Experimental results of radiation-driven, layered deuterium-tritium implosions with adiabat-shaped drives at the National Ignition Facility

Radiation-driven, layered deuterium-tritium (DT) implosions were carried out using 3-shock and 4-shock “adiabat-shaped” drives and plastic ablators on the National Ignition Facility (NIF) [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. The purpose of these shots was to gain further understan...

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Published in:Physics of plasmas 2016-10, Vol.23 (10)
Main Authors: Smalyuk, V. A., Robey, H. F., Döppner, T., Casey, D. T., Clark, D. S., Jones, O. S., Milovich, J. L., Peterson, J. L., Bachmann, B., Baker, K. L., Benedetti, L. R., Berzak Hopkins, L. F., Bionta, R., Bond, E., Bradley, D. K., Callahan, D. A., Celliers, P. M., Cerjan, C., Chen, K.-C., Goyon, C., Grim, G., Dixit, S. N., Eckart, M. J., Edwards, M. J., Farrell, M., Fittinghoff, D. N., Frenje, J. A., Gatu-Johnson, M., Gharibyan, N., Haan, S. W., Hamza, A. V., Hartouni, E., Hatarik, R., Havre, M., Hohenberger, M., Hoover, D., Hurricane, O. A., Izumi, N., Jancaitis, K. S., Khan, S. F., Knauer, J. P., Kroll, J. J., Kyrala, G., Lafortune, K. N., Landen, O. L., Ma, T., MacGowan, B. J., MacPhee, A. G., Mauldin, M., Merrill, F. E., Moore, A. S., Nagel, S., Nikroo, A., Pak, A., Patel, P. K., Ralph, J. E., Sayre, D. B., Shaughnessy, D., Spears, B. K., Tommasini, R., Turnbull, D. P., Velikovich, A. L., Volegov, P. L., Weber, C. R., Widmayer, C. C., Yeamans, C.
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Language:English
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Summary:Radiation-driven, layered deuterium-tritium (DT) implosions were carried out using 3-shock and 4-shock “adiabat-shaped” drives and plastic ablators on the National Ignition Facility (NIF) [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. The purpose of these shots was to gain further understanding on the relative performance of the low-foot implosions of the National Ignition Campaign [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] versus the subsequent high-foot implosions [T. Döppner et al., Phys. Rev. Lett. 115, 055001 (2015)]. The neutron yield performance in the experiment with the 4-shock adiabat-shaped drive was improved by factors ∼3 to ∼10, compared to five companion low-foot shots despite large low-mode asymmetries of DT fuel, while measured compression was similar to its low-foot companions. This indicated that the dominant degradation source for low-foot implosions was ablation-front instability growth, since adiabat shaping significantly stabilized this growth. For the experiment with the low-power 3-shock adiabat-shaped drive, the DT fuel compression was significantly increased, by ∼25% to ∼36%, compared to its companion high-foot implosions. The neutron yield increased by ∼20%, lower than the increase of ∼50% estimated from one-dimensional scaling, suggesting the importance of residual instabilities and asymmetries. For the experiment with the high-power, 3-shock adiabat-shaped drive, the DT fuel compression was slightly increased by ∼14% compared to its companion high-foot experiments. However, the compression was reduced compared to the lower-power 3-shock adiabat-shaped drive, correlated with the increase of hot electrons that hypothetically can be responsible for reduced compression in high-power adiabat-shaped experiments as well as in high-foot experiments. The total neutron yield in the high-power 3-shock adiabat-shaped shot N150416 was 8.5 × 1015 ± 0.2 × 1015, with the fuel areal density of 0.90 ± 0.07 g/cm2, corresponding to the ignition threshold factor parameter IFTX (calculated without alpha heating) of 0.34 ± 0.03 and the yield amplification due to the alpha heating of 2.4 ± 0.2. The performance parameters were among the highest of all shots on NIF and the closest to ignition at this time, based on the IFTX metric. The follow-up experiments were proposed to continue testing physics hypotheses, to measure implosion reproducibility, and to improve quantitative understanding on present implosion results.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4964919