Abstract
Input couplers for radio-frequency accelerating cavities with heavy beam loading undergo many multipactoring zones due to the wide range of input powers. Furthermore, regular coaxial lines have more multipactoring than rectangular waveguides because of more uniformity of the electromagnetic field. Grooving conductor surfaces of coaxial lines is expected to be a promising method for suppressing multipactoring under any conditions with heavy beam loading. In this paper, we present a method for designing practical fine grooves on conductor surfaces of coaxial lines to suppress multipactoring, based on multipactoring zone maps, and demonstrate the suppressive power both in high-power tests and accelerator operations.
Highlights
INTRODUCTIONRadio-frequency (rf) input couplers (couplers) are one of the most important components in high-power rf systems
Radio-frequency input couplers are one of the most important components in high-power rf systems
The couplers for the ARES have been tested in a test stand for time-averaged powers of the continuous wave (CW) of up to and over 800 kW [14,15]
Summary
Radio-frequency (rf) input couplers (couplers) are one of the most important components in high-power rf systems. There was no conditioning effect and no improvement in one of the two cavities even after the couplers had been replaced by new ones which had passed high-power tests without exhibiting multipactoring symptoms and the inner surfaces of the coupler ports had been scraped and wiped to remove the possibility of multipactoring sources in the cavities. From a point of view that multipactoring-free couplers should be developed toward a higher luminosity B-factory, where the vacuum pressures in the ARES cavities will be higher due to the higher beam currents, we have made a decision not to replace CavityM, but rather to use it as a test stand at the KEKB accelerator. We have demonstrated the performance of couplers with fine grooves (grooved couplers) in a test stand and in KEKB operations
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