Reduce proton energy spread by target ablation

TL;DR

This paper demonstrates that strong target ablation during laser aluminum foil interaction can produce monoenergetic protons and reduce energy spread, differing from classic TNSA theory, especially when pre-pulse vaporizes the target.

Contribution

It introduces a novel method of reducing proton energy spread via target ablation and electron beam dynamics, contrasting with traditional TNSA mechanisms.

Findings

Monoenergetic protons achieved along laser direction.

Target ablation influences ion acceleration mechanisms.

Electron beam-driven sheath fields reduce energy spread.

Abstract

It's shown that, with strong target ablation monoenergetic protons along the laser direction is available during the laser aluminum foil interaction, which is different from the classic TNSA theory. When the laser pre-pulse is too strong that the whole target is vaporized, the energetic electrons generated in the gas preplasma will play an important role for the ion acceleration because the sheath field will not be available. These electrons beam, which is highly directional, will setup triangle envelope acceleration field along the laser direction at the target rear, reducing the ion energy spread.