Laser-plasma accelerator group

Abstract:

<jats:p>The plasma photocathode has previously been proposed as a source of ultrahigh-brightness electron bunches within plasma accelerators. Here, the scheme is extended by using a radially-polarized ionizing laser pulse to generate high-charge, high-brightness electron bunches with transverse emittance. Efficient start-to-end modeling of the scheme, from ionization and trapping until drive bunch depletion, enables a multiobjective Bayesian optimization routine to be performed to understand the performance of the radially-polarized plasma photocathode, quantify the stability of the scheme, and explore the fundamental relation between the witness bunch charge and its emittance. Comparison of plasma photocathodes driven by radially- and linearly-polarized laser pulses shows that the former yields higher-brightness electron bunches when operating in the optimally-loaded regime.</jats:p>

Abstract:

Laser-plasma accelerators present a promising alternative to conventional accelerators. To fully exploit the extreme amplitudes of the plasma fields and produce high-quality beams, precise control over electron injection into the accelerating structure is required, along with effective laser pulse guiding to extend the acceleration length. Recent studies have demonstrated efficient guiding and acceleration using hydrodynamic optically field-ionized plasma channels. This guiding technique has also been combined with controlled electron injection to produce high-quality electron beams at the GeV level using a 50 TW laser. The present work extends these results to higher laser power, demonstrating the generation of quasimonoenergetic electron beams with peak energies exceeding 2 GeV, for a PW-class laser.

Abstract:

Betatron radiation is produced in laser plasma accelerators when the electrons are accelerated and simultaneously wiggle across the propagation axis [Rousse et al., Phys. Rev. Lett. 93, 135005 (2004)]. The mechanisms of electron acceleration and x-ray radiation production follow different scaling laws [Corde et al., Rev. Mod. Phys. 85, 1–48 (2013)], and the brightest x-ray radiation is often produced for an electron beam with a lower quality in terms of energy and divergence. Here, we report a laser-driven betatron x-ray source where the plasma density profile is tailored in order to separate the acceleration and wiggler stages, which allows for the independent optimizations of acceleration and x-ray production. We demonstrate this concept experimentally and show that the betatron photon energy can be controlled by adjusting the length of the plasma wiggler. This scheme offers a path to overcome the limitations of conventional betatron sources, enabling the production of bright, stable, energetic, and collimated x-ray beams.