Bennett G R, Smith I C, Shores J E, Sinars D B, Robertson G, Atherton B W, Jones M C, Porter J L
Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1193, USA.
Rev Sci Instrum. 2008 Oct;79(10):10E914. doi: 10.1063/1.2956823.
When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26 MA Z Accelerator, the terawatt-class, multikilojoule, 526.57 nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151 keV (1s(2)-1s2p triplet line of He-like Mn) curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004); G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)], is capable of providing a high quality x radiograph per Z shot for inertial confinement fusion (ICF), complex hydrodynamics, and other high-energy-density physics experiments. For example, this diagnostic has recently afforded microgram-scale mass perturbation measurements on an imploding ignition-scale 1 mg ICF capsule [G. R. Bennett et al., Phys. Rev. Lett. 99, 205003 (2007)], where the perturbation was initiated by a surrogate deuterium-tritium (DT) fuel fill tube. Using an angle-time multiplexing technique, ZBL now has the capability to provide two spatially and temporally separated foci in the Z chamber, allowing "two-frame" imaging to be performed, with an interframe time range of 2-20 ns. This multiplexing technique allows the full area of the four-pass amplifiers to be used for the two pulses, rather than split the amplifiers effectively into two rectangular sections, with one leg delayed with respect to the other, which would otherwise double the power imposed onto the various optics thereby halving the damage threshold, for the same irradiance on target. The 6.151 keV two frame technique has recently been used to image imploding wire arrays, using a 7.3 ns interframe time. The diagnostic will soon be converted to operate with p-rather than s-polarized laser light for enhanced laser absorption in the Mn foil, plus other changes (e.g., operation at the possibly brighter 6.181 keV Mn 1s(2)-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast (1 ns gate time) digital x-ray camera is being developed [G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)] to extend the system to "four-frame" and markedly improve the signal-to-noise ratio. [At present, time-integrating Fuji BAS-TR2025 image plate (scanned with a Fuji BAS-5000 device) forms the time-integrated image-plane detector.].
桑迪亚国家实验室最近升级的26兆安Z加速器用于产生X射线成像背光源时，太瓦级、多千焦、526.57纳米的Z光束激光（ZBL）[P.K.兰博等人，《应用光学》44，2421（2005）]，与6.151千电子伏（类氦锰的1s(2)-1s2p三线态谱线）弯曲晶体成像仪[D.B.西纳尔斯等人，《科学仪器评论》75，3672（2004）；G.R.贝内特等人，《科学仪器评论》77，10E322（2006）]相结合，能够在每次Z脉冲时为惯性约束聚变（ICF）、复杂流体动力学及其他高能密度物理实验提供高质量的X射线照片。例如，这种诊断方法最近在一个内爆点火规模的1毫克ICF胶囊上实现了微克级质量扰动测量[G.R.贝内特等人，《物理评论快报》99，205003（2007）]，其中扰动由替代氘 - 氚（DT）燃料填充管引发。利用角度 - 时间复用技术，ZBL现在有能力在Z腔室内提供两个空间和时间上分离的焦点，从而能够进行“两帧”成像，帧间时间范围为2 - 20纳秒。这种复用技术允许将四程放大器的整个区域用于两个脉冲，而不是有效地将放大器分成两个矩形部分，其中一个支路相对于另一个支路延迟，否则对于相同的靶面辐照度，施加到各种光学元件上的功率将加倍，从而使损伤阈值减半。6.151千电子伏两帧技术最近已用于对内爆丝阵进行成像，帧间时间为7.3纳秒。该诊断方法很快将转换为使用p偏振而非s偏振激光，以增强在锰箔中的激光吸收，同时还有其他变化（例如，在可能更亮的6.181千电子伏锰的1s(2)-1s2p单线态谱线处运行），以提高X射线产量。此外，正在开发一种高灵敏度的在线多帧超快（1纳秒门控时间）数字X射线相机[G.R.贝内特等人，《科学仪器评论》77，10E322（2006）]，以将系统扩展到“四帧”并显著提高信噪比。[目前，时间积分富士BAS - TR2025成像板（用富士BAS - 5000设备扫描）构成时间积分像平面探测器。]
