A Study On The Multipole Scanning Magnet For Proton Therapy

With the development of radiotherapy technology,proton therapy has become one of the most advanced cancer treatment methods in the world due to its unique advantages in treatment.However,advanced proton therapy devices are often very large,especially the gantry,which makes the equipment expensive.As the main component of the treatment head,the scanning magnet is installed in the rotating gantry and the space it occupies determines the overall size of the rotating gantry to a certain extent.In order to reduce the space occupied by the scanning magnet and realize the miniaturization and compact development of the proton therapy equipment,the multipole scanning magnet has been proposed internationally in recent years.Based on the Shanghai Advanced Proton Therapy Facility,the paper introduces in detail the development process and results of the first multipole scanning magnet in China,including the design,simulation,fabrication and measurement results.Firstly,starting from the principle of multipole scanning magnet,the paper studies the development status of multipole scanning magnets and combines the design requirements of 360° rotating Gantry with Shanghai Advanced Proton Therapy Facility to determine the design scheme of the first multipole scanning magnet in China.Secondly,through the simulation analysis and optimization of the 2D and 3D static fields of the multipole scanning magnet,the design parameters are determined,and the maximum scanning range,good field size and field uniformity are proved to meet the design specifications.Then based on the model of single silicon steel sheet,the adjustment time of the multipole scanning magnet is determined by analyzing the influence of the eddy current during the magnetic field change of the multipole scanning magnet and the scanning error is analyzed in detail when scanning a circular path.At the same time,the paper also introduces in detail the design and machining of the multipole scanning magnet coils,and proposes the idea of perturbation method when calculating the inductance of multiple non-series coils.Finally,through the actual measurement of the 3D static field of the multipole scanning magnet,it is proved that the development of the multipole scanning magnet has reached the project design requirements.