Compact muon solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN large hadron collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in theCMSdetector, including the large ferromagnetic parts of the yoke, is required. To measure the field in and around ferromagnetic parts, a set of flux-loops and Hall probe sensors will be installed on several of the steel pieces. Fast discharges of the solenoid during system commissioning tests will be used to induce voltages in the flux-loops that can be integrated to measure the flux in the steel at full excitation of the solenoid. The Hall sensors will give supplementary information on the axial magnetic field and permit estimation of the remanent field in the steel after the fast discharge. An experimental R&D program has been undertaken, using a test flux-loop, two Hall sensors, and sample disks made from the same construction steel used for the CMS magnet yoke. A sample disc, assembled with the test flux-loop and the Hall sensors, was inserted between the pole tips of a dipole electromagnet equipped with a computer-controlled power supply to measure the excitation of the steel from full saturation to zero field. The results of the measurements are presented and discussed.
The CMS Magnetic Field Measuring and Monitoring Systems
本文介绍了紧凑型μ子螺线管（CMS）探测器的磁场测量和监测系统的性能。为了交叉检查用CMS磁体模型获得的磁通量分布，使用了四个用于测量检测器体积中的磁通量密度的系统。测量了6米直径超导螺线管内的磁感应强度，目前由四个核磁共振（NMR）探头监测，探头安装在桶形强子量能器外，使用特殊的管子。另外两个NRM探头安装在跟踪系统的表面。2006年，使用10个基于霍尔效应的三维（3D）B传感器，在直径为3.448 m，长度为7 m的圆柱体中精确测量了超导螺线管内部的磁场。这些B传感器安装在自动化现场测绘机的两个螺旋桨臂上。除了这些测量系统之外，还开发了一种用于在CMS检测器操作期间监测磁场的系统。在水平平面中的螺线管内部，4个3D B传感器安装在跟踪检测器的面上。12个三维B传感器安装在磁通返回轭鼻盘的表面上。在CMS磁轭的气隙中安装了70个3D B传感器。专门开发的磁通回路技术用于CMS磁轭钢块内部最复杂的磁通量密度测量。磁通回路安装在磁通返回轭块的22个部分中。这些线圈包围的面积在桶形轮块中为0.3至1.59 m $^{2}$，在轭端盖盘块中为0.5至1.12 m $^{2}$。这些系统的发展和跨CMS磁体的磁通量密度测量的结果在这篇评论文章中介绍和讨论。
