Synchrotron magnet power supply network with normal and common modes including noise filtering

We study theoretical aspects of power supply network for synchrotron magnets, particularly the Heavy Ion Medical Accelerator Complex (HIMAC) system that operates with good stability. We introduce a simplified electric circuit model, which uses a thyristor rectifier power supply, a noise filter, and synchrotron magnets, to introduce the concept of the normal and the common modes. The normal and common modes become decoupled when all the electric loads are placed symmetrically around the ground line for a three line circuit system. This construction makes the normal mode the dominant control of the magnetic fields of the accelerator magnets. It is then found that the connection of the ground (common) line to the middle point of the thyristor power supply is essential to make the common mode stable. These two arrangements can remove the noise at high frequency in the normal mode by the noise filter and hence the noise in the magnetic fields, resulting in stable performance of the synchrotron network.