Quench-Induced Degradation of the Quality Factor in Superconducting Resonators

Abstract

Quench of superconducting radio-frequency cavities frequently leads to the lowered quality factor Q 0 , which had been attributed to the additional trapped magnetic flux. Here we demonstrate that the origin of this magnetic flux is purely extrinsic to the cavity by showing no extra dissipation (unchanged Q 0 ) after quenching in zero magnetic field, which allows us to rule out intrinsic mechanisms of flux trapping such as generation of thermal currents or trapping of the rf field. We also show the clear relation of dissipation introduced by quenching to the orientation of the applied magnetic field and the possibility to fully recover the quality factor by requenching in the compensated field. We discover that for larger values of the ambient field, the Q-factor degradation may become irreversible by this technique, likely due to the outward flux migration beyond the normal zone opening during quench. Our findings are of special practical importance for accelerators based on low-and medium-β accelerating structures residing close to focusing magnets, as well as for all high-Q cavity-based accelerators.

Physics of Limiting Phenomena in Superconducting Microwave Resonators: Vortex Dissipation, Ultimate Quench and Quality Factor Degradation Mechanisms

“…In this chapter, the detailed physics behind the quality factor degradation due to quench in superconducting resonators is described [124]. The experimental evidence reported proves that the Q 0 degradation due to quench is a direct consequence after quench can be achieved when the cavity is quenched in the absence of the external magnetic field-an alternative to warming up above the critical temperature-is described along with a consistent physical model of this phenomenon.…”

“…The points refer to magnetic field B and potential U 0 chosen for the numerical solutions in (a) [124]. .…”

Перспективные Технологии Для Прикладных Резонансных Ускорителей Заряженных Частиц И Примеры Их Использования (Обзор)

“…Традиционные сверхпроводящие ускорители требуют наличия центральной криогенной системы для получения и распределения жидкого гелия, или же его постоянную доставку. Кроме того, содержание и обслуживание этих систем требуют особой квалификации и внимания персонала, поскольку при такой нештатной ситуации как квенч [323], размораживание или механическое повреждение, сверхпроводящий ускоритель или его часть может навсегда выйти из строя [324,325]. Развитие технологий в области сверхпроводимости, произошедшее за последнее десятилетие, позволяют значительно упростить дизайн сверхпроводящих ускорителей, а также сделать их мобильными, энергетически и экономически эффективными при мощности пучка порядка 1 MW [326], чего невозможно достичь с помощью нормальнопроводящих установок.…”

Superradiance by ferroelectrics in cavity resonators

“…To derive an equation for the resonator feedback field, it is possible to follow the general methods for treating cavity resonators [59,60]. Here we keep in mind a cylindrical resonator cavity of radius R, length L, and volume V res = πR 2 L. The axis of the resonator is along the axis x.…”