Simulation of ion noise character in klystron

Characteristics of ion noise in a klystron was discussed by using a hybrid model. One-dimensional particle-in-Cell method (PIC) simulation code is developed and the relation between ion noise and phase distortion was obtained. The characteristics of the ion noise in a klystron are treated as an example to be analyzed by this PIC code and the diagnosis of ion current on cathode was made. The numerical simulation results accord with measured values very well. When the beam current increases, the ion noise amplitude will decrease and become stable. There exists on optimal value of magnetic focusing field and beam voltage, which can minimize the ion noise amplitude.