Parasitic modes suppression in CW cold tests of 1.3 GHz 9-cell high Q cavities at IHEP

TL;DR

This paper discusses the suppression of parasitic modes in continuous wave cold tests of 1.3 GHz 9-cell high-Q superconducting cavities at IHEP, improving measurement accuracy and cavity performance.

Contribution

It presents a method to completely suppress parasitic modes during CW cold testing of high-Q cavities, ensuring more accurate cavity characterization.

Findings

Parasitic modes were successfully suppressed in CW tests.

Mid-temperature bake improved cavity quality factor.

Enhanced testing system guaranteed measurement accuracy.

Abstract

The CW RF test of 1.3 GHz 9-cell cavity in liquid helium bath at 2 K is a very important key point in the cavity procurement. Some problems can be found through the test, according which to optimized and improve the process of cavity. Recently, Medium temperature (mid-T) furnace bake of 1.3 GHz 9-cell cavities have been carried out at IHEP. Through the proceed of mid-T bake, the quality factor of cavity has been greatly improved. While the excitation of the parasitic modes in the high Q cavities CW cold test has been encountered, which implies an error source for the cavity gradient and quality factor determination. In order to ensure the testing accuracy of superconducting cavity, we have improved the testing system. Finally, the parasitic mode is completely suppressed and the CW RF cold test of high Q cavity is guaranteed.