Analysis of the over-loaded reflection of solid state power amplifier module

Background C-ADS (Chinese Accelerator Driven Sub-critical System) injector II superconducting linac uses solid state amplifier (SSA) to drive normal temperature acceleration structure and superconducting cavity. During operation, some power amplifier modules of SSA were damaged due to overload of reflected power. [Purpose] This study aims to analyze the reasons that caused over loading of SSA. [Methods] The relationship between the distribution of reflected power among the amplifier modules, the S parameters of power combination network, and various output states of amplifier module is derived and analyzed. [Results] The results showed that the failure of amplifier module would cause the unbalanced of reflected power distribution among modules. Some modules would undertake the reflection above normal level. [Conclusions] For the SSA with one-stage combined net, only failure module probably undertakes over loading reflected power; for the SSA of the multi-stage combined net, any module in the combined branch where the faulty module was located may have an overload reflection. (authors)