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The interaction of a 3×1019 W/cm2 laser pulse with a metallic wire has been investigated using proton radiography. The pulse is observed to drive the propagation of a highly transient field along the wire at the speed of light. Within a temporal window of 20 ps, the current driven by this field rises to its peak magnitude ∼104 A before decaying to below measurable levels. Supported by particle-in-cell simulation results and simple theoretical reasoning, the transient field measured is interpreted as a charge-neutralizing disturbance propagated away from the interaction region as a result of the permanent loss of a small fraction of the laser-accelerated hot electron population to vacuum.
Quinn, K., Wilson, P. A., Cecchetti, C. A., Ramakrishna, B., Romagnani, L., Sarri, G., Lancia, L., Fuchs, J., Gallegos, P., Carroll, D. C., Quinn, M. N., Yuan, X. H., & McKenna, P. (2009). Laser-driven ultrafast field propagation on solid surfaces. Physical Review Letters, 102(19), 194801-1-194801-4. https://doi.org/10.1103/PhysRevLett.102.194801