Plasma current regulated by balance between driving and restricting forces

Abstract

In many plasma applications, the plasma current, which is determined by the plasma density and drift velocity, is an important parameter when investigating the induced phenomenon and its effects. However, it is unclear which physical parameters are responsible for regulating the current. Plasma is generated by a balance between the driving and restricting forces. The driving force originates from the electric and magnetic fields, and the restricting force originates from collisions between different species (electrons, ions, and neutral particles). When the electric field fluctuates over time, the pressure of the driving force is generated. The pressure of the driving force depends on the square of the electric field and the reciprocal of the repetition frequency. The pressure of the restricting force depends on the gas flow velocity and the collision frequency. When electrons and/or ions flow with the flowing neutral gas, a plasma current is generated from flowing charged particles. The magnitude of the plasma current is linearly proportional to the pressure caused by the driving force, and the variation in the plasma current depends on the pressure caused by the restricting force. In addition, the plasma current varies with the applied period of the voltage. Consequently, the plasma charge, which is the time integral of the plasma current, shows a linear relationship with the driving force and is thus regulated by the force balance between the driving and restricting forces. Therefore, the plasma current value and its generation time are regulated by the strength, applied period, and repetition frequency of the applied voltage and the neutral gas flow velocity.