Target Charging, Strong Electromagnetic Pulse Emission and Proton Acceleration from Thin Foils at 10 TW IPPLM Femtosecond Laser Facility

It is well known that the laser-target interaction at high power and high laser intensity may result in the emission of strong electromagnetic pulses with frequencies in the range from tens of MHz to a few GHz and the duration of hundreds of nanoseconds. It was recently pointed out that the electric polarization of the target and the resulting neutralization current play an important role in the electromagnetic pulses emission. The target charge and the neutralization current generated with laser pulses of 30 fs to several ps duration were studied in detail at the Eclipse laser facility at CELIA, Bordeaux, with the laser pulse energy at the level of up to 100 mJ on target. In this contribution we report on the measurements of the target charge and the electromagnetic pulses performed at the 10 TW fs laser facility in IPPLM, Warsaw, for the laser pulse energies reaching 400 mJ on target and the laser pulse duration in the range of 50 fs to 400 fs. Due to higher laser pulse energy, the effect of proton acceleration off the rear side of the thin foil targets could be easily observed. This is an important bonus since the mechanism of target normal sheath acceleration of protons which prevails in these laser conditions is closely related to the mechanism of charge ejection from the target, thus providing an additional constraint on any attempts at modeling of the target charge. The collected data is confronted with simplified models of charge ejection and target normal sheath acceleration of protons and qualitative agreement is found.