First polar direct-drive exploding-pusher target experiments on the ShenGuang laser facility

Low density and low convergence implosion occurs in the exploding-pusher target experiment, and generates neutrons isotropically to develop a high yield platform. In order to validate the performance of ShenGuang (SG) laser facility and test nuclear diagnostics, all 48-beam lasers with an on-target energy of 48 kJ were firstly used to drive room-temperature, DT gas-filled glass targets. The optimization has been carried out and optimal drive uniformity was obtained by the combination of beam repointing and target. The final irradiation uniformity of less than 5% on polar direct-drive capsules of $540\mu m$ in diameter was achieved, and the highest thermonuclear yield of the polar direct-drive DT fuel implosion at the SG was 1.04×10¹³. The experiment results show neutron yields severely depend on the irradiation uniformity and laser timing, and decrease with the increase of the diameter and fuel pressure of the target. The thin CH ablator does not impact the implosion performance, but the laser drive uniformity is important. The simulated results validate that the $\cos \gamma$ distribution laser design is reasonable and can achieve a symmetric pressure distribution. Further optimization will focus on measuring the symmetry of the hot spot by self-emission imaging, increasing the diameter, and decreasing the fuel pressure. (paper)