Measurement of strong electromagnetic pulses generated from solid targets at sub-ns kJ-class PALS laser facility

Abstract

Measurements had been performed of strong electromagnetic pulses (EMPs) generated as a result of laser–target interaction at the sub-ns kJ-class Prague Asterix Laser System facility. Two conductive Prodyn FD5C D-dot pencil probes were used. Measurements were performed inside the experimental chamber and outside the chamber in a large chamber window 40 cm in diameter in a setup that guaranteed 6 GHz bandwidth. A very good signal-to-noise ratio (17:1) was obtained after some steps were taken to ensure proper EMP shielding of the data collection setup. The EMP signal in the time domain was found to have the form of a sharp initial spike followed by gradually decaying oscillations interspersed with some secondary spikes. The values of the vertical component of the electric field strength were estimated. The highest value recorded in this experiment was 620 − 180 + 260 kV m−1 at a distance of 40 cm from the target. It was observed that plastic targets—particularly the 100s of µm thick plastic foils—tend to generate stronger EMP fields than Cu and Au targets. A time-frequency analysis was performed for a typical shot, clearly showing some spectral features that appear only sometime after the start of the signal and hence indicate EMP generation from secondary sources. Electrons ejected from the target were recorded with the energies exceeding 1.5 MeV, which indicates that highly energetic processes are triggered as a result of the laser–target interaction.

High-Sensitivity Thomson Spectrometry in Experiments of Laser-Driven Low-Rate NeutronLess Fusion Reactions

“…[12] where very similar laser-plasma interaction conditions were exploited but the TS device was place outside the interaction chamber where the EMPs have signifcantly less intensity. Tis indicates that the shielding against this type of radiation provided good protection to our device despite the presence of EMP felds presumably in the order of magnitude of above 0.5 MV/m, as measured at the PALS facility [37]. Our setup allowed to cover a large solid angle, more than one order of magnitude higher with respect to previous other setups where the TS was placed 1.5-2 m far from target.…”

“…[31] for further details) effectively protected the region of the IP where the ions were revealed. Our TS also proved to have remarkable robustness to signifcant EMP felds (typically, at the PALS facility, in the order of a fraction of MV/m at ∼1 m distance the target [24,37]). Te traces do not feature the typical oscillations that are caused by the presence of EMPs when no special precautions are taken.…”

Electromagnetic pulses produced by a picosecond laser interacting with solid targets

“…[4] Raczka et al indicated that an EMP induced by laser (290 ± 20 ps, 590 ± 30 J) interaction with plas-tic foils reached around 620 kV/m at Prague Asterix Laser System facility. [5] Bradford et al revealed the relationship between EMP energy and the total number of escaping electrons with ps laser pulse duration. [6] Our recent experimental results also confirmed that a ps pulse shooting solid targets caused more intense EMPs compared to ns and fs pulses.…”