Analysis of plasma impedance in the Linac4 negative hydrogen ion source

Linac4 is radio frequency (RF) driven type negative hydrogen H− ion source. In the RF system, it is required to match the impedance between the RF-system and plasma loading. In order to match the impedance, it is essential to analyze the plasma impedance. In this study, we analyze the plasma impedance by using the Electro-Magnetic Particle in Cell model. As a result, plasma impedance calculated by the Electro-Magnetic Particle in Cell model agrees qualitatively with one calculated by fluid model model in the steady state. On the other hand, plasma impedance calculated by the numerical simulation code is significantly different from one calculated by the zero dimensional equivalent circuit model during plasma ignition. The results show that the kinetic effects are necessary especially during plasma ignition. It is useful to propose more efficiency power transfer.