Abstract
In a laser-cluster interaction experiment, the radial dimension of a supersonic gas jet is an important parameter for the characterization of interaction volume. It is noted that due to the lateral gas expansion, the diameter of a supersonic gas jet is larger than the idealized diameter of a gas jet from a conical nozzle. In this work the effect of the lateral expansion on the radial dimension of gas jet was investigated by simulations. Based on the simulation results, the diameter of gas jet l was compared in detail with the corresponding diameter lT in the idealized straight streamline model and the diameter lH at a half of maximum atom density of gas jet. The results reveal how the deviation of l from lT (lH) changes with respect to the opening angles of conical nozzles, the heights above the nozzle, the nozzle lengths and the gas backing pressures. It is found that the diameter of gas jet l is close to the idealized diameter lT and lH in the case where a long conical nozzle with a large opening angle is used under a low gas backing pressure. In this case, the effect of the lateral expansion is so weak that the edge of gas jet becomes sharp and the radial distribution of atom density in gas jet tends to be uniform. The results could be useful for the characterization of a supersonic gas jet.
Highlights
Because there is no effect of the lateral gas expansion in the straight streamline model, the ratio of the gas jet dimension from simulation to that in the straight streamline model can be used to study the effect of the lateral expansion
It is found that the bigger the opening angle or the higher the height is, the larger the diameter of gas jet is for a given nozzle length
By simulations, we investigated the dependence of the diameter ratio of a gas jet on the opening angle, the nozzle length of a conical nozzle, the height above the nozzle and the gas backing pressure
Summary
The dependence of the diameter ratio on these parameters is similar to that of the on-axis atom density on these parameters.[21,22] Due to the lateral expansion, the diameters l, lT and lH are usually different. They tend to be the same only when the conical nozzle with a long nozzle length and a large opening angle is used under a low backing pressure. A long conical nozzle of a large opening angle could be used to produce a supersonic gas jet with the uniform radial atom density distribution, even at high gas backing pressure. The results could be helpful for the characterization of a gas jet in the study of laser-cluster interaction
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