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.

Electromagnetic pulses produced by a picosecond laser interacting with solid targets

“…2(b), which can be attributed to various possible sources of EMPs and the effects of some internal real arrangements in the target chamber. [8,18] The obtained frequencies are similar to some reported results. At the XG-III laser facility, resonant frequencies (TE111, TM010, TE011) were calculated by simplifying the chamber based on the ideal cylindrical target chamber models, where three typical resonant frequencies of 140.4 MHz, 104.9 MHz and 210 MHz were obtained.…”

“…[17] Yilin et al found that the EMP signal induced by a fs laser was lifted with the increase of the aluminum target thickness from 1.8 µm to 70 µm, and the target material also affected the EMP amplitude. [18] Therefore, there are discrepancies that exist in the effects of target thickness.…”

Spatial and temporal evolution of electromagnetic pulses from solid target irradiated with multi-hundred-terawatt laser pulse inside target chamber

“…The echo oscillation of electromagnetic waves inside the target chamber is responsible for the enhancement of EMPs. When EMPs reach the target chamber wall, they are partially attenuated due to absorption by the wall, while the remain-ing EMPs are reflected [51,52]. The superposition of incident electromagnetic waves and reflected electromagnetic waves contributes to more intense EMPs, accounting for the stronger EMP closer to the target chamber wall.…”