The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conv...The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.展开更多
Purpose Precise measurements of the cavity-loaded quality factor(Q_(L))are essential for monitoring the performance of superconducting radio frequency cavities.The conventional“field-decay method”cannot be used to m...Purpose Precise measurements of the cavity-loaded quality factor(Q_(L))are essential for monitoring the performance of superconducting radio frequency cavities.The conventional“field-decay method”cannot be used to measure Q_(L)accurately when the impedance is mismatched.Researchers at the China ADS Front End Demo Linac(CAFe)therefore introduced a new Q_(L)calibration algorithm for mismatched impedance conditions,which they validated through testing at the CAFe facility.The Test Stand 2(TS2)facility at the European Spallation Source(ESS),which is equipped with a high-power circulator having an adjustable reflection coefficient,provides increased experimental flexibility for validating the proposed CAFe algorithm.The present study further validates the proposed algorithm at the ESS TS2 facility.Methods In this study,we utilized the CAFe algorithm to measure Q_(L)at the ESS TS2 facility in the presence of mismatched impedance.The CAFe algorithm is a modified version of the“field-decay method,”which is based on the cavity differential equation.A more concise alternative derivation of the proposed CAFe algorithm is given in Appendix.The experimental setup at the TS2 facility enables the adjustment of the circulator bias current to vary the reflection coefficient,thereby introducing an impedance mismatch.Our primary focus here is to calibrate the actual values Q_(L)and the cavity detuning Q_(L)under these mismatch conditions.Results Our results reconfirm the effectiveness of the CAFe algorithm by accurately calibrating Q_(L)andΔf at the ESS TS2 facility,even when the impedance is mismatched.Our successful calibration of Q_(L)andΔf under mismatched conditions highlights the practicality and reliability of the CAFe proposed algorithm.When calibrating the cavity half bandwidth and detuning,the Lorentz force detuning and direct current offset may introduce uncertainties of approximately±5 Hz and±4 Hz,respectively.展开更多
基金supported by the project of Large Research Infrastructures"China initiative Accelerator-Driven System"(No.2017-000052-75-01-000590)"Studies of intelligent LLRF control algorithms for superconducting RF cavities"(No.E129851YR0)the National Natural Science Foundation of China(No.12205344).
文摘The accurate measurement of parameters such as the cavity-loaded quality factor(Q_(L))and half bandwidth(f_(0.5))is essential for monitoring the performance of superconducting radio-frequency cavities.However,the conventional"field decay method"employed to calibrate these values requires the cavity to satisfy a"zero-input"condition.This can be challenging when the source impedance is mismatched and produce nonzero forward signals(V_(f))that significantly affect the measurement accuracy.To address this limitation,we developed a modified version of the"field decay method"based on the cavity differential equation.The proposed approach enables the precise calibration of f_(0.5) even under mismatch conditions.We tested the proposed approach on the SRF cavities of the Chinese Accelerator-Driven System Front-End Demo Superconducting Linac and compared the results with those obtained from a network analyzer.The two sets of results were consistent,indicating the usefulness of the proposed approach.
基金supported by the project of Large Research Infrastructures“National Natural Science Foundation of China”(Grant No.U22A20261)the“Studies of intelligent LLRF control algorithms for superconducting RF cavities”(Grant No.E129851YR0)the“National Natural Science Foundation of China”(Grant No.12205344).
文摘Purpose Precise measurements of the cavity-loaded quality factor(Q_(L))are essential for monitoring the performance of superconducting radio frequency cavities.The conventional“field-decay method”cannot be used to measure Q_(L)accurately when the impedance is mismatched.Researchers at the China ADS Front End Demo Linac(CAFe)therefore introduced a new Q_(L)calibration algorithm for mismatched impedance conditions,which they validated through testing at the CAFe facility.The Test Stand 2(TS2)facility at the European Spallation Source(ESS),which is equipped with a high-power circulator having an adjustable reflection coefficient,provides increased experimental flexibility for validating the proposed CAFe algorithm.The present study further validates the proposed algorithm at the ESS TS2 facility.Methods In this study,we utilized the CAFe algorithm to measure Q_(L)at the ESS TS2 facility in the presence of mismatched impedance.The CAFe algorithm is a modified version of the“field-decay method,”which is based on the cavity differential equation.A more concise alternative derivation of the proposed CAFe algorithm is given in Appendix.The experimental setup at the TS2 facility enables the adjustment of the circulator bias current to vary the reflection coefficient,thereby introducing an impedance mismatch.Our primary focus here is to calibrate the actual values Q_(L)and the cavity detuning Q_(L)under these mismatch conditions.Results Our results reconfirm the effectiveness of the CAFe algorithm by accurately calibrating Q_(L)andΔf at the ESS TS2 facility,even when the impedance is mismatched.Our successful calibration of Q_(L)andΔf under mismatched conditions highlights the practicality and reliability of the CAFe proposed algorithm.When calibrating the cavity half bandwidth and detuning,the Lorentz force detuning and direct current offset may introduce uncertainties of approximately±5 Hz and±4 Hz,respectively.
