Qinggao Yao

Magnetic Field Design of the Dipole for Super-FRS at FAIR

The Super-FRS (Super FRagment Separator) is a part of FAIR (Facility for Antiproton and Ion Research), which will be constructed at GSI, Germany by 17 countries. The Super-FRS comprises 24 superferric dipole magnets. The 2D and 3D magnetic field simulations of the prototype magnet are described in this paper. A passive trim slot and four chamfered removable poles are used to satisfy the required field homogeneity which is better than at 1.6 T, 0.8 T and 0.16 T in a wide elliptical useable aperture of 380 mm 140 mm. Measurement results at various field levels are shown in this paper as well. It can be seen from the comparison of calculation and measurement results that the magnetic designs of the magnet fulfils the requirements.

Design of a 7 T Superconducting Magnet for Lanzhou Penning Trap

A penning trap system called LPT (LANZHOU PENNING TRAP) is now being developed for precise mass measurements in IMP (Institute of Modern Physics). The most key component of LPT is a superconducting magnet. A 156 mm warm bore and two cylinder good field regions with a distance of 220 mm are required for trapping ions and measurements. As the required homogeneity is better than 0.5 ppm, several complicated coaxial coils are used to produce such a magnetic field. The size and position of these coils are optimized by using a method combining linear program with multiobjective optimization. Superconducting shim coils and passive shim pieces are used to eliminate inevitable winding tolerances and environmental influence. The fringe field is decreased to 5 Gs at 2 m line from the center of the magnet by active shielding coils. The designs of the mechanical structure, the quench protection system are also introduced in this paper.

The Cold Test of Super-FRS Superconducting Dipole Prototype for FAIR Project

Superconducting dipole prototype of the Super-FRS (Super FRagment Separator) for FAIR Project (Facility for antiproton and Ion Research) which is jointly developed by the Institute of Modern Physics (Lanzhou), the Institute of Plasma Physics (Hefei) and the Institute of Electrical Engineering (Beijing), have passed the final magnetic field measurement and low temperature test. The magnetic flux density is up to 1.6 T when the operating current is 232 A, and magnetic field homogeneity meets the calculation result which is ±1 × 10-4. The single ramping tests up to 232 A and 278 A at the rate of 3 A/s, 3 triangular cycles ramping up to 232 A within 120 seconds, and the quench tests at 232 A and 278 A by using the spot heater were done. Some other tests were finished at the same time. All the test results indicate that the superconducting dipole prototype could meet the requirements of FAIR.

A 3 Tesla Superconducting Magnet for Hall Sensor Calibration

A 3 T superconducting magnet with a 70 mm diameter warm bore and energy storage of 47 kJ has been successfully fabricated and tested, which can be used to calibrate Hall sensors in high magnetic field as well as conduct superconducting experiments. The magnet consists of three solenoid coils and an iron yoke. The homogeneity of the magnetic field in the region of interest (ROI) is . The coils of the magnet were fabricated with NbTi-Cu superconducting wire and the stray magnetic field is shielded by an iron yoke. The coils and yoke are fully immersed in a helium vessel. The optimized structural design, stress and quench simulation, fabrication and test results are presented in this paper.

Magnetic Field Measurement for Synchrotron Dipole Magnets of Heavy-Ion Therapy Facility in Lanzhou

Magnetic field measurement system is an indispensable part of Heavy-Ion Therapy Facility in Lanzhou (HITFiL). The Hall probe mapping system and long coil integral measure system are developed for dipole magnets measurement. The main parameters and the structure of the systems are described. Magnetic field calculations and the design of the synchrotron dipole magnets are also presented in brief. The main measurement results of magnetic field are shown in the article which includes excitation curve, transverse field homogeneity, effective length and integral field homogeneity. The test results prove that the measurement system is fully competent for the demand of HITFiL project, and ensure the smooth operations of subsequent measurement.

