Phung K H, Romero J A, Roche T
TAE Technologies, Inc., Foothill Ranch, California 92610, USA.
Rev Sci Instrum. 2022 Nov 1;93(11):113553. doi: 10.1063/5.0101846.
The magnetic diagnostics across TAE Technologies' compact toroid fusion device include 28 internal and 45 external flux loops that measure poloidal flux and axial field strength, 64 three-axis (radial, toroidal, and axial) Mirnov probes, and 22 internal and external, axial-only Mirnov probes. Imperfect construction, installation, and physical constraints required a Bayesian approach for the calibration process to best account for errors in signals. These errors included flux loops not fitted to a perfect circle due to spatial constraints, Mirnov probes not perfectly aligned against their respective axes, and flux pickup that occurred within the insert (feedthrough) of the Mirnov probes. Our model-based calibration is derived from magnetostatic theory and the circuitry of the sensors. These models predicted outputs that were compared against experimental data. Using a simple least-squares optimization, we were able to predict flux loop data within 1% of relative error. For the Mirnov probes, we utilized Bayesian inference to determine three rotation angles and three amplifier gains. The results of this work not only gave our diagnostic measurements physical meaning, but also act as a safeguard to spot when instruments have malfunctioned, or when there is an error in database maintenance. This paper will go into the details of our calibration procedure, our Bayesian modeling, and the accuracy of our results compared to experimental data.
TAE技术公司紧凑型环形聚变装置的磁诊断设备包括28个内部和45个外部磁通环，用于测量极向磁通和轴向场强；64个三轴（径向、环向和轴向）米尔诺夫探头，以及22个内部和外部仅轴向的米尔诺夫探头。由于结构不完善、安装问题和物理限制，校准过程需要采用贝叶斯方法，以最好地考虑信号中的误差。这些误差包括由于空间限制，磁通环无法拟合为完美的圆形；米尔诺夫探头未完全与其各自的轴对齐；以及在米尔诺夫探头的插件（馈通）内发生的磁通拾取。我们基于模型的校准源自静磁理论和传感器的电路。这些模型预测的输出与实验数据进行了比较。通过简单的最小二乘法优化，我们能够在相对误差1%的范围内预测磁通环数据。对于米尔诺夫探头，我们利用贝叶斯推理来确定三个旋转角度和三个放大器增益。这项工作的结果不仅赋予了我们的诊断测量物理意义，还能在仪器出现故障或数据库维护存在错误时起到检测保障作用。本文将详细介绍我们的校准程序、贝叶斯建模以及与实验数据相比我们结果的准确性。
