发表机构
Thomas Jefferson National Accelerator Facility; CERN; Old Dominion University（托马斯·杰斐逊国家加速器设施; 欧洲核子研究组织; 老道明尼大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究优化了杰斐逊实验室的四极谐振器（QPR）系统，实现了多频率SRF材料表征，验证了其测量性能并量化了不确定度，为SRF材料表征提供了可靠平台。
AI 中文摘要
四极谐振器（QPR）提供了一个基于样品的平台，可在受控的场、频率和温度条件下表征用于超导射频（SRF）应用的材料。本文介绍了杰斐逊实验室（JLab）QPR系统的设计优化、调试与验证，包括对测量不确定度的定量评估。谐振器几何结构从CERN的Version-II设计重新优化，以改善四极模式分离，实现在400、806、1221和1640 MHz下的四个可用模式。测量系统结合自激回路RF运行、电缆损耗校正的功率校准、基于衰减的外部Q校准，以及RF-DC热替代量热法，以确定峰值表面磁场Bpk和样品表面电阻Rs。对块状Nb和Nb3Sn-Ta-Cu样品的调试测量验证了系统在宽频率、温度和RF场范围内的响应。提取的超导能隙参数与已报道的Nb、Nb3Sn的值以及单单元腔测量获得的值一致。调试后的系统工作温度范围为1.8 K至接近样品的超导转变温度，可及的Bpk值范围约为5 mT至取决于样品和温度的加热器功率预算极限；在400 MHz和4 K下，块状Nb的最大演示场为60 mT。当r = PDC2/PDC1小于0.9时，Bpk的合成相对标准不确定度为8.3%，Rs的合成相对标准不确定度低于18%。在95%置信水平下，Bpk的最坏情况分辨率约为1.35 mT，而在10 mT和2 K下，Rs的分辨率低于1 nOhm。这些结果确立了JLab QPR作为一个经过校准、多频率且具有量化测量不确定度的SRF材料表征平台的地位。
英文摘要
A quadrupole resonator (QPR) provides a sample-based platform for characterizing materials for superconducting radio-frequency (SRF) applications under controlled field, frequency, and temperature conditions. This paper presents the design optimization, commissioning, and validation of the Jefferson Lab QPR system, including a quantitative assessment of measurement uncertainty. The resonator geometry was re-optimized from the CERN version-II design to improve quadrupole-mode separation and enable four usable modes at 400, 806, 1221, and 1640 MHz. The measurement system combines self-excited-loop RF operation, cable-loss-corrected power calibration, decay-based external-Q calibration, and RF-DC thermal-substitution calorimetry to determine the peak surface magnetic field Bpk and sample surface resistance Rs. Commissioning measurements on bulk Nb and Nb3Sn-Ta-Cu samples validated the system response over a broad range of frequency, temperature, and RF field. The extracted superconducting energy-gap parameters are consistent with the reported values for Nb and Nb3Sn, as well as with those obtained from single-cell cavity measurements. The commissioned system operates from 1.8 K to near the superconducting transition temperature of the sample, with accessible Bpk values from approximately 5 mT to a sample- and temperature-dependent heater-power-budget limit; a maximum field of 60 mT was demonstrated for bulk Nb at 400 MHz and 4 K. The combined relative standard uncertainties are 8.3% for Bpk and below 18% for Rs when r = PDC2/PDC1 is less than 0.9. The worst-case Bpk resolution at the 95% confidence level is approximately 1.35 mT, while the Rs resolution is below 1 nOhm at 10 mT and 2 K. These results establish the JLab QPR as a calibrated, multi-frequency platform with quantified measurement uncertainty for SRF material characterization.
