Research on The Electromagnetic Interference of Scanning Magnet Magnetic Field to Cable in Proton Therapy

Proton therapy is a new method to treat tumors. The main method of proton therapy is the pencil beam scanning (PBS), whose core component is the scanning magnets. The beam is deflected under the magnetic field of the scanning magnets. Various cables are arranged near the scanning magnets. The excitation current and magnetic field of the scanning magnets will cause electromagnetic interference to the surrounding cables. To reduce electromagnetic interference, the shielding structure is designed. In this paper, the type of cables near the scanning magnets is analyzed first. Then, using Computer Simulation Technology (CST) CABLE STUDIO, the magnet magnetic field is modeled, the influence of the magnetic fields on the strong electrical cables, weak electrical cables and multi-channel signal cables are simulated. This paper further analyzes the influence factors of the shielding frame such as the layer thickness, the size and the shielding material on shielding effect. It is concluded that the shielding effect of coaxial cable is better than that of single cable. The larger the thickness of the shielding frame, the smaller the size, the larger the conductivity and relative permeability of the shielding material, the better the shielding effect.