Sub-millimeter-scale, 100-MeV-class quasi-monoenergetic laser plasma accelerator based on all-optical control of dark current in the blowout regime

Abstract

It is demonstrated that by negatively chirping the frequency of a 20-fs, 15-TW driving laser pulse with an ultrabroad bandwidth (corresponding to a sub-2-cycle transform-limited duration) it is possible to prevent early compression of the pulse into an optical shock, thus reducing expansion of the accelerating plasma bucket (electron density "bubble") and delaying dephasing of self-injected and accelerated electrons. These features help suppress unwanted continuous selfinjection (dark current) in the blowout regime, making possible to use the entire dephasing length to generate lowbackground, quasi-monoenergetic 200-MeV-scale electron beams from sub-mm-length dense plasmas (n e0 =1.3×10 19 cm −3 ).