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Title: The role of hot spot mix in the low-foot and high-foot implosions on the NIF

Abstract

Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the “low-foot” class of implosions appears to have been mix. As a result, lower convergence “high-foot” implosions are found to be less susceptible to mix, allowing velocities of >380 km/s to be achieved.

Authors:
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of Rochester, Rochester, NY (United States)
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1369464
Alternate Identifier(s):
OSTI ID: 1361898; OSTI ID: 1378879
Report Number(s):
LLNL-JRNL-713703
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
AC02-76SF00515; AC52-07NA27344; NA0001808
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 42 ENGINEERING; 70 PLASMA PHYSICS AND FUSION

Citation Formats

Ma, T., Patel, P. K., Izumi, N., Springer, P. T., Key, M. H., Atherton, L. J., Barrios, M. A., Benedetti, L. R., Bionta, R., Bond, E., Bradley, D. K., Caggiano, J., Callahan, D. A., Casey, D. T., Celliers, P. M., Cerjan, C. J., Church, J. A., Clark, D. S., Dewald, E. L., Dittrich, T. R., Dixit, S. N., Doppner, T., Dylla-Spears, R., Edgell, D. H., Epstein, R., Field, J., Fittinghoff, D. N., Frenje, J. A., Gatu Johnson, M., Glenn, S., Glenzer, S. H., Grim, G., Guler, N., Haan, S. W., Hammel, B. A., Hatarik, R., Herrmann, H. W., Hicks, D., Hinkel, D. E., Berzak Hopkins, L. F., Hsing, W. W., Hurricane, O. A., Jones, O. S., Kauffman, R., Khan, S. F., Kilkenny, J. D., Kline, J. L., Kozioziemski, B., Kritcher, A., Kyrala, G. A., Landen, O. L., Lindl, J. D., Le Pape, S., MacGowan, B. J., Mackinnon, A. J., MacPhee, A. G., Meezan, N. B., Merrill, F. E., Moody, J. D., Moses, E. I., Nagel, S. R., Nikroo, A., Pak, A., Parham, T., Park, H. -S., Ralph, J. E., Regan, S. P., Remington, B. A., Robey, H. F., Rosen, M. D., Rygg, J. R., Ross, J. S., Salmonson, J. D., Sater, J., Sayre, D., Schneider, M. B., Shaughnessy, D., Sio, H., Spears, B. K., Smalyuk, V., Suter, L. J., Tommasini, R., Town, R. P. J., Volegov, P. L., Wan, A., Weber, S. V., Widmann, K., Wilde, C. H., Yeamans, C., and Edwards, M. J. The role of hot spot mix in the low-foot and high-foot implosions on the NIF. United States: N. p., 2017. Web. doi:10.1063/1.4983625.
Ma, T., Patel, P. K., Izumi, N., Springer, P. T., Key, M. H., Atherton, L. J., Barrios, M. A., Benedetti, L. R., Bionta, R., Bond, E., Bradley, D. K., Caggiano, J., Callahan, D. A., Casey, D. T., Celliers, P. M., Cerjan, C. J., Church, J. A., Clark, D. S., Dewald, E. L., Dittrich, T. R., Dixit, S. N., Doppner, T., Dylla-Spears, R., Edgell, D. H., Epstein, R., Field, J., Fittinghoff, D. N., Frenje, J. A., Gatu Johnson, M., Glenn, S., Glenzer, S. H., Grim, G., Guler, N., Haan, S. W., Hammel, B. A., Hatarik, R., Herrmann, H. W., Hicks, D., Hinkel, D. E., Berzak Hopkins, L. F., Hsing, W. W., Hurricane, O. A., Jones, O. S., Kauffman, R., Khan, S. F., Kilkenny, J. D., Kline, J. L., Kozioziemski, B., Kritcher, A., Kyrala, G. A., Landen, O. L., Lindl, J. D., Le Pape, S., MacGowan, B. J., Mackinnon, A. J., MacPhee, A. G., Meezan, N. B., Merrill, F. E., Moody, J. D., Moses, E. I., Nagel, S. R., Nikroo, A., Pak, A., Parham, T., Park, H. -S., Ralph, J. E., Regan, S. P., Remington, B. A., Robey, H. F., Rosen, M. D., Rygg, J. R., Ross, J. S., Salmonson, J. D., Sater, J., Sayre, D., Schneider, M. B., Shaughnessy, D., Sio, H., Spears, B. K., Smalyuk, V., Suter, L. J., Tommasini, R., Town, R. P. J., Volegov, P. L., Wan, A., Weber, S. V., Widmann, K., Wilde, C. H., Yeamans, C., & Edwards, M. J. The role of hot spot mix in the low-foot and high-foot implosions on the NIF. United States. doi:10.1063/1.4983625.
