Enhanced laser-driven proton acceleration from a relativistically transparent transversely nano-striped target

• Published in: Plasma physics and controlled fusion 2015-11, Vol.57 (11), p.115009
• Main Authors: Wang, Jingwei, Murakami, Masakatsu, Xu, Han, Ju, Jingjing, Yu, Wei
• Format: Article
• Language: English
• Subjects: Acceleration; Density; Gold; Hydrogen; Laser beams; laser plasma interaction; laser-driven proton acceleration; Lasers; Lorentz factor; Nanostructure; relativistic transparency
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/0741-3335/57/11/115009

Enhanced laser-driven proton acceleration occurs when an intense laser interacts with a transversely nano-striped target consisted of alternate gold and hydrogen stripes. The density of the laser-irradiated hydrogen stripes initially decreases to less than the critical density, enabling the laser field to penetrate into the hydrogen stripes and heat the electrons in the still-opaque gold stripes. The resulting increase in the electron Lorentz factor and the expansion of all the electrons ultimately make the entire target relativistically transparent to the latter part of the laser beam. Large numbers of hot electrons are expelled from the target because the laser volumetrically interacts with the whole target. A fairly high electrostatic field is then induced on the rear side of the target to accelerate the protons. When compared with double-layer or single-layer targets, the proton acceleration is much more efficient in the relativistically transparent nano-striped target presented here. Two spatial and three velocity dimensions (2D3V) particle-in-cell simulations show that with an W cm−2 laser, a proton beam with a maximum energy of approximately 190 MeV can be generated.