Proton acceleration in an overdense hydrogen plasma by intense CO2 laser pulses with nonlinear propagation effects in the underdense pre-plasma
Abstract
We report on proton acceleration from intense CO2 laser-irradiated hydrogen plasmas at near-critical densities, with the density gradient steepened by Nd:YAG laser ablation-driven hydrodynamic shocks. While the experimental results, such as the quasi-monoenergetic proton spectra and their scaling with respect to the laser energy, are generally in agreement with the simulations, certain laser shots produced significantly higher proton energies than anticipated during the experiment. The increased proton energy may be linked to nonlinear propagation effects in the steepened plasma density ramp before the critical surface, including relativistic self-focusing and, for the case of temporally-structured laser pulses observed in the experiment, focusing of the trailing pulse through the plasma channel formed by the leading pulse 25 ps ahead. The occurrence of channel focusing in the underdense hydrogen plasma is supported by a subsequent pump-probe experiment with a dark-field imaging technique, where the formation of ion channels was observed after the passage of an intense CO2 laser pulse.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 01, 2023
- Source ID
- 10.1063/5.0142239
Entities
People
- Antonio Ting
- Bahman Hafizi
- D. Gordon
- Emma-jane Ditter
- George Hicks
- Igor Pogorelsky
- Luke A. Johnson
- M. Babzien
- Michael Helle
- Mikhail N Polyanskiy
- Nicholas Peter Dover
- Oliver C. Ettlinger
- Yu-hsin Chen
- Zulfikar Najmudin
Organizations
- Brookhaven National Laboratory
- Imperial College London
- MITRE Corporation
- United States Department of Energy
- United States Naval Research Laboratory
- University of Maryland