spot at high convergence. This paper describes a series of experiments carried out to examine the effect of increasing the distance between the hohlraum wall and the capsule (case to capsule ratio) on the symmetry of the hot spot. These experiments have shown that smaller Case to Capsule Ratio (CCR of 2.87 and 3.1) resulted in oblate implosions that could not be tuned round. Larger CCR (3.4) led to a prolate implosion at convergence 30x implying that inner beam propagation at large CCR is not impeded by the expanding hohlraum plasma. A Case to Capsule ratio of 3.4 is a promising geometry to design a round implosion but in a smaller hohlraum where the hohlraum losses are lower, enabling a wider cone fraction range to adjust symmetry. Hohlraum; X-Ray Imaging; Gold; Neutrons; Plasma Temperature. |
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| Item Description: | Published through SciTech Connect. 05/25/2016. Physics of Plasmas 23 5 ISSN 1070-664X; PHPAEN AM. S. Le Pape; L. F. Berzak Hopkins; L. Divol; N. Meezan; D. Turnbull; A. J. Mackinnon; D. Ho; J. S. Ross; S. Khan; A. Pak; E. Dewald; L. R. Benedetti; S. Nagel; J. Biener; D. A. Callahan; C. Yeamans; P. Michel; M. Schneider; B. Kozioziemski; T. Ma; A. G. Macphee; S. Haan; N. Izumi; R. Hatarik; P. Sterne; et al. |
| Physical Description: | Article No. 056311 : digital, PDF file. |