Ultrawideband, high-power, microstripline test setup for experimental study and characterization of multipactor.

This paper discusses different components of a high-power test setup for replicating multipactor in a laboratory environment. We developed a broadband test cell for parallel-plate multipactor discharges that can operate from DC to 1.2 GHz. The proposed test cell design features a multi-step transition from a coaxial line to a microstripline with negligible insertion loss suitable for high-power breakdown experiments. The multipactor section is adjustable and replaceable, offering flexibility in conducting various multipactor tests, such as different gap distances and local surface treatments. We incorporated two local multipactor detection methods, an electron multiplier tube and a biased standalone probe to rapidly and reliably detect the growth of secondary electrons in the multipactor vicinity. The driving circuits of these detection methods have been designed to filter out RF coupling while preserving the detection signal due to multipactor current. To demonstrate the accuracy of the proposed test setup, we validated the multipactor thresholds determined in simulation using the 3D particle-in-cell module of CST Microwave Studio. We obtained very good agreement between simulation and experimental results over the broadband frequency range. The topics discussed in this paper further inform how to address the design obstacles encountered in developing a bench-top multipactor test setup.