Monoenergetic High-energy Ion Source via Femtosecond Laser Incident Parallel to a Microplate

TL;DR

This study demonstrates through 3D simulations that femtosecond lasers can produce stable, high-energy, monoenergetic proton beams by parallel irradiation of a microplate, surpassing traditional acceleration methods.

Contribution

It introduces a novel laser-plate configuration that efficiently generates high-energy, monoenergetic protons with low energy spread using readily available femtosecond laser systems.

Findings

Proton energies reach hundreds of MeV with ~1% energy spread.

The method produces higher proton energies than conventional NTSA and RPA.

A stable, monoenergetic proton beam is achieved via electron-driven electrostatic fields.

Abstract

Using fully three-dimensional particle-in-cell simulations, we show that readily available femtosecond laser systems can stably generate proton beams with hundred MeV energy and low spread at $\sim1\%$ level by parallel irradiation of a tens of micrometers long plasma plate. As the laser pulse sweeps along the plate, it drags out a huge charge ($\sim$100 nC) of collimated energetic electrons and accelerates them along the plate surface to superponderomotive energies. When this dense electron current arrives at the rear end of the plate, it induces a strong electrostatic field. Due to the excessive space charge of electrons, the longitudinal field becomes bunching while the transverse field is focusing. Together, this leads to a highly monoenergetic energy spectrum and much higher proton energy as compared to simulation results from typical target normal sheath acceleration and radiation pressure acceleration at the same laser parameters.