Absolute instability in gyro-traveling-wave tube

Absolute instability is a major physics limitation in the realization of the ultimate capability of gyro-traveling-wave tube. The physical interpretations ,character and suppressing methods of absolute instability were analyzed and verified by a W-band TE01 experiment. A threshold current which brings about the transition to absolute instability was investigated. PIC results show that the occurrence of absolute instability is determined by the operating current. The interaction circuit with distributed loss is proved effective for stabilizing amplification by increasing the threshold current.