We report the generation of a 6 pC, 23 MeV electron bunch with the energy spread ± 3.5% by using 2 TW, 80 fs high contrast laser pulses interacting with helium gas targets. Within the optimized experimental condition, we obtained quasi-monoenergetic electron beam with an ultra-small normalized divergence angle of 92 mrad, which is at least 5 times smaller than the previous LPA-produced bunches. We suggest the significant decrease of the normalized divergence angles is due to smooth transfer from SM-LWFA to LWFA. Since the beam size in LPA is typically small, this observation may explore a simple way to generate ultralow normalized emittance electron bunches by using small-power but high-repetition-rate laser facilities.

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Abstract. Laser plasmas are capable of creating unique physical conditions with extreme high energy density, which are not only closely relevant to inertial fusion energy studies, but also to laboratory simulation of some astrophysical processes. In this paper, we highlight some recent progress made by our research teams. The first part is about directional hot electron beam generation and transport for fast ignition of inertial confinement fusion, as well as a new scheme of fast ignition by use of a strong external DC magnetic field. The second part concerns laboratory modeling of some astrophysical phenomena, including 1) studies of the topological structure of magnetic reconnection/annihilation that relates closely to geomagnetic substorms, loop-top X-ray source and mass ejection in solar flares, and 2) magnetic field generation and evolution in collisionless shock formation.

A method is proposed to control the transverse motion and X-ray emission of an electron beam in a laser driven wakefield by tuning the laser spatial chirp. The dispersion of a transversely chirped laser pulse and the transverse nonuniform refractive index of the plasma channel result in transverse laser centroid oscillations, which leads to periodic transverse oscillations of the laser-driven wake. Electrons accelerated inside the wake also undergo transverse oscillations making wiggler like motion. Both the oscillation period and amplitude can be controlled by tuning the laser chirp, the pulse duration or the plasma channel width. As a result, the far field spectral distributions of the X-ray emission can be flexibly manipulated.