Observation of impurity free monoenergetic proton beams from the interaction of a CO2 laser with a gaseous target

Abstract

A monoenergetic proton beam is observed from the interaction of a short-pulse infrared (λ = 10.6 μm) laser at intensity I = 6 × 1015 W cm−2 with a gas jet target. The proton beam is found to have narrow energy spread (∼ 4% ), high spectral brightness (∼ 1012 protons/MeV/sr), low normalized emittance (εn ≈ 8 nm rad), and high contrast (> 200 × over noise). The narrow energy spread and low levels of impurity makes this method an interesting route for high-repetition rate high quality proton beam production.