Search

High energy FRagment Separator (HFRS), a full superconducting beam line, consists of 11 dipoles and 13 multiplets with the magnetic rigidity of 25 Tm and the large acceptance of ±165 mm. The multiplet contains three magnets nested with octupole, sextupole, quadrupole or steering dipoles, which are arranged together in a common cryostat. A Coil-dominated multipole magnets based on Discrete-Cosine-Theta (DCT) geometry is presented, which is expected to reduce the cold mass and shorten the length of beam line. A total of 200 G10 mandrels with a diameter greater than 400 mm are required and machined with grooves to hold the 6-around-1 cable securely. In order to minimize the costs and periods of magnets manufacture, injection molding is proposed and capable of mass-producing the formers. The first full-size prototype named L800 (effective length = 800 mm) has been successfully tested. Since the measured integral harmonics of the L800 exceed 10 units (only b3n component for 2n-pole field), the optimization of magnetic design is carried out to minimize the undesired harmonics. This paper will present the latest of the design and development process of the HFRS multipole magnets.

The superferric superconducting dipoles are designed for the High energy FRagment Separator (HFRS) of the Heavy-ion Accelerator Facility (HIAF) in China. The dipole magnets of the separator will have a deflection radius of 15.7 m, a field up to 1.6 T with a ±160 mm × ±62 mm good field region and an effective length of 2.74 meters. In the HIAF-HFRS, there will be a total of 11 superferric dipoles under construction. The dipole consists of two superconducting coils, a coil casing, a cryostat, and a warm iron yoke. The superconducting coils are protected by the scheme of quench detection and energy-extraction. At present, the first prototype dipole has been fabricated and tested, which reaches the design current of 210 A without a quench and the magnetic field of 1.64 T at the good field area, meeting the physical requirements. The measured results of magnetic field and energy discharge behaviors are in good agreement with the calculations. This paper describes the details of mechanical design, construction and the testing results of the prototype.

A superconducting fast cycling dipole prototype with a central field of 6 T and ramp rate of 1 T/s for ion synchrotron is currently under development at Institute of Modern Physics (IMP). The magnet utilizes a modified cos θ coil design, employing multi-strand round cable in formed grooves. The ribs of straight section of the coil formers have been removed to improve the excitation efficiency. Low loss round cables, made from NbTi/CuMn superconducting wires with a filament of 4.1 um, and the G10 formers are used to reduce AC losses during the ramping operation. The copper cold conduction strips are arranged between layers to improve the cooling efficiency. Bladder and key technology is adopted to prestress the coils. 2D layout of the coil is obtained through a linear programming code. This paper presents the round cable design, 2D cross section optimization, coil end and mechanical design, thermal analysis of the magnet, as well as the development of a technical prototype.

Fe-based nanocrystalline materials is a typical soft-magnetic material with advantages such as high saturated magnetic flux, high resistivity and low magnetostriction coefficient. By utilizing a specialized winding process, the ultra-thin strip has been successfully applied for use in scanning magnetic cores. For static field, the simulated and tested integral magnetic field uniformity is consistent, and tested effective length is slightly shorter than simulated one. The static magnetic field can meet the needs of scanning magnets. For transient field, the new iron core has less magnetic field delay and distortion compared to silicon steel sheet iron. The simulated maximum magnetic field delay is reduced from 161 Gauss to 16 Gauss. The maximum magnetic field delay of silicon steel sheet iron under test is 87 Gauss, and the corresponding data of the new iron core is almost 0 Gauss. With the weakening of the magnetic field delay, the magnetic field distortion should also be suppressed. With the novel iron core, the magnetic field of the scanning magnet can be improved, thereby reducing the distance from the scanning magnet to the terminal. Rotating gantry is the focus of current research on proton and heavy ion therapy accelerator facilities. This novel iron core can facilitate a decrease in the rotating diameter and weight of the gantry, while enhancing the scanning accuracy. Moreover, the novel iron core can be exploited in scenarios where ferrite cores are “excess capacity”, but traditional silicon steel cores are “insufficient capacity”, such as for certain bump magnets used in synchrotrons.

In this paper, a curved dipole magnet with Discrete-Cosine-Theta (DCT) coils which have compact ends and higher excitation efficiency, used for carbon ion therapy treatment facility is discussed. The dipole magnet has a bending angle of 90 degrees and a bending radius of 0.8 m. The magnet is ramped from 0 T to 2.9 T with a maximum rate of 1 T/s. However, the ramping magnetic field induces eddy current loss in metallic structure and ac loss in superconductor, resulting in temperature rise, and even quenching of the magnet. Therefore, a deep understanding of these effects is crucial for the design process. To mitigate the overall coil loss, reasonable structural design and conductor specifications are implemented. Furthermore, through finite-element analysis, the temperature distribution of the magnet under different cooling methods, such as LHe (Liquid Helium) bath and thermal conduction, are calculated in detail. Multiple reasonable cooling structures are also designed to ensure the safety of the magnet.

The Space Environment Simulation and Research Infrastructure (SESRI), located at the Harbin Institute of Technology (HIT) in China, is a new infrastructure project proposed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS), and completed in 2022. As a critical part of SESRI, the compact synchrotron was designed with a circumference of less than 44 m and compact magnets. In order to achieve compact injection and improve injection efficiency, four fast-ramping bump magnets based on ferrite yokes were used. All four bump magnets have a fast falling time from 20–100 µs, a maximum magnetic field of 0.0797 T, and a gap of 60 mm. To reduce the magnetic eddy current effect and coil inductance during fast excitation, ferrite core structures with single copper bar saddle windings are used. Further, window-frame structures are used to facilitate the ferrite-core machining process. After the prototype bump magnet was fabricated and the pulsed magnetic field measured, it was found that the integrated magnetic field curve did not align with the output current curve of the power supply. This was found to be caused by eddy currents from the copper gaskets between ferrite cores. Through the simulation and secondary testing of the gasket-induced eddy currents using different materials, the eddy current has been significantly reduced. In this study, the magnetic field optimization, structural design, eddy current calculation, and magnetic field measurement of the fast-ramping bump magnets are analyzed.

As one of the key components of synchrotron injection and extraction system, the coil of the septum is subjected to large electromagnetic force during excitation, resulting in inevitable deformation of the coil, which affects the safe and stable operation of the magnet. Therefore, it is necessary to conduct a detailed analysis of the failure mechanism of the coil during operation. In this paper, an improved septum magnet structure is proposed, which reduced the stress of the coil effectively. Furthermore, a refined model of the septum magnet is established based on finite element method, the electromagnetic field and deformation of the magnet under the operating state are simulated, more fine strain/stress profiles of the copper wire, insulation and epoxy have been obtained. And compared with the traditional homogenized model and measurement results, the results show that the refined model can reflect the mechanical response between the turns of the coils more effectively. According to the results, a septum magnet is developed, which effectively improves and extends the operating stability and service life than previous septum magnet.

The dynamic quench behavior is investigated for a superconducting dipole magnet wound with the six-round-one superconducting cables (six NbTi/Cu wires and one center copper wire), which is protected by a recently developed protection scheme based on the quench-back effect triggered by the center copper wire automatically. The quench transients were measured based on the real-time data acquisition system and also calculated by our previously developed quench model. During the energy discharge of the magnet, the featuring points can be observed on the evolution curves of coil current, induced current, and voltage, which indicates the occurrence of a quench-back. By comparing the results for the cases with and without quench-back effect, the role of the quench-back on the quench protection is analyzed further. Meanwhile, the adjustable resistor can be utilized to control the quench-back effect to satisfy the quench protection requirements.