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The spherically convergent plasma fusion (SCPF) scheme is a robust approach to provide a high-brightness pulsed neutron source. The performance of the SCPF driven by the long-pulsed laser is investigated. The experiments, with the laser pulse duration in a range of 0.5 ns to 3 ns, were implemented on the ShenGuang-II Upgrade facility and a 100 kJ level laser facility. The intensity of the laser beam was about multiple 1014 W cm−2. The measured D–D reaction neutron yields were in a range of 7.3 × 108 to 1.01 × 1011, while the driven laser energies were in a range of 2.1 kJ to 100.5 kJ. The temporal self-emitted x-ray flux and image were measured. It showed that the plasma core could be maintained for a longer time in the long duration shots. The neutron reaction rate was measured on the 100 kJ level laser facility. The full width at half maximum reached about 1 ns in the shot with 2 ns duration laser. The scaling law of the measured yields with respect to the laser power and the pulse duration were presented. The neutron yield was able to be increased by increasing the power and extending the duration.

The influence of low-mode-driven asymmetry on yield degradation in shaped-pulse indirect-drive implosions has been investigated at the 100 kJ laser facility. In this work, P2- and P4-driven asymmetries were tuned by varying hohlraum gas-fill density and capsule diameter. The measured neutron yield varied from 2.1 × 109 to 7.6 × 109 and the yield measured by a 1D simulation (YOC1D) was increased from 3% to 16%. Meanwhile, considering the temporal P2- and P4-driven asymmetries, the yields measured by 2D simulations (YOC2D) were from 26% to 81% (the YOC2D of the majority of the shots was higher than 50%). Furthermore, both the ion temperature and neutron bang-time showed good agreement between the measurements and the 2D simulations. The simulations demonstrated that the temporal P2- and P4-driven asymmetries can decrease the efficiency of PdV work and increase the energy loss due to electron thermal conduction. In addition, the internal energy of the deuterium (DD) fuel clearly decreased and the neutron yield was degraded by low-mode asymmetry. In a future work, we will enlarge the cylindrical hohlraum diameter or use an I-hohlraum to improve the low-mode-driven symmetry, along with measurement of the hot-spot shape.

The anomalous mix at the high-Z and low-Z plasma interfaces in an inertial confinement fusion hohlraum is a current topic of interest. The mechanism for such an anomalous mix in the interpenetration layer at the high-Z and low-Z plasma interface and its effects on the laser plasma instabilities have been investigated by particle-in-cell simulations. It is found that a diffusion-driven collisionless shock wave can be generated from an initially sharp high-Z and low-Z plasma interface with total pressure balance and constant temperature in the laser propagation channel. This purely electrostatic shock wave propagates into the high-Z plasma and leads to mix of different species of ions which is significantly faster than a classical mix in the presence of the large electric field. The mix layer width, measured as a separation distance affected by the shock, grows as , where . The effect of the anomalous mix on the linear growth rate of laser plasma instabilities is evaluated.