Strong electromagnetic pulses (EMPs) are generated from intense laser interactions with solid-density targets and can be guided by the target geometry, specifically through conductive connections to the ground. We present an experimental characterization by time- and spatial-resolved proton deflectometry of guided electromagnetic discharge pulses along wires including a coil, driven by 0.5 ps, 50 J, 1019 W/cm2 laser pulses. Proton-deflectometry allows us to time-resolve first the EMP due to the laser-driven target charging and then the return EMP from the ground through the conductive target stalk. Both EMPs have a typical duration of tens of ps and correspond to currents in the kA-range with electric-field amplitudes of multiple GV/m. The sub-mm coil in the target rod creates lensing effects on probing protons due to both magnetic- and electric-field contributions. This way, protons of the 10 MeV-energy range are focused over cm-scale distances. Experimental results are supported by analytical modeling and high-resolution numerical particle-in-cell simulations, unraveling the likely presence of a surface plasma, in which parameters define the discharge pulse dispersion in the non-linear propagation regime.
Bibliographical noteFunding Information:
We want to thank our funding projects POPRA (Project No. 29910), IdEx U-BOR, and CRA-ARIEL. P.K. acknowledges support from the Project Ministry of Science and Higher Education of the Russian Federation via No. FSWU-2020–0035. This work was granted access to the HPC resources of CINES under Allocation Nos. 2016–056129 and 2017–056129 made by GENCI (Grand Equipement National de Calcul Intensif). This work has been carried out within the frameworks the Investments for the Future Program IdEx Université de Bordeaux/GPR LIGHT and of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement Nos. 633053 and 101052200—EUROfusion). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. This work has received funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 871124 Laserlab-Europe.
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