Research On The Key Technology Of HIAF-BRing Fast Ramping Dipole Magnets

The higher beam intensity and energy are the continuous goals of heavy ion accelerator.The High-Intensity Heavy Ion Accelerator Facility（HIAF）,proposed by the Institute of Modern Physics,Chinese Academy of Sciences（IMP）,is being designed to provide primary and radioactive intense beams for nuclear and related research.The Booster Ring（BRing）is one of the key systems of HIAF,which is used to capture,accumulate,accelerate and extract the heavy ion beam injected by i Linac.Dynamic vacuum and space charge effects are key factors that limit the further increase of beam intensity.To obtain the high intensity beam,the pulse rate of 12T/s is required in BRing.The correlated painting schemes are adopted in BRing to further improve the particle injection efficiency.The schemes require a broadened range of good field regions,and thus higher requirements of magnets are needed.In addition,for the high energy,the maximum beam rigidity of BRing reaches 34 T m,and the widened magnetic field range of the dipole magnet is from 0.047 T to 1.58 T.In the fast ramping model,the eddy current induced by changing magnetic field can distribute in the yoke,coil,vacuum tube,etc.Firstly,the eddy current can lead to magnetic field delay and distortion,which affect the beam Trajectories and the size of envelopes.In addition,the eddy current will cause an additional power loss and the overheating of the vacuum tube,which in turn leads to the instability of the power supply and the damage to the ultrahigh vacuum environment.Moreover,with long-term running,fatigue failure of connecting bolts between the coils and iron yoke may occur.On the basis of extensive investigation,this paper carried out the optimization design of the steady-state magnetic field,the analysis of the dynamic effect of the magnetic field,the stability analysis of magnet structure,and the research of core technology and magnetic field measurement.1)Firstly,the magnetic field uniformity in high,medium,and low fields can reach the design requirement by using double air slots and pole shimming.Based on the two-dimensional optimization calculation,the linear programming algorithm is applied to the three-dimensional magnetic field optimization,which greatly improves the uniformity of the integrated magnetic field(<±2×10^-4@0.047 T～1.58 T).2)Secondly,the calculations of eddy current in the yoke,coil,and vacuum pipe are performed to study the eddy current effect in the fast ramping model by using various new modeling strategies.The optimized fixed structure of the coil is determined for fast ramping dipole magnets,and the related structural analysis is completed to confirm the structural reliability.3)Finally,the measurement system platform is designed and built.The steady-state magnetic field measurements and the second chamfer is performed to meet the requirements of magnetic field uniformity.The dynamic magnetic field measurement was performed to confirm the dynamic calculation results.The reliability of the fixation scheme was verified by the strain test of the coil fastening screw.According to the measurement,the prototype of BRing fast ramping dipole magnet meets the engineering application requirements.