论文标题
永久磁铁系统的简单改进，用于千里平衡：几乎没有成本的更平坦的场
A Simple Improvement for Permanent Magnet Systems for Kibble Balances: More Flat Field at Almost No Cost
论文作者
论文摘要
永久性磁铁与烤肉一起将磁通量集中在圆柱形气隙中，被广泛用于千里平衡。这些实验需要沿垂直路径的均匀磁通量密度，通常是气隙长度的很大一部分。在气隙两端存在的条纹字段限制了磁通密度变化不超过某个相对分数的区域（此处：$ 5 \ times 10^{ - 4} $）在磁铁系统中心的通量密度。通过简单地将带有矩形横截面的铁环添加到气隙的每一端的内轭上，可以抵消边缘场的效果，因此，增加了磁通密度在给定的公差频带内的区域的长度。与替代方案相比，使用较高的磁铁，该提出的方法产生的磁铁系统具有均匀场的扩展区域，而不会显着增加磁铁系统的质量。潜在的应用包括紧凑和桌上的千里平衡。我们研究了由其他环引起的磁系统性能的不利影响：磁场强度，线圈 - 电流效应以及径向场对田间径向位置的依赖性。没有发现实质性的劣势。取而代之的是，此处介绍的方法优于先前建议的方法来改善径向场的径向依赖性，例如较短的外轭。总而言之，在内部轭中添加环可提高磁场的均匀性，而不会对磁铁系统的功能，成本和外形效果不利。
Permanent magnets together with yokes to concentrate the magnetic flux into a cylindrical air-gap are widely employed in Kibble balances. These experiments require a uniform magnetic flux density along a vertical path, typically a substantial fraction of the length of the air-gap. Fringe fields that are present at both ends of the air-gap limit the region where the flux density does not change more than a certain relative fraction (here: $5\times 10^{-4}$) of the flux density in the center of the magnet system. By simply adding an iron ring with a rectangular cross-section to the inner yoke at each end of the air gap, the effects of the fringe fields can be counteracted, and, hence, the length of the region, where the flux density remains within a given tolerance band is increased. Compared to the alternative, employing a taller magnet, the proposed method yields a magnet system with an extended region of a uniform field without significantly increasing the mass of the magnet system. Potential applications include compact and table-top Kibble balances. We investigate possible adverse effects on the performance of the magnet system caused by the additional rings: magnetic field strength, coil-current effect, and a dependence of the radial field on the radial position in the field. No substantial disadvantage was found. Instead, the method presented here outperformed previously suggested methods to improve the radial dependence of the radial field, e.g., shorter outer yoke. In summary, adding rings to the inner yoke improves the uniformity of the field without a detrimental effect to function, cost, and form factor of the magnet system.
