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Transition from Collisional to Collisionless Regimes in Interpenetrating Plasma Flows on the National Ignition Facility

Author(s): Ross, JS; Higginson, DP; Ryutov, D; Fiuza, F; Hatarik, R; et al

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Abstract: A study of the transition from collisional to collisionless plasma flows has been carried out at the National Ignition Facility using high Mach number (M>4) counter streaming plasmas. In these experiments, CD-CD and CD-CH planar foils separated by 6–10 mm are irradiated with laser energies of 250 kJ per foil, generating ∼1000  km/s plasma flows. Varying the foil separation distance scales the ion density and average bulk velocity and, therefore, the ion-ion Coulomb mean free path, at the interaction region at the midplane. The characteristics of the flow interaction have been inferred from the neutrons and protons generated by deuteron-deuteron interactions and by x-ray emission from the hot, interpenetrating, and interacting plasmas. A localized burst of neutrons and bright x-ray emission near the midpoint of the counter streaming flows was observed, suggesting strong heating and the initial stages of shock formation. As the separation of the CD-CH foils increases we observe enhanced neutron production compared to particle-in-cell simulations that include Coulomb collisions, but do not include collective collisionless plasma instabilities. The observed plasma heating and enhanced neutron production is consistent with the initial stages of collisionless shock formation, mediated by the Weibel filamentation instability.
Publication Date: 5-May-2017
Electronic Publication Date: 5-May-2017
Citation: Ross, JS, Higginson, DP, Ryutov, D, Fiuza, F, Hatarik, R, Huntington, CM, Kalantar, DH, Link, A, Pollock, BB, Remington, BA, Rinderknecht, HG, Swadling, GF, Turnbull, DP, Weber, S, Wilks, S, Froula, DH, Rosenberg, MJ, Morita, T, Sakawa, Y, Takabe, H, Drake, RP, Kuranz, C, Gregori, G, Meinecke, J, Levy, MC, Koenig, M, Spitkovsky, A, Petrasso, RD, Li, CK, Sio, H, Lahmann, B, Zylstra, AB, Park, H-S. (2017). Transition from Collisional to Collisionless Regimes in Interpenetrating Plasma Flows on the National Ignition Facility. Physical Review Letters, 118 (18), 10.1103/PhysRevLett.118.185003
DOI: doi:10.1103/PhysRevLett.118.185003
ISSN: 0031-9007
EISSN: 1079-7114
Type of Material: Journal Article
Journal/Proceeding Title: Physical Review Letters
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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