Abstract <p>At the SRC RF TRINITI (Moscow, Troitsk), a plasma gun with a new gas injection system is being developed as part of the task of creating a neutron source. In the new injection system, gas is injected into the working volume using fast-acting valves in the direction from the outer to the inner electrode. This establishes the gas distribution with the increased density near the central electrode. A Laval nozzle is used to achieve azimuthal uniformity of the flow. The objective of this work has been to study the plasma-forming gas injection into the interelectrode gap of the new plasma gun. In the course of the study, a numerical model of the injection system has been developed. The hydrodynamic equation system is solved using the finite volume method on a moving mesh, which made it possible to take into account the motion of the gas valve stem. The gas-dynamic variables on the next time layer are calculated using an implicit scheme. The gas pressure distribution in the interelectrode gap is measured with pressure transducers, and the gas flow parameters are estimated. Based on the results obtained, the numerical model is validated. The developed numerical model adequately describes the behavior of the gas flow in the interelectrode gap.</p>