Challenge for continuous operation of extreme ultra-violet light source using hypersonic jet

为了制作可控束流靶，在真空中准连续地形成了超声波定域射流。 建立了由微型拉瓦尔喷嘴、气体靶室和超声速扩压器组成的装置，用于研究气体靶的形成以及喷嘴和扩压器流动的气体动力学研究。结果表明，对于自由射流的连续运行，扩压器的优化是至关重要的。我们测量了超音速喷管中的静压分布，它是滞止压力和喷管几何形状的函数，表明了非平衡凝结对压力分布的影响。基于喷嘴流动实验和考虑凝结过程的数值模型，提出了一种预测核化和团簇形成过程的半经验方法。 该模型可以从非平衡凝结流的压力分布来表征凝结的过饱和状态和凝结开始。

In order to make a controllable beam target, a hyper-sonic localized jet was formed quasi-continuously in vacuum. An apparatus composed of a miniature Laval nozzle, a gas target chamber, and a supersonic diffuser was constructed for studies on the gas target formation and the gas-dynamical study on the nozzle and diffuser flows. Results showed, for continuous operation of the free-jet flow, diffuser optimization is critically important. We measured static pressure profiles in the supersonic nozzle as a function of the stagnation pressure and the nozzle geometry, which indicated effects of non-equilibrium condensation on the pressure profiles. We proposed a semi-empirical method to predict the nucleation and cluster formation processes based on the nozzle flow experiments and a numerical model considering the condensation process. The model could characterize the supersaturated states and onset of the condensation from the pressure profiles of the non-equilibrium condensation flow.