Helical resonator with modulated radius for improved multipactor threshold: Numerical and experimental results

This contribution presents numerical and experimental results on a 2
^nd
order UHF filter prototype that exploits helical resonators with modulated radius. Earlier works have proposed this geometry as means to enhance power handling without significantly compromising on unloaded quality factors. Here we present a detailed prototype design and evaluate its performance at low and high power levels using both rigorous numerical tools as well as the results of an experimental test campaign. Low power results include CST predictions against measurements on a Vector Network Analyser. High power results include predictions from the tool SPARK3D as well as the outcome of a test campaign at the ESA-VSC laboratories. Despite some discrepancies in the power handling predictions, which are largely attributed to uncertainties associated with prototyping, the presented results indicate that there is margin for significant performance improvement by adopting the large gap approach for this class of filters.