Threshold for Switching the Dynamic Pressure Dependence of Plasma Propagation Velocity

The dependence of plasma propagation velocity on the force applied to the plasma bullet is investigated. The force applied to the plasma bullet is composed of the dynamic pressure with AC electric field and the collision with the neutral gas flow. Three cases are observed in the experimental results: directly proportional, inversely proportional, and non-proportional to the ponderomotive parameters at each dynamic pressure due to the helium gas flow. In the directly proportional case, the applied force is inversely proportional to the frequency of the applied voltage. When the blank period is shorter than the application time of the voltage, the next electromagnetic energy of the applied force is added to the residual plasma energy and the plasma propagation velocity is directly proportional to the frequency of the applied voltage. Consequently, in the inversely proportional case, the applied voltage is directly proportional to the frequency of the applied voltage. In the non-proportional case, the plasma propagation velocity depends on the dynamic pressure due to the helium gas flow. When the strength of the applied voltage is low, the plasma propagation velocity is proportional to the dynamic pressure due to the helium gas flow over a wide range of dynamic pressure. While, when the strength of the applied voltage is high, the plasma propagation velocity is non-proportional to the dynamic pressure due to the helium gas flow. Therefore, it is possible to investigate the threshold of the dynamic pressure at which the velocity dependence changes.