Charge equilibration of Laser-accelerated Carbon Ions in Foam Target

TL;DR

This study experimentally investigates charge equilibration of laser-accelerated carbon ions in foam targets, revealing density effects on ionization and providing insights for high energy density physics and related applications.

Contribution

It introduces the first experimental measurement of charge states in foam targets at various energies, highlighting the role of target density in ionization processes.

Findings

Charge states are underestimated by gas-phase theoretical models.

Foam targets increase ionization probability and reduce electron capture.

Double electron processes have minimal impact on average charge states.

Abstract

The charge equilibration of laser-accelerated carbon ion beams in 2 mg/cm3 foam target was investigated experimentally. The ions were generated through target normal sheath acceleration mechanism in laser-foil interaction scheme. This allows to get the equilibrium charge state in wide energy range near Bragg peak within a single shot. By using foam, the charge equilibration measurement in density regime between gas and solid state was firstly reached out experimentally. It was found that the theoretical predictions with tabulated cross section data for gas target greatly underestimated the charge states. The experimental data are in close agreement with both semi-empirical formula as well as rate equation predictions based on ion-solid interactions. The important role of target density effects that increase the ionization probability and decrease the electron capture probability through frequent multi-collisions in foam are demonstrated. The double electron processes are shown to have little influence on the average charge states. The findings are essential for high energy density physics research where the foams are widely used, and have impacts on a broad range of applications in medical, biological and material fields. The method also provides a new approach to investigate the interaction mechanism of swift heavy ions in matter by taking advantage of the laser-accelerated short-pulse wide-energy range ions.