Laser structured micro-targets generate MeV electron temperature at $4 \times 10^{16}$ W/cm$^2$

TL;DR

This paper introduces a novel laser-target structuring technique that produces relativistic electron temperatures at significantly lower laser intensities than traditional methods, enabling compact electron sources with high repetition rates.

Contribution

The authors develop a dynamic microdroplet structuring method that achieves relativistic electron temperatures at 4×10^{16} W/cm^{2}, much lower than the standard threshold, using ultrashort laser pulses.

Findings

Achieved 200 keV to 1 MeV electron temperatures at 4×10^{16} W/cm^{2}.

Demonstrated kHz shot repeatability with directed electron beams.

Produced MeV electron energies suitable for scientific applications.

Abstract

Relativistic temperature electrons higher than 0.5 MeV are generated typically with laser intensities of about 10$^{18}$ W/cm$^{2}$. Their generation with high repetition rate lasers that operate at non-relativistic intensities ($\simeq$10$^{16}$ W/cm$^{2}$) is cardinal for the realization of compact, ultra-short, bench-top electron sources. New strategies, capable of exploiting different aspects of laser-plasma interaction, are necessary for reducing the required intensity. We report here, a novel technique of dynamic target structuring of microdroplets, capable of generating 200 keV and 1 MeV electron temperatures at 1/100th of the intensity required by ponderomotive scaling($10^{18}$ W/cm$^2$) to generate relativistic electron temperature. Combining the concepts of pre-plasma tailoring, optimized scale length and micro-optics, this method achieves two-plasmon decay boosted electron acceleration with "non-ideal" ultrashort (25 fs) pulses at $4\times10^{16}$ W/cm$^2$, only. With shot repeatability at kHz, this precise in-situ targetry produces directed, imaging quality beam-like electron emission up to 6 MeV with milli-joule class lasers, that can be transformational for time-resolved, microscopic studies in all fields of science.