Mie scattering from submicron-sized CO_2 clusters formed in a supersonic expansion of a gas mixture

Abstract

A detailed mathematical model is presented for a submicron-sized cluster formation in a binary gas mixture flowing through a three-staged conical nozzle. By measuring the angular distribution of light scattered from the clusters, the size of CO(2) clusters, produced in a supersonic expansion of the mixture gas of CO(2)(30%)/H(2)(70%) or CO(2)(10%)/He(90%), has been evaluated using the Mie scattering method. The mean sizes of CO(2) clusters are estimated to be 0.28 ± 0.03 μm for CO(2)/H(2) and 0.26 ± 0.04 μm for CO(2)/He, respectively. In addition, total gas density profiles in radial direction of the gas jet, measuring the phase shift of the light passing through the target by utilizing an interferometer, are found to be agreed with the numerical modeling within a factor of two. The dryness (= monomer/(monomer + cluster) ratio) in the targets is found to support the numerical modeling. The apparatus developed to evaluate the cluster-gas targets proved that our mathematical model of cluster formation is reliable enough for the binary gas mixture.

Investigation of the on-axis atom number density in the supersonic gas jet under high gas backing pressure by simulation

“…The capability of this model for the gas density has been demonstrated. 19,21,23 In this work, the gas jets of eighteen conical nozzles with the same throat diameter d of 0.5 mm under five gas backing pressures were simulated for the on-axis atom number density. As examples, the results about density at the gas backing pressure of 50 bars are shown in Fig.…”

The radial dimension of a supersonic jet expansion from conical nozzle

“…The capability of this model for the spatial distribution of gas density has been demonstrated. 16,18,19 The 2D hydrodynamic model reproduces the spatial structure of the gas jet, including the rarefaction waves at the edges of the jet, and it is possible to evaluate the diameter on the base of the simulated results by introducing a threshold density value. Similarly to the definition of gas diameter in Ref.…”

“…3,4 The production of a gas jet and its characterization have attracted interests and been extensively studied. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Usually, a supersonic clustered gas jet can be produced by the adiabatic expansion of gas under a high backing pressure through a conical nozzle into vacuum. The dimension of a gas jet is an important parameter for the determination of interaction length.…”

Mathematical modelling of the cluster targets for femtosecondlaser-cluster-driven experiments

“…Для больших (субмикронного размера) кластеров (которые получаются с помощью специально сконструированного сопла) можно использовать экспериментальные методики на основе рассеяния Ми вместо рэлеевского рассеяния [38,39]. Это позволяет непосредственно получить средний размер кластера и его среднеквадратичное отклонение (но в предположении, что распределение кластеров по размерам логарифмически нормальное).…”

“…Была предложена математическая модель [40,41,60], основанная на представлении кластеров как сферических микрокапель и на кинетической теории Я. И. Френкеля [61,62]. Позже эта модель была обобщена на случай бинарных смесей газов, в которых одна компонента не образует кластеров [38]. По результатам моделирования оказалось, что бинарные смеси могут обеспечить высокую степень кластеризации кластеризующейся компоненты, причем газ между кластерами состоит главным образом из инертной компоненты.…”