Diagnosing laser-driven,shock-heated foam target with Al absorption spectroscopy on OMEGA EP |
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Authors: | H Sawada T Yabuuchi SP Regan K Anderson MS Wei R Betti J Hund MH Key AJ Mackinnon HS McLean RR Paguio PK Patel KM Saito RB Stephens SC Wilks FN Beg |
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Affiliation: | 1. Center for Energy Research, University of California, San Diego, La Jolla, CA 92093, USA;2. Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623, USA;3. General Atomics, San Diego, CA 92186, USA;4. Lawrence Livermore National Laboratory, Livermore, CA 94551, USA |
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Abstract: | Results on diagnoses of laser-driven, shock-heated foam plasma with time-resolved Al 1s-2p absorption spectroscopy are reported. Experiments were carried out to produce a platform for the study of relativistic electron transport. In cone-guided Fast Ignition (FI), relativistic electrons generated by a high-intensity, short-pulse igniter beam must be transported through a cone tip to an imploded core. Transport of the energetic electrons could be significantly affected by the temperature-dependent resistivity of background plasmas. The experiment was conducted using four UV beams of the OMEGA EP laser at the Laboratory For Laser Energetics. One UV beam (1.2 kJ, 3.5 ns square) was used to launch a shock wave into a foam package target, consisting of 200 mg/cm3 CH foam with aluminum dopant and a solid plastic container surrounding the foam layer. The other three UV beams with the total energy of 3.2 kJ in 2.5 ns pulse duration were tightly focused onto a Sm dot target to produce a point X-ray source in the energy range of 1.4–1.6 keV. The quasi-continuous X ray signal was transmitted through the shock-heated Al-doped, foam layer and recorded with an X-ray streak camera. The measured 1s-2p Al absorption features were analyzed using an atomic physics code FLYCHK. Electron temperature of 40 eV inferred from the spectral analysis is consistent with 2-D DRACO Radiation-hydrodynamic simulations. |
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