Opachich Y P, Palmer N, Homoelle D, Hatch B, Bell P, Bradley D, Kalantar D, Browning D, Zuegel J, Landen O
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Rev Sci Instrum. 2012 Oct;83(10):10E123. doi: 10.1063/1.4732855.
The convergent ablator experiments at the National Ignition Facility (NIF) are designed to measure the peak velocity and remaining ablator mass of an indirectly driven imploding capsule. Such a measurement can be performed using an x-ray source to backlight the capsule and an x-ray streak camera to record the capsule as it implodes. The ultimate goal of this experiment is to achieve an accuracy of 2% in the velocity measurement, which translates to a ±2 ps temporal accuracy over any 300 ps interval for the streak camera. In order to achieve this, a 4ω (263 nm) temporal fiducial system has been implemented for the x-ray streak camera at NIF. Aluminum, titanium, gold, and silver photocathode materials have been tested. Aluminum showed the highest relative quantum efficiency, with five times more peak signal counts per fiducial pulse when compared to Gold. The fiducial pulse data were analyzed to determine the centroiding statistical accuracy for incident laser pulse energies of 1 and 10 nJ, showing an accuracy of ±1.6 ps and ±0.7 ps, respectively.
国家点火装置（NIF）的会聚烧蚀体实验旨在测量间接驱动内爆靶丸的峰值速度和剩余烧蚀体质量。可以使用X射线源对靶丸进行背光照明，并使用X射线条纹相机记录靶丸内爆过程，从而进行此类测量。该实验的最终目标是在速度测量中达到2%的精度，这意味着条纹相机在任何300皮秒间隔内的时间精度为±2皮秒。为了实现这一目标，NIF为X射线条纹相机实施了一个4ω（263纳米）时间基准系统。已经测试了铝、钛、金和银光电阴极材料。铝显示出最高的相对量子效率，与金相比，每个基准脉冲的峰值信号计数多五倍。对基准脉冲数据进行了分析，以确定入射激光脉冲能量为1纳焦和10纳焦时的质心统计精度，分别显示出±1.6皮秒和±0.7皮秒的精度。
