近日，美国罗彻斯特大学的C. A. Williams及其研究团队取得一项新进展。经过不懈努力，他们成功论证直接驱动惯性约束聚变内爆中热点燃料增益超过1。相关研究成果已于2024年2月5日在国际知名学术期刊《自然—物理学》上发表。

该研究团队报道了一项激光直接驱动实验，并发现聚变反应释放的能量超过了中心热点等离子体产生的能量。这一发现表明，所谓的“热点”燃料增益大于1，且增益值约为4。值得注意的是，在国家点火装置进行的间接驱动惯性约束聚变实验中，太空舱是通过X射线照射的，所需的激光能量高达1.9MJ。

相比之下，研究人员在OMEGA激光系统上的实验仅需28kJ，显著降低了能量需求。随着激光能量和靶尺寸的增大，预计热点燃料增益将进一步提高。这一研究为惯性聚变的直接驱动方法奠定了基础，被认为是实验室中燃烧和点燃等离子体的一种有前途的途径。此外，研究人员还在OMEGA系统上实现了创纪录的直接驱动聚变产率，高达0.9kJ，这是通过使用薄冰氘-氚衬里靶实现的。

据悉，用强激光直接照射一个装有氘和氚燃料的小胶囊，会导致它内爆，从而产生足够热的等离子体，引发燃料原子核之间的聚变反应。。

附：英文原文

Title: Demonstration of hot-spot fuel gain exceeding unity in direct-drive inertial confinement fusion implosions

Author: Williams, C. A., Betti, R., Gopalaswamy, V., Knauer, J. P., Forrest, C. J., Lees, A., Ejaz, R., Farmakis, P. S., Cao, D., Radha, P. B., Anderson, K. S., Regan, S. P., Glebov, V. Yu, Shah, R. C., Stoeckl, C., Ivancic, S., Churnetski, K., Janezic, R. T., Fella, C., Rosenberg, M. J., Bonino, M. J., Harding, D. R., Shmayda, W. T., Carroll-Nellenback, J., Hu, S. X., Epstein, R., Collins, T. J. B., Thomas, C. A., Igumenshchev, I. V., Goncharov, V. N., Theobald, W., Woo, K. M., Marozas, J. A., Bauer, K. A., Sampat, S., Waxer, L. J., Turnbull, D., Heuer, P. V., McClow, H., Ceurvorst, L., Scullin, W., Edgell, D. H., Koch, M., Bredesen, D., Johnson, M. Gatu, Frenje, J. A., Petrasso, R. D., Shuldberg, C., Farrell, M., Murray, J., Guzman, D., Serrato, B., Morse, S. F. B., Labuzeta, M., Deeney, C., Campbell, E. M.

Issue&Volume: 2024-02-05

Abstract: Irradiating a small capsule containing deuterium and tritium fuel directly with intense laser light causes it to implode, which creates a plasma hot enough to initiate fusion reactions between the fuel nuclei. Here we report on such laser direct-drive experiments and observe that the fusion reactions produce more energy than the amount of energy in the central so-called hot-spot plasma. This condition is identified as having a hot-spot fuel gain greater than unity. A hot-spot fuel gain of around four was previously accomplished at the National Ignition Facility in indirect-drive inertial confinement fusion experiments where the capsule is irradiated by X-rays. In that case, up to 1.9MJ of laser energy was used, but in contrast, our experiments on the OMEGA laser system require as little as 28kJ. As the hot-spot fuel gain is predicted to grow with laser energy and target size, our work establishes the direct-drive approach to inertial fusion as a promising path towards burning and ignited plasmas in the laboratory. Additionally, we report a record (direct-drive) fusion yield of 0.9kJ on OMEGA, which we achieved with thin-ice deuterium–tritium liner targets.

DOI: 10.1038/s41567-023-02363-2

Source: https://www.nature.com/articles/s41567-023-02363-2