Two-surface multipactor and plasma discharges in a parallel-plate microwave system

In this work, we investigate multipactor discharges within two parallel plates with an external circuit consisting of a resistor (R), an inductor (L), a capacitor (C). The RLC circuit and two parallel plates represent a microwave system. At low pressure, the discharge mode gradually transitions from multipactor to plasma. In vacuum, the equivalent resistance of multipactor decreases when the Q factor of the system increases. For a system with a fixed Q factor, the equivalent resistance initially increases and then decreases, and the reactance initially decreases and then increases with rising pressure. The electron density shows insignificant variation and the ionization rate decreases while the pressure exceeds 5Torr. The phase between voltage and current dominates the plasma power. With consideration of metastable-state dynamics, the dominant ionization reaction shifts to penning ionization and step-wise ionization.