Generating beams of electrons, ions, and neutrons with intense lasers

Intense lasers enable a range of schemes for generating high-energy particle beams in university-scale laboratories. I will describe two on-going experimental campaigns on this topic.

In direct laser acceleration (DLA), the leading edge of the laser pulse ionizes the target material, forming a positively charged plasma channel that traps and accelerates electrons. DLA offers exceptional conversion efficiency, often exceeding 20%, making it highly suitable for driving secondary radiation sources. This talk reviews recent advances aimed at pushing the efficiency and applicability of DLA for X-ray and neutron generation. I will present experimental and numerical studies showing how DLA performance can be enhanced by tailoring the target’s atomic number to sustain electron injection, and by employing flying-focus pulses to stabilize the plasma channel and extend the acceleration length.

Building on these developments, I will demonstrate how high accumulated neutron yields were achieved via bremsstrahlung from MeV electron beams in high-repetition-rate laser shots.

I will also present a study of proton acceleration by intense laser irradiation of micrometric bar targets, whose dimensions are transversely immersed in the laser focal volume and longitudinally smaller than half its wavelength. Using only 120 mJ of laser energy, we recorded proton energies in excess of 6 MeV, exceeding those reported with irradiation of foil targets by a factor of 3. This technique opens up the possibility of laser ion acceleration in multiple stages, allowing manipulation of the accelerated ion spectrum by optical means.