Background pressure effects on MeV protons accelerated via relativistically intense laser-plasma interactions
Abstract
We present how chamber background pressure affects energetic proton acceleration from an ultra-intense laser incident on a thin liquid target. A high-repetition-rate (100 Hz), 3.5 mJ laser with peak intensity of $$8 \times 10^{18}\,\text {Wcm}^{-2}$$ 8 × 10 18 Wcm - 2 impinged on a 450 nm sheet of flowing liquid ethylene glycol. For these parameters, we experimentally demonstrate a threshold in laser-to-proton conversion efficiency at background pressures $$ 8 Torr , wherein the overall energy in ions $$>1\,\text {MeV}$$ > 1 MeV increases by an order of magnitude. Proton acceleration becomes increasingly efficient at lower background pressures and laser-to-proton conversion efficiency approaches a constant as the vacuum pressure decreases. We present two-dimensional particle-in-cell simulations and a charge neutralization model to support our experimental findings. Our experiment demonstrates that high vacuum is not required for energetic ion acceleration, which relaxes target debris requirements and facilitates applications of high-repetition rate laser-based proton accelerators.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 26, 2020
- Source ID
- 10.1038/s41598-020-75061-1
Entities
People
- Christopher Orban
- Enam Chowdhury
- Gregory Ngirmang
- John Morrison
- Joseph Snyder
- Kevin George
- Kyle Frische
- Manh Le
- Scott Feister
- W. M. Roquemore
Organizations
- Air Force Office of Scientific Research