Meyer H J, Bruulsema C, Tubman E R, Swadling G F, Moody J D, Lemos N, Ross J S
Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550, USA.
Department of Physics, Imperial College London, Exhibition Rd., South Kensington, London SW7 2AZ, United Kingdom.
Rev Sci Instrum. 2024 Sep 1;95(9). doi: 10.1063/5.0219559.
A rapid calibration system is under development for the Near Backscatter Imager (NBI) in use at the National Ignition Facility (NIF). NBI is an optical diagnostic that quantifies the stimulated Brillouin and Raman backscatter produced by NIF's targets. Specifically, NBI measures the light that does not fall directly back into the laser aperture, which is measured by the Full Aperture Backscatter System (FABS). When working in tandem with FABS, NBI allows for the full characterization of backscattered light. This informs Hohlraum laser coupling, optical damage, and laser-plasma interaction models. NBI uses a large Spectralon plate covered by a protective glass layer and is mounted inside the target chamber where it is exposed to high energy backscatter, neutrons, and build-up debris left over from the exploded targets. This gradually alters the reflectivity of the plate, meaning that NBI needs to be calibrated regularly. Described here is NIF's design for a system capable of rapid in situ calibration of NBI that is to be installed in FY25.
国家点火装置（NIF）正在为其使用的近背向散射成像仪（NBI）开发一种快速校准系统。NBI是一种光学诊断设备，用于量化由NIF靶产生的受激布里渊和拉曼背向散射。具体而言，NBI测量不会直接返回激光孔径的光，该光由全孔径背向散射系统（FABS）进行测量。当与FABS协同工作时，NBI能够对背向散射光进行全面表征。这为黑腔激光耦合、光学损伤和激光 - 等离子体相互作用模型提供了信息。NBI使用一块覆盖有保护玻璃层的大型Spectralon板，该板安装在靶室内，在那里它会受到高能背向散射、中子以及爆炸靶留下的累积碎片的影响。这会逐渐改变该板的反射率，这意味着NBI需要定期进行校准。这里描述的是NIF为一个能够对NBI进行快速原位校准的系统所做的设计，该系统将于2025财年安装。
