We present the first experimental evidence supported by simulations of kinetic effects launched in the interpenetration layer between the laser-driven hohlraum plasma bubbles and the corona plasma of the compressed pellet at the Shenguang-III prototype laser facility. Solid plastic capsules were coated with carbon-deuterium layers; as the implosion neutron yield is quenched, DD fusion yield from the corona plasma provides a direct measure of the kinetic effects inside the hohlraum. An anomalous large energy spread of the DD neutron signal (∼282  keV) and anomalous scaling of the neutron yield with the thickness of the carbon-deuterium layers cannot be explained by the hydrodynamic mechanisms. Instead, these results can be attributed to kinetic shocks that arise in the hohlraum-wall-ablator interpenetration region, which result in efficient acceleration of the deuterons (∼28.8  J, 0.45% of the total input laser energy). These studies provide novel insight into the interactions and dynamics of a vacuum hohlraum and near-vacuum hohlraum.

Controlling beam loading is essential to produce large-charge high-quality electron beams in laser wakefield acceleration. The bunch shape in the longitudinal direction is a key factor to optimize beam loading. However, how to generate an electron beam with an appropriate shape is always a difficult problem to solve. In the present paper, indirect manipulation on the bunch shape is realized by tuning the laser profile. This is because that the bunch shape relies on the initial transverse position of electrons, which can be controlled by the laser profile in the optical injection scheme. Based on this indirect manipulation method, we find that by reducing the focal spot size of the injection pulse and thus effectively inhibiting off-axis electron injection, the electron beam shape gradually changes from down-ramp to flat-top, which is more favorable for optimizing beam loading. Consequently, we use a cigar-like injection pulse to generate electron beams with large charge and low energy spread. In this manner, an electron beam with 0.1% energy spread, 214   p C total charge and 0.3 π   m m ⋅ m r a d emittance can be produced.