Effects of the Spatial Offsets of Superconducting Coils on the Magnetic Field in SC200 Cyclotron

The SC200 superconducting cyclotron for hadron therapy is developed by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). However, the spatial shift of superconducting coils in a cyclotron will lead to the deviation of the magnetic from the requirements. It has an adverse effect on the acceleration of the beam. This article studies the effect of the tilt and horizontal offsets on the magnetic field in cyclotron. These two offsets can be detected by measuring the first harmonic of radial and axial components of the magnetic field on the midplane, respectively. Additionally, it is proved that the mixed offset of superconducting coils can be decomposed into these three fundamental offsets: vertical offset, tilt, and horizontal offset. Experimental data also indicate that this method can substantially reduce the first harmonic of the radial component of the magnetic field in the required area, which means that the superconducting coils are aligned in space.