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Title: Plasma dynamics near critical density inferred from direct measurements of laser hole boring

Here, we use multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of CO2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. We present a heuristic theory that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. Furthermore, the measured values of vHB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Univ. of California, Los Angeles, CA (United States). Electrical Engineering Dept.
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-737704
Journal ID: ISSN 2470-0045; PLEEE8
Grant/Contract Number:
AC52-07NA27344; NA0002950; SC0010064
Type:
Publisher's Accepted Manuscript
Journal Name:
Physical Review E
Additional Journal Information:
Journal Volume: 93; Journal Issue: 6; Journal ID: ISSN 2470-0045
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 70 PLASMA PHYSICS AND FUSION; 42 ENGINEERING; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1259336
Alternate Identifier(s):
OSTI ID: 1389949