Ma, T., Patel, P. K., Izumi, N., Springer, P. T., Key, M. H., Atherton, L. J., Barrios, M. A., Benedetti, L. R., Bionta, R., Bond, E., Bradley, D. K., Caggiano, J., Callahan, D. A., Casey, D. T., Celliers, P. M., Cerjan, C. J., Church, J. A., Clark, D. S., Dewald, E. L., Dittrich, T. R., Dixit, S. N., Doppner, T., Dylla-Spears, R., Edgell, D. H., Epstein, R., Field, J., Fittinghoff, D. N., Frenje, J. A., Gatu Johnson, M., Glenn, S., Glenzer, S. H., Grim, G., Guler, N., Haan, S. W., Hammel, B. A., Hatarik, R., Herrmann, H. W., Hicks, D., Hinkel, D. E., Berzak Hopkins, L. F., Hsing, W. W., Hurricane, O. A., Jones, O. S., Kauffman, R., Khan, S. F., Kilkenny, J. D., Kline, J. L., Kozioziemski, B., Kritcher, A., Kyrala, G. A., Landen, O. L., Lindl, J. D., Le Pape, S., MacGowan, B. J., Mackinnon, A. J., MacPhee, A. G., Meezan, N. B., Merrill, F. E., Moody, J. D., Moses, E. I., Nagel, S. R., Nikroo, A., Pak, A., Parham, T., Park, H. -S., Ralph, J. E., Regan, S. P., Remington, B. A., Robey, H. F., Rosen, M. D., Rygg, J. R., Ross, J. S., Salmonson, J. D., Sater, J., Sayre, D., Schneider, M. B., Shaughnessy, D., Sio, H., Spears, B. K., Smalyuk, V., Suter, L. J., Tommasini, R., Town, R. P. J., Volegov, P. L., Wan, A., Weber, S. V., Widmann, K., Wilde, C. H., Yeamans, C., and Edwards, M. J. Thu . "The role of hot spot mix in the low-foot and high-foot implosions on the NIF". United States. doi:10.1063/1.4983625. https://www.osti.gov/servlets/purl/1369464.
@article{osti_1369464,
title = {The role of hot spot mix in the low-foot and high-foot implosions on the NIF},
author = {Ma, T. and Patel, P. K. and Izumi, N. and Springer, P. T. and Key, M. H. and Atherton, L. J. and Barrios, M. A. and Benedetti, L. R. and Bionta, R. and Bond, E. and Bradley, D. K. and Caggiano, J. and Callahan, D. A. and Casey, D. T. and Celliers, P. M. and Cerjan, C. J. and Church, J. A. and Clark, D. S. and Dewald, E. L. and Dittrich, T. R. and Dixit, S. N. and Doppner, T. and Dylla-Spears, R. and Edgell, D. H. and Epstein, R. and Field, J. and Fittinghoff, D. N. and Frenje, J. A. and Gatu Johnson, M. and Glenn, S. and Glenzer, S. H. and Grim, G. and Guler, N. and Haan, S. W. and Hammel, B. A. and Hatarik, R. and Herrmann, H. W. and Hicks, D. and Hinkel, D. E. and Berzak Hopkins, L. F. and Hsing, W. W. and Hurricane, O. A. and Jones, O. S. and Kauffman, R. and Khan, S. F. and Kilkenny, J. D. and Kline, J. L. and Kozioziemski, B. and Kritcher, A. and Kyrala, G. A. and Landen, O. L. and Lindl, J. D. and Le Pape, S. and MacGowan, B. J. and Mackinnon, A. J. and MacPhee, A. G. and Meezan, N. B. and Merrill, F. E. and Moody, J. D. and Moses, E. I. and Nagel, S. R. and Nikroo, A. and Pak, A. and Parham, T. and Park, H. -S. and Ralph, J. E. and Regan, S. P. and Remington, B. A. and Robey, H. F. and Rosen, M. D. and Rygg, J. R. and Ross, J. S. and Salmonson, J. D. and Sater, J. and Sayre, D. and Schneider, M. B. and Shaughnessy, D. and Sio, H. and Spears, B. K. and Smalyuk, V. and Suter, L. J. and Tommasini, R. and Town, R. P. J. and Volegov, P. L. and Wan, A. and Weber, S. V. and Widmann, K. and Wilde, C. H. and Yeamans, C. and Edwards, M. J.},
abstractNote = {Hydrodynamic mix of the ablator into the DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This mix results in increased radiation loss, cooling of the hot spot, and reduced neutron yield. To quantify the level of mix, we have developed a simple model that infers the level of contamination using the ratio of the measured x-ray emission to the neutron yield. The principal source for the performance limitation of the “low-foot” class of implosions appears to have been mix. As a result, lower convergence “high-foot” implosions are found to be less susceptible to mix, allowing velocities of >380 km/s to be achieved.},
doi = {10.1063/1.4983625},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {Thu May 18 00:00:00 EDT 2017},
month = {Thu May 18 00:00:00 EDT 2017}
}

