Manouchehr Takrimi1 and Ergin Atalar1,2
1National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
1National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
A novel gradient set consisting of two separate arrays is proposed. One array is used for the main coil and another one acts as an active shield. It is shown that proper feeding of both arrays delivers much higher functionality than conventional gradient systems.
Figure 3: BZ field plot of the
same z-gradient coil shown in Fig. 2 which is shielded by an active-shield
array consisting
of 10 pairs of uniformly-spaced and independently fed wire
loops of diameter 786 mm and total height of 1.6 m. The RMS of all feeding
currents (both of the main coil and its shield) is 0.46 A. An
efficiency of 8.7 $$$\mu$$$T/m/Arms and 7.9% deviation from
linearity can be seen within the same FOV diameter. A 10 mm thick cylindrical aluminum cryostat of
diameter 910 mm is shown by thick vertical purple lines at both sides.
Figure 4: BZ field plot of double-gradient z-gradient array along with its dedicated active-shield array
fed by a set of trapezoidal currents of proper amplitudes. The main z-gradient
array consists of 10 pairs of the same copper wires of diameter 680 mm and
height 1.2 m where the coil axis coincides with the z-axis. The shield configuration is exactly the same
shown in Fig. 2 except with new optimized currents. The RMS of all feeding currents is 0.62 A. An efficiency of 8.27 $$$\mu$$$T/m/Arms and 10.1% deviation from linearity is seen within both
FOVs. Both FOV diameters are 300 mm.
