Guided electromagnetic discharge pulses driven by short intense laser pulses: Characterization and modeling
M. Ehret, M. Bailly-Grandvaux, Ph. Korneev, Jon Imanol Apiñaniz, C. Brabetz, A. Morace, P. Bradford, E. d’Humières, G. Schaumann, V. Bagnoud, S. Malko, Ksenia Matveevskii, M. Roth, L. Volpe, N. C. Woolsey, J. J. Santos
Abstract
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.