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A 230 MeV compact superconducting cyclotron CYCIAE-230 is being constructed by the China Institute of Atomic Energy, which can be used for proton therapy and space radiation physics research. The technology of magnetic field measurement, shimming and processing is the primary task to realize the isochronous acceleration of cyclotron. The CYCIAE-230 has high magnetic field, high field gradient and dense rotation orbits. Therefore, the isochronous field and tune diagram need to be amended simultaneously. The first harmonic is also shimmed at the same process to ensure a good extraction efficiency by using precessional extraction. The precision of field measurement, shimming and processing is much higher and the algorithm is much more difficult than those in normal temperature cyclotron. In addition, the compact structure of the magnet has very narrow installation space, which makes the design of the mapper more difficult. The process of main magnet construction includes strict control of room temperature and electromagnetic compatibility (EMC), precise measurement of magnetic field, comprehensive research of beam dynamics and multi-dimensional numerical control (NC) processing under the control of complex algorithms. In this paper, the magnetic field measurement, shimming and processing of the main magnet will be illustrated in detail.

A superconducting cyclotron named CYCIAE-230 is designed and under construction at the China Institute of Atomic Energy, Beijing, China, to provide a 230-MeV proton beam for cancer therapy. The cryogenic system has been completed and the machining of the magnet will be finished soon. The shimming procedure will be performed to obtain the final isochronous field, which requires the field measurement precision to be 5 × 10–5. A search-coil sensor based mapping system was developed to satisfy the measurement accuracy requirements, including a nuclear magnetic resonance probe to precisely measure the field at the cyclotron center and a moving search coil to obtain the field differences. Moreover, a Hall probe is integrated in the system to verify the field data. The system allows the probe motion and data acquisition to be performed automatically. In this paper, the field mapping requirements are listed, the design and calibration of the coil is described, and the field mapping system, including mechanical structure and control system, is presented in detail.

For the applications of proton therapy and proton irradiation, and based on the RD then, the construction progress and the B–H curve measurement results of the warm iron over the magnetic saturation region are outlined; the R&D of the superconducting coils system and the design of the field mapping system are also briefly introduced.

Started in January 2015, a 230-MeV superconducting cyclotron is under construction in the China Institute of Atomic Energy for proton therapy. A compact main magnet design with warm iron yokes and a superconducting coil system is adopted to reduce the size, construction, and operation cost of the cyclotron. In this paper, the field calculations of the main magnet are briefly described; then, the R&D of the superconducting coil system are outlined in detail, including the cryogenics design of the system, the forces, and stress analysis of the superconducting coil and support links, the power supply and quench protection design. Some preliminary test results are also presented.

The CYCIAE-100 Cyclotron is the main part of the BRIF project at China Institute of Atomic Energy. It is an isochronous compact cyclotron for the acceleration of H-, and it will provide proton beam of 75 MeV ~ 100 MeV with an intensity of 200 ?A ~ 500 ?A. The magnetic pole has the radius of 2000 mm and the magnetic gap is changing gradually from inner radius to outer radius. The maximum filed is 1.3 T and required average isochronous field accuracy is less than 10-4. The difficulties for the design of the magnetic filed measurements device is increased not only due to the field accuracy but also due to the very small space for the compact cyclotron compared with normal machine. This paper describes the field measuring system based on the Hall-probe that has been used for the mapping of field and provides the data for shimming of the cyclotron magnet. The azimuthal and radial position of hall probes will be obtained by optical encoder and linear grating, respective. The overall measurement was estimated to be in the range of ±0.01%.

The construction of a 100-MeV high-intensity cyclotron, from which proton beam will be extracted through stripping to several proton beam lines for different users, has been completed at China Institute of Atomic Energy. Given that it is the H-ions that are to be accelerated in the machine, the peak field is only 1.35 T. To simplify the fabrication, the pole adopts straight sector instead of the spiral one. Meanwhile, vertical focusing should be sufficiently high to obtain high-current proton beam. All these demands make it particularly difficult for the design and fabrication of the main magnet, which is heavy in weight and challenging to meet precision requirement in fabrication. In the process, we have developed a high-performance parallel computation PIC code for beam dynamics of high-current cyclotrons and for FFAGs, which can be used for beam dynamic simulation at a very precise level. The result is then applied to guide the design, fabrication, installation, magnetic mapping, and shimming of the 416-ton main magnet with a precision requirement up to 0.05 mm. Another challenge is due to the deformations of the magnet without/with the vacuum. The whole map measured in the vacuum has to be completed in such a big machine for the first time in the world. The result shows that all requirements, including the isochronous field, vertical focusing, and imperfection fields, have been satisfied properly. The first beam and the stable beam for an 8-h commissioning test had been achieved on July 4 and July 25, 2014, respectively.