Simulation study on gas targets applied to underdense plasma generation

Numerical simulations and analyses are done on two types of gas targets by using a computational fluid-dynamics software. For a gas-filling capillary, a stable laminar flow can be formed. It can produce a uniform density distribution and the nonuniformity between the two inlets is only 1%. The capillary parameters such as the capillary’s inlet locations and the inlet width have evident influence on the density profiles around the capillary’s ends, but negligible on the density-profile distributions inside the capillary. For a conical gas jet, it can make the end-density profile steeper than that of the capillary. But the supersonic flow of the gas jet may cause turbulence, which may cause the gas flow unstable and the gas-density profile less uniform.