Anomalous material-dependent transport of focused, laser-driven proton beams.

Autor: Kim J; Center for Energy Research, University of California, San Diego, La Jolla CA, 92093-0417, USA., McGuffey C; Center for Energy Research, University of California, San Diego, La Jolla CA, 92093-0417, USA., Gautier DC; Los Alamos National Laboratory, Los Alamos, NM, 87545, USA., Link A; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA., Kemp GE; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA., Giraldez EM; General Atomics, San Diego, CA, 92186-5608, USA., Wei MS; General Atomics, San Diego, CA, 92186-5608, USA., Stephens RB; General Atomics, San Diego, CA, 92186-5608, USA., Kerr S; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA.; University of Alberta, Edmonton, Alberta, T6G 2V4, Canada., Poole PL; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA.; Physics Department, The Ohio State University, Columbus, OH, 43210, USA., Madden R; Center for Energy Research, University of California, San Diego, La Jolla CA, 92093-0417, USA., Qiao B; Center for Energy Research, University of California, San Diego, La Jolla CA, 92093-0417, USA., Foord ME; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA., Ping Y; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA., McLean HS; Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA., Fernández JC; Los Alamos National Laboratory, Los Alamos, NM, 87545, USA., Beg FN; Center for Energy Research, University of California, San Diego, La Jolla CA, 92093-0417, USA. fbeg@ucsd.edu.
Jazyk: angličtina
Zdroj: Scientific reports [Sci Rep] 2018 Dec 03; Vol. 8 (1), pp. 17538. Date of Electronic Publication: 2018 Dec 03.
DOI: 10.1038/s41598-018-36106-8
Abstrakt: Intense lasers can accelerate protons in sufficient numbers and energy that the resulting beam can heat materials to exotic warm (10 s of eV temperature) states. Here we show with experimental data that a laser-driven proton beam focused onto a target heated it in a localized spot with size strongly dependent upon material and as small as 35 μm radius. Simulations indicate that cold stopping power values cannot model the intense proton beam transport in solid targets well enough to match the large differences observed. In the experiment a 74 J, 670 fs laser drove a focusing proton beam that transported through different thicknesses of solid Mylar, Al, Cu or Au, eventually heating a rear, thin, Au witness layer. The XUV emission seen from the rear of the Au indicated a clear dependence of proton beam transport upon atomic number, Z, of the transport layer: a larger and brighter emission spot was measured after proton transport through the lower Z foils even with equal mass density for supposed equivalent proton stopping range. Beam transport dynamics pertaining to the observed heated spot were investigated numerically with a particle-in-cell (PIC) code. In simulations protons moving through an Al transport layer result in higher Au temperature responsible for higher Au radiant emittance compared to a Cu transport case. The inferred finding that proton stopping varies with temperature in different materials, considerably changing the beam heating profile, can guide applications seeking to controllably heat targets with intense proton beams.
Databáze: MEDLINE
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