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

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) counterstreaming 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 counterstreaming 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. Here, the observed plasma heating and enhanced neutron production is consistent with the initial stages of collisionless shock formation, mediated by the Weibel filamentation instability.
Authors:
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Stanford Univ., Stanford, CA (United States). SLAC National Accelerator Lab.
  3. Univ. of Rochester, Rochester, NY (United States)
  4. Kyushu Univ., Fukuoka (Japan)
  5. Osaka Univ., Osaka (Japan)
  6. Univ. of Michigan, Ann Arbor, MI (United States)
  7. Univ. of Oxford, Oxford (United Kingdom)
  8. Ecole Polytechnique, Palaiseau (France)
  9. Princeton Univ., Princeton, NJ (United States)
  10. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  11. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-700999
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
AC52-07NA27344; 15-ERD-065
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 118; Journal Issue: 18; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 70 PLASMA PHYSICS AND FUSION
OSTI Identifier:
1366948
Alternate Identifier(s):
OSTI ID: 1355971