MacDonald M J, Gorkhover T, Bachmann B, Bucher M, Carron S, Coffee R N, Drake R P, Ferguson K R, Fletcher L B, Gamboa E J, Glenzer S H, Göde S, Hau-Riege S P, Kraus D, Krzywinski J, Levitan A L, Meiwes-Broer K-H, O'Grady C P, Osipov T, Pardini T, Peltz C, Skruszewicz S, Swiggers M, Bostedt C, Fennel T, Döppner T
University of Michigan, Ann Arbor, Michigan 48109, USA.
SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Rev Sci Instrum. 2016 Nov;87(11):11E709. doi: 10.1063/1.4960502.
Atomic clusters can serve as ideal model systems for exploring ultrafast (∼100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano-plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities, and ionization. Single shot x-ray Thomson scattering signals were recorded at 120 Hz using a crystal spectrometer in combination with a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. Such measurements are important for understanding collective effects in laser-matter interactions on femtosecond time scales, opening new routes for the development of schemes for their ultrafast control.
原子团簇可作为理想的模型系统，用于探索纳米尺度上致密物质的超快（约100飞秒）激光驱动电离动力学。在接近固体密度条件下，光学激光脉冲的共振吸收能够将温度加热到约1千电子伏特。迄今为止，对这种纳米等离子体瞬态的直接探测仅限于相干X射线成像。在此，我们首次展示了对团簇进行光谱分辨的非相干X射线散射测量，从而能够测量瞬态温度、密度和电离情况。使用晶体光谱仪结合单光子计数和能量色散pnCCD，以120赫兹的频率记录了单次X射线汤姆逊散射信号。一种精确的泵浦激光准直方案使得能够以前所未有的超过3个数量级的动态范围记录来自氩团簇的近无背景散射光谱。此类测量对于理解飞秒时间尺度上激光与物质相互作用中的集体效应非常重要，为其超快控制方案的开发开辟了新途径。
