[O-2-258] Coupled circuit simulation of Z- and X-gradient eddy currents in a 9.4T narrow-bore MRI system
Details analysis of eddy current parameters, eddy current fields has been conducted for 9.4T narrow-bore (53.84mm diameter, length 971mm) superconducting MRI system. MRI system has three inner cylindrical conducting (Cu - C1220) layers with diameters respectively, 53.84mm, 61.14mm, 69.74mm and thickness 2mm, 1.63mm, 1.63mm. Eddy current analysis has been conducted for both Z- and X-gradient coils. Simulation model is presented in Fig.1. The conducting structures are divided into sublayers and subdomains with thickness much smaller than skin depth [1]. For example, the innermost bore is divided into 20 sublayers and 84 subdomains in each sublayer. Inductive couplings between coil and subdomains are calculated by solid angle form of Biot-Savart law [1,2]. A new approach of calculating solid angle of Gx cylindrical coil has been suggested in Fig. 2. This approach is fast, computationally less complex, can calculate in continuous time domain. Results for Gx coil induced eddy current parameters -amplitudes and time-constants- for one layer are illustrated in Fig.3, Fig.4, respectively. Ref.[1] M.S.H. Akram et al, Jour. Magn. Reson., May, 2014. [2] W T Scott, The phys elect & mag, 1959.
