Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299, USA.
Rev Sci Instrum. 2023 May 1;94(5). doi: 10.1063/5.0101839.
The sub-aperture backscatter (SABS) diagnostic on the OMEGA EP Laser System [Waxer et al., Opt. Photonics News 16, 30 (2005)] is a diagnostic that is used to measure the backscattered and sidescattered light during laser-plasma interaction experiments [W. L. Kruer, The Physics of Laser Plasma Interactions, Frontiers in Physics Vol. 73, edited by D. Pines (Addison-Wesley, Redwood City, CA, 1988) and Myatt et al., Phys. Plasmas 21, 055501 (2014)] that are relevant to high-energy-density physics and inertial confinement fusion. The diagnostic collects stimulated Brillouin scattering (SBS) UV light at around 351 nm and stimulated Raman scattering (SRS) in the visible-light regime in the 420-720-nm-wavelength range and provides spectrally and temporally resolved information. Five 1-in. light collectors, composed of a lens, ground glass diffuser, and coupling into a 300-μm fiber, are positioned behind the last steering mirror on one of the four beamlines to catch a portion of the beam cross section (∼1.5%) of the emission that is scattered into the beamline. The SRS light is collected in two light collectors, combined, and transported via graded index fibers to a streaked spectrometer. The SABS-SRS streak spectrometer has a temporal and spectral resolution of 100 ps and 1 nm, respectively. Three other light collectors collect, combine, and transport the SBS signal to a Hamamatsu high-voltage photodiode, where an oscilloscope digitizes the data, providing a time resolution of better than 1 ns. To obtain an absolute energy calibration of SRS measurements, light signals of known energy and wavelength were injected into the light collectors one at a time. The resulting counts on the streak camera charge-coupled device for SRS are then correlated with the incident fluence of scattered light at the light collector in order to allow a quantitative assessment of streak camera sensitivity to determine the energy of the scattered light during experiments. The measurements were performed in situ from the light collectors to the detectors. Additional offline measurements provided the transmission of the optics between the target chamber center and the light collectors.
OMEGA EP 激光系统上的子孔径后向散射 (SABS) 诊断[Waxer 等人，《光学与光子学新闻》16,30（2005）]是一种用于测量激光等离子体相互作用实验中后向散射和侧向散射光的诊断方法[W. L. Kruer，《激光等离子体相互作用物理学》，第 73 卷，《物理学前沿》，由 D. Pines 编辑（Addison-Wesley，Redwood City，CA，1988）和 Myatt 等人，《物理评论》等离子体 21,055501（2014）]，这些实验与高能密度物理学和惯性约束聚变有关。该诊断系统收集在 351nm 左右的受激布里渊散射 (SBS) UV 光和在可见光谱范围内的 420-720nm 波长范围内的受激拉曼散射 (SRS)，并提供光谱和时间分辨信息。五个 1 英寸的集光器，由透镜、磨砂玻璃扩散器和耦合到 300μm 光纤组成，位于其中一个光束线上的最后一个转向镜后面的位置，以捕捉发射光束横截面的一部分（约 1.5%），这些发射光束被散射到光束线中。SRS 光被两个集光器收集，组合，并通过梯度折射率光纤传输到条纹分光计。SABS-SRS 条纹分光计的时间分辨率和光谱分辨率分别为 100ps 和 1nm。另外三个集光器收集、组合并传输 SBS 信号到 Hamamatsu 高压光电二极管，其中示波器对数据进行数字化，时间分辨率优于 1ns。为了对 SRS 测量进行绝对能量校准，将已知能量和波长的光信号逐个注入集光器。然后，条纹相机 CCD 上的 SRS 计数与集光器上散射光的入射通量相关联，以便对条纹相机的灵敏度进行定量评估，从而确定实验过程中散射光的能量。测量是在从集光器到探测器的原位进行的。附加的离线测量提供了靶室中心和集光器之间的光学元件的传输。
