Abstract
We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation.
Highlights
We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime
EMPs have been previously characterized with conductive probes[3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], but only a few works address the absolute measurements of the associated electric fields, which are accomplished by D-dot and B-dot probes[25,26]
We have described the first direct electric-field measurements of EMPs generated by laser-target interaction in ICF regime, performed by dielectric EO-probes directly viewing the plasma
Summary
Thermal ion emission from plasma was measured by Time-of-Flight (TOF) detection with a set of faraday-cups; a particle contribution with Eion/A ~ 1 keV (A = atomic number) is shown in Fig. 3a at φ = 53° from the target normal. The simulated configuration is very simple, and does not allow to get a remarkable fitting with experimental data; calculations indicate that the low-frequency components of measured spectra are compatible with fields generated by particle flows. This might confirm that the classical high-frequency components, showed in the spectrum of the SWB-antenna signal (see Fig. 5), are likely cavity modes excited within the experimental chamber[4,15,16]. E2X′ (~Er) is not affected by this (Fig. 7b)
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