Magnetic field simulation of golay and maxwell coils

Abstract

Magnetic field gradient coils are essential in obtaining accurate magnetic resonance imaging (MRI) or nuclear magnetic resonance (NMR) signals by generating magnetic field gradient in each x, y and z direction. Two of the parameters to determine the performance of such gradient coils are the magnetic field linearity and magnetic field gradient uniformity. This research emphasizes on the analysis of the geometrical effect of the conventional Golay-Maxwell pair gradient coils to these two parameters through computer simulation. The results show that the geometrical parameters of ? and d affect Golay coil’s magnetic field gradient. Usable volume is improved 50% while gradient strength is increased 11% when ? is 1600 compared to the original 1200. The increase of d results in increase of usable volume, which is a maximum of 3374 cm3 at 0:8r but a loss of gradient strength of 36% compared to -0.34 mT/m at 0:2r. The other geometrical parameters of Golay coil are found not to affect much on the magnetic field gradient generated because of two reasons; the longitudinal sections of Golay coil do not contribute to Bz generation and the outer arcs are just acting as current return paths. For Maxwell coil, the usable volume can be improved until 19196.128 cm3 when d is 2:0r although the gradient value obtained is lower compared to a maximum of -0.066 mT/m at 1:2r. Application wise, the higher the gradient value and the bigger the usable volume, the better since the resolution can be improved, not to mention, a bigger specimen accomodation. A computer simulation is written fully in Open-source environment and feature variation of output as well as faster vectorized algorithm. The simulation results will definitely provide useful information for gradient coil designers without the need for physical development of prototype.