神光Ⅱ升级激光装置基频输出能力提升

Improvement of fundamental frequency performance of SGII-UP laser facility

神光Ⅱ升级装置是国际上为数不多常年运行的惯性约束核聚变激光装置,为进一步提升其输出能力以满足更高物理需求,采用新型钕玻璃,并结合增加钕玻璃数、提高氙灯能源配置等措施来提升主放大器的增益能力.改进后的测试表明装置的平均小信号增益系数从4.15%cm增至4.94%cm,单路小信号增益倍数从9000提升到118000,提升幅度超过了1个数量级,有效降低了高通量下非线性相移引起的激光近场小尺寸调制,提升了装置基频输出能力,为实现更高的打靶能量奠定关键基础.运行打靶验证了装置高峰值功率下基频近场调制的改善,以及10 ns脉冲12.5 kJ的基频输出能力,有力支撑了高通量要求的物理实验目标.

The SGII-UP laser facility is one of the most important high power laser systems in China,and it is also one of a few inertial confinement fusion laser devices that operate all year round in the world.In order to further improve its output capacity to meet higher physical requirements,measures such as increasing the number of neodymium glasses,adopting new N41 neodymium glasses,and improving the energy configuration of xenon lamps are taken to improve the gain capacity of the main amplifier.Calculation of the new main amplifier construction model predicts that the small gain coefficient will reach 4.9%.And further modulation of the laser device shows that when the output of 10 kJ fundamental frequency energy is needed,the injection energy decreases from 5 J to 1.26 J,which supports a higher output energy and a stronger basic frequency output capability.Furthermore,it is analyzed that under different laser pulse injection conditions of 1,5,10 ns,the B integral is obviously reduced,which means that the near-filed quality of the beams is better.According a small-size modulation suppression is induced by nonlinear phase shift,and high-fluence laser is expected to pass before and after the improvement,which is a key prerequisite for a higher output energy.Based on these analyses,fundamental frequency output energy values with different pulse injections are calculated and an improvement from 8 kJ to 12.5 kJ output is expected under 10 ns square pulse condition.Tests show that the small signal gain coefficient of the device increases from 4.15%cm to 4.94%cm,which is consistent with simulation results,and the average gain multiple of a single beam increases from 9000 to 118000,which is an order of magnitude higher.The output verifies the fundamental frequency output capacity exceeding 12.5 kJ under 10 ns square pulse as well as a small-size modulation suppression around 0.16 mm^(−1) as a result of joint action of non-linear phase shift and spatial filtering.After the significant improvement,the SGII-UP laser facility will strongly support more ambitious physical experiment targets.