Purpose: Size of scanning system in particle beam therapy can be reduced by using a combined function scanning magnet compared to separated scanning magnets. We propose a combined function scanning magnet with distributed winding coils (DW-SCM). Its homogeneity of the dipole magnetic field and the correction method of the magnetic field are experimentally verified.
Methods: DW-SCM can generate the rotating dipole magnetic field by the three-phase sinusoidal current. By changing balance of the three-phase current, the good field region (radius) of field homogeneity within ± 0.5% can be expanded. We have made a prototype of DW-SCM with 30 mm bore diameter which is one-third the actual size of the actual one. It consists of 12 magnetic poles and 3 coils of hollow conductors. The magnetic field distribution in the scanning direction with respect to the central magnetic field has been measured to evaluate the good field region with and without the correction.
Results: The measured magnetic field distribution of the protype DW-SCM within the good field region is in agreement with the simulation results calculated by Poisson Superfish code by 0.01%. The good field region after applying the correction was 15 mm which is 50% of the bore diameter.
Conclusion: We have made the prototype of DW-SCM and evaluated the good field region. After applying the magnetic field correction, the good field region reaches 50% of the bore diameter.
Protons, Radiation Therapy, Magnetic Fields
TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)