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  • Cited by 4
  • Ignition of an inertial confinement fusion (ICF) target depends on the formation of a central hot spot with sufficient temperature and areal density. Radiative and conductive losses from the hot spot can be enhanced by hydrodynamic instabilities. The concentric spherical layers of current National Ignition Facility (NIF) ignition targets consist of a plastic ablator surrounding 2 a thin shell of cryogenic thermonuclear fuel (i.e., hydrogen isotopes), with fuel vapor filling the interior volume. The Rev. 5 ablator is doped with Ge to minimize preheat of the ablator closest to the DT ice caused by Au M-band emission from the hohlraummore » x-ray drive. Richtmyer–Meshkov and Rayleigh–Taylor hydrodynamic instabilities seeded by high-mode (50 < t < 200) ablator-surface perturbations can cause Ge-doped ablator to mix into the interior of the shell at the end of the acceleration phase. As the shell decelerates, it compresses the fuel vapor, forming a hot spot. K-shell line emission from the ionized Ge that has penetrated into the hot spot provides an experimental signature of hot-spot mix. The Ge emission from tritium–hydrogen–deuterium (THD) and DT cryogenic targets and gas-filled plastic shell capsules, which replace the THD layer with a massequivalent CH layer, was examined. The inferred amount of hot-spot mix mass, estimated from the Ge K-shell line brightness using a detailed atomic physics code, is typically below the 75 ng allowance for hot-spot mix. Furthermore, predictions of a simple mix model, based on linear growth of the measured surface-mass modulations, are consistent with the experimental results.« less
  • Ignition of an inertial confinement fusion (ICF) target depends on the formation of a central hot spot with sufficient temperature and areal density. Radiative and conductive losses from the hot spot can be enhanced by hydrodynamic instabilities. The concentric spherical layers of current National Ignition Facility (NIF) ignition targets consist of a plastic ablator surrounding a thin shell of cryogenic thermonuclear fuel (i.e., hydrogen isotopes), with fuel vapor filling the interior volume [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. The Rev. 5 ablator is doped with Ge to minimize preheat of the ablator closest to the DTmore » ice caused by Au M-band emission from the hohlraum x-ray drive [D. S. Clark et al., Phys. Plasmas 17, 052703 (2010)]. Richtmyer-Meshkov and Rayleigh-Taylor hydrodynamic instabilities seeded by high-mode () ablator-surface perturbations can cause Ge-doped ablator to mix into the interior of the shell at the end of the acceleration phase [B. A. Hammel et al., Phys. Plasmas 18, 056310 (2011)]. As the shell decelerates, it compresses the fuel vapor, forming a hot spot. K-shell line emission from the ionized Ge that has penetrated into the hot spot provides an experimental signature of hot-spot mix. The Ge emission from tritium-hydrogen-deuterium (THD) and deuterium-tritium (DT) cryogenic targets and gas-filled plastic-shell capsules, which replace the THD layer with a mass-equivalent CH layer, was examined. The inferred amount of hot-spot-mix mass, estimated from the Ge K-shell line brightness using a detailed atomic physics code [J. J. MacFarlane et al., High Energy Density Phys. 3, 181 (2006)], is typically below the 75-ng allowance for hot-spot mix [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. Predictions of a simple mix model, based on linear growth of the measured surface-mass modulations, are consistent with the experimental results.« less
  • Hydrodynamic instability growth has been studied using three-dimensional (3-D) broadband modulations by comparing “high-foot” and “low-foot” spherical plastic (CH) capsule implosions at the National Ignition Facility (NIF). The initial perturbations included capsule outer-surface roughness and capsule-mounting membranes (“tents”) that were similar to those used in a majority of implosions on NIF. The tents with thicknesses of 31-nm, 46-nm, and 109-nm were used in the experiments. The outer-surface roughness in the “low-foot” experiment was similar to the standard specification, while it was increased by ~4 times in the “high-foot” experiment to compensate for the reduced growth. The ablation-front instability growth wasmore » measured using a Hydrodynamic Growth Radiography platform at a convergence ratio of 3. The dominant capsule perturbations, generated by the tent mountings, had measured perturbation amplitudes comparable to the capsule thickness with the “low-foot” drive. These tent perturbations were reduced by ~3 to 10 times in implosions with the “high-foot” drive. Unexpectedly, the measured perturbations with initially thinner tents were either larger or similar to the measured perturbations with thicker tents for both “high-foot” and “low-foot” drives. While the measured instability growth of 3-D broadband perturbations was also significantly reduced by ~5 to 10 times with the “high-foot” drive, compared to the “low-foot” drive, the growth mitigation was stronger than expected based on previous “growth-factor” results measured with two-dimensional modulations. Lastly, one of the hypotheses to explain the results is based on the 3-D modulations of the oxygen content in the bulk of the capsule having a stronger effect on the overall growth of capsule perturbations than the outer-surface capsule roughness.« less