Some Superconducting Magnets at IMP

Some superconducting magnets research at IMP (Institute of Modern Physics, CAS, Lanzhou) will be described in this paper. Firstly, a superconducting electron cyclotron resonance ion source (SECRAL) was successfully built to produce intense beams of highly charged heavy ions for Heavy Ion Research Facility in Lanzhou (HIRFL). An innovation design of SECRAL is that the three axial solenoid coils are located inside of a sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. For 28 GHz operation, the magnet assembly can produce peak mirror fields on axis of 3.6 T at injection, 2.2 T at extraction, and a radial sextupole field of 2.0 T at plasma chamber wall. Some excellent results of ion beam intensity have been produced and SECRAL has been put into operation to provide highly charged ion beams for HIRFL since May 2007. Secondly, a super-ferric dipole prototype of FAIR Super-FRS is being built by FCG (FAIR China Group) in cooperation with GSI. Its superconducting coils and cryostat is made and tested in the Institute of Plasma Physics (IPP, Hefei), and it more 50 tons laminated yoke was made in IMP. This super-ferric dipole static magnetic field was measured in IMP, it reach to the design requirement, ramping field and other tests will be done in the future. Thirdly, a 3 T superconducting homogenous magnetic field solenoid with a ¿70 mm warm bore has been developed to calibrate Hall sensor, some testing results is reported. And a penning trap system called LPT (Lanzhou Penning Trap) is now being developed for precise mass measurements.

Quench Protection Design and Simulation of a 7 Tesla Superconducting Magnet

A 7 Tesla superconducting magnet with a clear warm bore of 156 mm in diameter has been developed for Lanzhou Penning Trap at the Institute of Modern Physics for high precision mass measurement. The magnet is comprised of 9 solenoid coils and operates in persistent mode with a total energy of 2.3 MJ. Due to the considerable amount of energy stored during persistent mode operation, the quench protection system is very important when designing and operating the magnet. A passive protection system based on a subdivided scheme is adopted to protect the superconducting magnet from damage caused by quenching. Cold diodes and resistors are put across the subdivision to reduce both the voltage and temperature hot spots. Computational simulations have been carried in Opera-quench. The designed quench protection circuit and the finite element method model for quench simulations are described; the time changing of temperature, voltage and current decay during the quench process is also analysed.

The Main Dipole Magnets Design and Test of HIMM Project

In the project of Heavy Ion Medical Machine, there are eight dipole magnets in the synchrotron and ten dipole magnets in the high-energy beam line used for beam bending. Both types of dipole magnets have the same bending radius and bending angle, but the gaps are different. The maximum magnetic field of synchrotron dipole is 1.66 T, and the high beam line dipole is 1.6 T. The magnetic field calculation and the structure design are presented in this paper; the trim slot in the pole and the removable pole ends are used in order to reach the required field homogeneity. The magnetic field measurement results, which include field homogeneity and reproducibility, are also shown in details. The test results show that the dipole magnet design could satisfy the major specified physical requirements.

Preliminary Design of Superconducting Dipole Coils for HIAF in IMP

Heavy-Ion Advanced Research Facility (HIAF) is a project in the twelfth five-year plan for heavy ion research in China. The dipole magnet system of the low energy beam line on this project plans to use superconducting magnets. This type of magnet is similar to the prototype dipole for Super-FRS of FAIR, and its features are warm iron and warm bore, only the coils are housed in one cryostat and cooled with liquid helium. The coils have a trapezoidal-shaped configuration which will be wound with NbTi wires of high Cu/Sc ratio. This paper introduces the preliminary design of the superconducting coil system which including the stability analysis of the superconductor, selection of the superconducting wire, quench analysis, mechanical structure analysis of coils and coil box based on 3D finite-element analysis. According to the results of the analysis, more details of quench protection and structure should be taken into account in future research.

The Magnetic Field Design of HITFiL Cyclotron

A new Project named HITFiL (Heavy Ion Tumors Therapy Facility in Lanzhou) is being constructed. Its initial injector is a compact cyclotron, which provides a 7 Mev/10 uA carbon beam for the synchrotron. This paper introduces an effective method to design the isochronous magnetic field of the cyclotron. Using a 3D finite element code, an iterative shimming process has been accomplished successfully. The results show that the isochronous deviations between calculated values and theory are smaller than 5 Gauss at most radii and therefore fulfill the requirements. In addition, the magnetic design of the extraction magnets and their interaction with the main field will be presented in this paper.