Electron acceleration at oblique angles via stimulated Raman scattering at laser irradiance >1016 W cm–2μm2
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- Univ. of California, San Diego, CA (United States)
- Univ. of California, Los Angeles, CA (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Univ. of Warwick, Coventry (United Kingdom)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Texas, Austin, TX (United States)
- Univ. of Rochester, NY (United States). Lab. for Laser Energetics
- General Atomics, San Diego, CA (United States)
The generation of hot, directional electrons via laser-driven stimulated Raman scattering (SRS) is a topic of great importance in inertial confinement fusion (ICF) schemes. Little recent research has been dedicated to this process at high laser intensity, in which back, side, and forward scatter simultaneously occur in high energy density plasmas, of relevance to, for example, shock ignition ICF. In this paper, we present an experimental and particle-in-cell (PIC) investigation of hot electron production from SRS in the forward and near-forward directions from a single speckle laser of wavelength λ0 = 1.053μm, peak laser intensities in the range I0 = 0.2–1.0×1017 Wcm–2 and target electron densities between ne = 0.3–1.6% nc, where nc is the plasma critical density. As the intensity and density are increased, the hot electron spectrum changes from a sharp cutoff to an extended spectrum with a slope temperature T = 34 ± 1 keV and maximum measured energy of 350 keV experimentally. Multidimensional PIC simulations indicate that the high energy electrons are primarily generated from SRS-driven electron plasma wave phase fronts with k vectors angled ~50° with respect to the laser axis. These results are consistent with analytical arguments that the spatial gain is maximized at an angle which balances the tendency for the growth rate to be larger for larger scattered light wave angles until the kinetic damping of the plasma wave becomes important. The efficiency of generated high energy electrons drops significantly with a reduction in either laser intensity or target electron density, which is a result of the rapid drop in growth rate of Raman scattering at angles in the forward direction.
- Research Organization:
- Univ. of California, San Diego, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Grant/Contract Number:
- NA0003842; NA0003943; SC0019010; AC02-05CH11231; 57789; 536203; B632670
- OSTI ID:
- 1784753
- Journal Information:
- Physical Review E, Vol. 103, Issue 3; ISSN 2470-0045
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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