Analysis of electromagnetic pulses generated from ultrashort laser irradiation of solid targets at CLAPA

Abstract

Electromagnetic pulses (EMPs) produced by the interaction of a TW femtosecond laser with solid targets at the Compact Laser Plasma Accelerator (CLAPA) are measured and interpreted. The statistical results confirm that the intensities of the EMPs are closely related to both target material and thickness. The signal of the titanium target is more abundant than that of the copper target with the same thickness, and the intensity of EMP is positively correlated with the target thickness for aluminium foil. With the boosted EMP radiations, the energy of accelerated protons is also simultaneously enhanced. In addition, EMPs emitted from the front of the target exceed those from the rear, which are also pertinent to the specific target position. The resonant waveforms in the target chamber are analyzed using the fast Fourier transform, and the local resonance and the attenuation lead to changes of the frequency spectra of EMPs with variation of detecting positions, which is well supported by the modeling results. The findings are beneficial to gaining insight into the mechanism of EMP propagation in a typical target chamber and providing more information for EMP shielding design.