Analysis of modules failure in solid-state amplifier for high current RFQ

The new RF system of Radio Frequency Quadrupole (RFQ) accelerator in ADS project at the Institute of Modern Physics (IMP) was upgraded in the beginning of 2017, the original tetrode amplifier was replaced by two new unconditionally stable solid-state amplifiers (SSAs) for proton acceleration, which have the same 80 kW nominal power and combine at least 120 kW inside the cavity with two uniform couplers. In the SSAs, the multiple power modules were amplitude-modulated and phase-optimized for power combination, but one or a couple of damaged circulators (including sink loads) might cause failure of the whole RF system. Especially, according to experiments and simulation, when the transmission line between the two different level combiners met a specific condition, the scattering parameter of the system would have great fluctuations, even cut-off, if damages occurred in circulators or sink loads. In this paper, the simulation methods for multi-level synthetic amplifying are introduced in detail; as a new design concept of the amplifier, the failure analysis and related experiments focusing on amplification links of SSA under special circumstances are also presented.