Two types of plasma channel structure in high pressure pulse discharge in cesium

Simulation of the pulse-periodic high pressure cesium discharge is performed on the basis of equations of radiative gas dynamics. It is shown that in the discharge it is possible to implement two different types of structure of the plasma channel. At the beginning of the current pulse, the plasma discharge channel has a centered structure. At the same time, most of the plasma is concentrated near the discharge axis. The concentration of charged particles decreases along the radius.Then, if the current amplitude is large enough, during the plasma heating process, a transformation from the centered to the shell structure of the channel occurs. In this case, most of the plasma is concentrated on the periphery of the discharge and its concentration increases along the radius from the axis to the walls of the tube. It is shown that the transition from one channel structure to another occurs at a time when the specific heat capacity of the plasma near the axis reaches a deep minimum corresponding to a completely single ionized $e$–$i$ plasma.