Probing ultrafast magnetic-field generation by current filamentation instability in femtosecond relativistic laser-matter interactions

Raj, G. and Kononenko, O. and Gilljohann, M. F. and Doche, A. and Davoine, X. and Caizergues, C. and Chang, Y.-Y. and Couperus Cabadağ, J. P. and Debus, A. and Ding, H. and Förster, M. and Goddet, J.-P. and Heinemann, T. and Kluge, T. and Kurz, T. and Pausch, R. and Rousseau, P. and San Miguel Claveria, P. and Schöbel, S. and Siciak, A. and Steiniger, K. and Tafzi, A. and Yu, S. and Hidding, B. and Martinez de la Ossa, A. and Irman, A. and Karsch, S. and Döpp, A. and Schramm, U. and Gremillet, L. and Corde, S. (2020) Probing ultrafast magnetic-field generation by current filamentation instability in femtosecond relativistic laser-matter interactions. Physical Review Research, 2 (2). 023123. ISSN 2643-1564

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    Abstract

    The current filamentation instability is a key phenomenon underpinning various processes in astrophysics, laboratory laser-plasma, and beam-plasma experiments. Here we show that the ultrafast dynamics of this instability can be explored in the context of relativistic laser-solid interactions through deflectometry by low-emittance, highly relativistic electron bunches from a laser wakefield accelerator. We present experimental measurements of the femtosecond timescale generation of strong magnetic-field fluctuations, with a measured line-integrated B field of 2.70 ± 0.39 kT μm. Three-dimensional, fully relativistic particle-in-cell simulations demonstrate that such fluctuations originate from the current filamentation instability arising at submicron scales around the irradiated target surface, and that they grow to amplitudes strong enough to broaden the angular distribution of the probe electron bunch a few tens of femtoseconds after the laser pulse maximum. Our results open a branch of physics experiments investigating the femtosecond dynamics of laser-driven plasma instabilities by means of synchronized, wakefield-accelerated electron beams.