功率天平磁体系统设计综述

Review on the design of the Kibble balance magnet system

在新国际单位制下,功率天平是复现质量单位千克最重要的实验装置之一。功率天平实验装置的核心部件是提供测量磁场的磁体系统,它在线圈位置处产生的磁通密度沿线圈导线积分形成磁几何因子,构建出电磁功率与机械功率之间的等价关系,继而可确定被测质量的量值。因此,磁体系统产生磁场的性能,对千克量值复现的准确性具有重要影响。文章梳理了功率天平磁体系统对千克复现准确性的影响,盘点了多种功率天平磁体系统设计的特点,分析和评估了不同磁体设计方案的性能。比较发现,以BIPM型磁体系统为代表的基于磁轭的径向磁体系统,在产生磁场的效率、磁屏蔽性能和设计对称性等方面均具有优势,是目前性能最优的功率天平磁体系统之一。

In the new international system of units,the Kibble balance is one of the most important experimental devices for realization of the mass unit,kilogram.The core element of the Kibble balance experiment device is the magnet system that provides the magnetic field measurement.The magnetic flux density generated at the position of the coil is integrated along the coil wire to form the magnetic geometry factor,and the equivalent relationship between the electromagnetic power and the mechanical power is constructed,and then the measured mass can be determined.Therefore,the performance of the magnetic field generated by the Kibble magnet system significantly affects the final mass measurement accuracy.This paper analyzes how the magnet system affects the Kibble balance uncertainty and reviews the performance of various Kibble balance magnet systems.The comparison of different magnet systems is analyzed and evaluated.It shows that the radial magnet system based on magnetic yoke,represented by BIPM magnet design,has merits in efficiency of magnetic field generation,magnetic shielding and geometrical symmetry,which can be considered as one of the best Kibble balance magnet designs.