中国工程物理研究院流体物理研究所目前正在建造一台医用11 MeV回旋加速器，该加速器磁铁采用小气隙、深谷结构以提供更高的平均磁场和更强的聚焦能力。为实现5×10-4的测量精度，自行研发了一套磁场点测装置，该装置可实现二维极坐标下的精确测量。经过多次磁场垫补，束流的相位偏移控制在±9°，一次谐波幅值控制在0.001 T以内，满足了磁铁的设计需求。在束流调试过程中，成功实现了质子束的引出，表明回旋加速器磁铁建造成功。此外，还对磁铁研制过程中出现的磁场缺陷及磁测误差进行了讨论。

An 11 MeV H－ compact cyclotron used for medical radioactive isotope production is under construction in Institute of Fluid Physics, CAEP. The cyclotron magnet adopts the design of small valley gaps and coulee structure which can provide high average magnetic field and strong focus ability. To achieve 5×10-4 measuring accuracy, a magnetic field mapping system has been developed. After iterative correction using field measurement data, the total phase excursion of the cyclotron is within ±9° and the first harmonic is less than 10-3 T, which are all acceptable. Furthermore, the beam testing declares the successful construction of the cyclotron magnet. Besides, some magnetic field influence factors were discussed, including the magnetic field distortion and measurement error.