1.Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
2.School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
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Feng Qiu, Yuan He, An-Dong Wu, et al. In situ mitigation strategies for field emission-induced cavity faults using low-level radiofrequency system. [J]. Nuclear Science and Techniques 33(11):140(2022)
Feng Qiu, Yuan He, An-Dong Wu, et al. In situ mitigation strategies for field emission-induced cavity faults using low-level radiofrequency system. [J]. Nuclear Science and Techniques 33(11):140(2022) DOI： 10.1007/s41365-022-01125-8.
In the Chinese ADS front-end demo superconducting radiofrequency linac (CAFe) at the Institute of Modern Physics, a burst-noise signal-triggered cavity fault frequently appears during beam commissioning. These events are characterized by a rapid burst noise in the cavity pick-up, which may lead to an unexpected low-level radiofrequency (LLRF) response that eventually causes a cavity fault. To eliminate the undesirable reaction of the LLRF control loop, we propose a method that uses a burst-noise detection and processing algorithm integrated into the LLRF feedback controller. This algorithm can prevent undesired regulations in LLRF systems. Data analysis revealed that some burst-noise events did not exhibit measurable energy loss. In contrast, the other events were accompanied by a rapid loss of cavity stored energy and exhibited similarities to the "E-quench" phenomena reported in other laboratories. A particle-in-cell simulation indicated that the suspected E-quench phenomenon may be related to a plasma formation process inside the cavity. Fortunately, the LLRF algorithm is robust to the two different types of burst-noise events and can significantly mitigate the corresponding cavity faults in CAFe beam commissioning.
Field emissionFlashoverE-quenchSuperconductingLLRFCAFePlasma formation
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