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Title: Short-Wavelength Perturbation Growth Studies for NIF Double-Shell Ignition Target Designs

Abstract

A major challenge in achieving ignition with double-shells is controlling the mix of the dense, high-Z pusher into the DT gas. During implosion, interface perturbations become unstable as they are subjected to either impulsive (Richtmyer-Meshkov) or time-dependent (Rayleigh-Taylor) accelerations. These processes are especially critical for double-shells since density gradient stabilization mechanisms (that play a key role in the baseline cryogenic target) are not present. To study the nonlinear RT evolution for such a large range in modes we use the parallel 3-D rad-hydro code HYDRA. Simulations have revealed a new pathway for the RT instability of perturbations on the outer surface of the inner shell leading to shell disruption. We demonstrate that this instability can be controlled by tamping the inner shell with a low-Z material but it is not entirely suppressed. We find that the pusher/tamper interface transitions to turbulence at late times with large Reynolds number but still the integrity of the pusher is maintained. Furthermore, numerical studies suggest that for perturbations with mode numbers (l > 600), the mix-width at the pushed tamper interface approaches a constant value. Finally, to avoid turbulence onset altogether we investigate a new pusher with an imprinted density-gradient scale length in combinationmore » with a CuO/Cu{sub 2}O foam. Preliminary 2-D simulations with mode numbers up tp l = 612 show virtually no growth in this design.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15005403
Report Number(s):
UCRL-JC-151999
TRN: US0305370
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: IFSA Conference, Monterey, CA (US), 09/07/2003--09/12/2003; Other Information: PBD: 22 Aug 2003
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; US NATIONAL IGNITION FACILITY; DESIGN; IGNITION; INSTABILITY; REYNOLDS NUMBER; STABILIZATION; TARGETS; DEUTERIUM; TRITIUM; DISTURBANCES; H CODES; COMPUTERIZED SIMULATION

Citation Formats

Milovich, J L, Amendt, P, Marinak, M, and Robey, H. Short-Wavelength Perturbation Growth Studies for NIF Double-Shell Ignition Target Designs. United States: N. p., 2003. Web.
Milovich, J L, Amendt, P, Marinak, M, & Robey, H. Short-Wavelength Perturbation Growth Studies for NIF Double-Shell Ignition Target Designs. United States.
Milovich, J L, Amendt, P, Marinak, M, and Robey, H. Fri . "Short-Wavelength Perturbation Growth Studies for NIF Double-Shell Ignition Target Designs". United States. https://www.osti.gov/servlets/purl/15005403.
@article{osti_15005403,
title = {Short-Wavelength Perturbation Growth Studies for NIF Double-Shell Ignition Target Designs},
author = {Milovich, J L and Amendt, P and Marinak, M and Robey, H},
abstractNote = {A major challenge in achieving ignition with double-shells is controlling the mix of the dense, high-Z pusher into the DT gas. During implosion, interface perturbations become unstable as they are subjected to either impulsive (Richtmyer-Meshkov) or time-dependent (Rayleigh-Taylor) accelerations. These processes are especially critical for double-shells since density gradient stabilization mechanisms (that play a key role in the baseline cryogenic target) are not present. To study the nonlinear RT evolution for such a large range in modes we use the parallel 3-D rad-hydro code HYDRA. Simulations have revealed a new pathway for the RT instability of perturbations on the outer surface of the inner shell leading to shell disruption. We demonstrate that this instability can be controlled by tamping the inner shell with a low-Z material but it is not entirely suppressed. We find that the pusher/tamper interface transitions to turbulence at late times with large Reynolds number but still the integrity of the pusher is maintained. Furthermore, numerical studies suggest that for perturbations with mode numbers (l > 600), the mix-width at the pushed tamper interface approaches a constant value. Finally, to avoid turbulence onset altogether we investigate a new pusher with an imprinted density-gradient scale length in combination with a CuO/Cu{sub 2}O foam. Preliminary 2-D simulations with mode numbers up tp l = 612 show virtually no growth in this design.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {8}
}

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