Design of Biplanar Coils for Degrading Residual Field in Magnetic Shielding Room
Jianzhi Yang, Xu Zhang, Bangcheng Han, Jing Wang, Ling Wang
Abstract
The uniform field and field gradient coils can be utilized for nulling background field inside magnetic shielding room (MSR), but the desired field produced by the coils is inevitably distorted due to the coupling effect of magnetic shielding material. To overcome this problem, an improved method is proposed based on the image method and target field method (TFM). Directed by this method, a series of bi-planar coils are designed to produce the uniform fields and field gradients for an active compensation in an MSR. Then, their finite element models and practical experiment are established to verify the effectiveness. Compared with the conventional target field method, the proposed method shows significant effects for both uniform field coils and field gradient coils. Uniformities of the Bx and Bz increase by 79.9% and 72.5%, and the dBx=dz and dBz=dz improve by 89.6% and 63.2%, respectively. It demonstrates that this method is adapted to design the bi-planar coils fixed in MSR and holds great promises for the active compensation of environmental magnetic field in the measurement of magnetoencephalogram (MEG).