Hagena团簇尺度定律中锥形喷嘴的等效孔径

The equivalent diameter of conical nozzle in Hagena scaling laws

本文首先详细重演了锥形喷嘴的等效孔径deq,并根据deq的定义给出了它与气体团簇喷流的径向宽度之间的依赖关系.然后以高背压氩气团簇喷流为例,通过成像喷流的Rayleigh散射光的空间分布研究了不同背压下喷流的径向宽度,并与Hagena团簇尺度定律中直线流模型假设的喷流径向宽度进行了比较.结果表明,Hagena直线流模型假设的喷流径向宽度小于实际的径向宽度,且实际宽度与气体背压有关.进一步的研究表明,直线流模型对喷流宽度的估计偏差导致对锥形喷嘴等效孔径的估计偏差,这为Hagena尺度定律估计团簇平均尺寸的偏差给出了一种可能的解释.

The cluster size is an important parameter in the study on the interaction of intense laser pulse with cluster jet produced by the gas adiabatic expansion through a nozzle into vacuum. The Hagena scaling law is usually used to estimate the average cluster size. However, there is the deviation of average cluster size from the prediction by the scaling law in the case that the conical nozzle is used at the high gas backing pressure. In this work, firstly the equivalent diameter of conical nozzle is re-calculated in detail, and then the relation between deq and the radial dimension of the cluster jet is obtained. As an example, the images of Rayleigh scattering light by argon cluster jet at different backing pressures are recorded to investigate the dimensions of cluster jet. And then the corresponding theoretical dimensions based on the idealized straight streamline model in the scaling law are compared with the experimental dimensions. It is found that the experimental dimension is larger than the theoretical one, and is related to the gas backing pressure. This under-estimation of theoretical cluster jet dimension leads to the over-estimation of the equivalent diameter of conical nozzle which is responsible for the cluster size deviation in Hagena scaling laws.