Flux waveforms of aluminum cluster beams supplied from a laser-ablation cluster source were precisely investigated under various source conditions such as background pressure, ablation laser intensity, and nozzle structure. A time-of-flight mass spectroscopy revealed that aluminum clusters with sizes up to 200 were generated and the amount of the clusters could be maximized by choosing a proper background pressure (~2 MPa) and an ablation laser fluence (~40 mJ/cm2). Flux waveforms of clusters having specific sizes were carefully reconstructed from the observed mass spectra. It is found that the pulse widths of the aluminum cluster beams were typically about 100 µs and much smaller than that of the monoatomic aluminum beam, indicating that the cluster formation was limited in a relatively small volume in the laser-ablated vapor. Introducing a conical nozzle having a large open angle was also found to enhance the cluster beam velocity and reduce its pulse width. A velocity measurement of particles in the cluster beam was conducted to examine the velocity spread of the supplied clusters. We found that the aluminum clusters were continuously released from the source for about 100 µs and this release time mainly determined the pulse width of the cluster beam, suggesting that controlling the behavior of an ablated vapor plume in the waiting room of the cluster source holds the key to drastically improving the cluster beam flux.

中文翻译：

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来自激光烧蚀金属团簇源的质量分离粒子通量

在背景压力，烧蚀激光强度和喷嘴结构等各种辐射源条件下，精确研究了激光烧蚀簇源提供的铝簇束的通量波形。飞行时间质谱分析显示，生成了尺寸最大为200的铝簇，并且可以通过选择适当的背景压力（〜2 MPa）和消融激光能量密度（〜40 mJ / cm）来最大化簇的数量2个）。从观察到的质谱图中仔细重建了具有特定大小的簇的通量波形。发现铝簇束的脉冲宽度通常为约100μs，并且比单原子铝束的脉冲宽度小得多，这表明簇的形成被限制在激光烧蚀的蒸气中的相对较小的体积中。还发现引入具有大开角的圆锥形喷嘴可增强簇束速度并减小其脉冲宽度。进行簇束中粒子的速度测量以检查所提供簇的速度分布。我们发现铝团簇从源中连续释放约100 µs，而这个释放时间主要决定了团簇束的脉冲宽度，