Manouchehr Takrimi1 and Ergin Atalar1,2
1UMRAM, Bilkent University, Ankara, Turkey, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
1UMRAM, Bilkent University, Ankara, Turkey, 2Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
A novel
hybrid gradient coil consisting of two conventional actively-shielded x/y
gradient coils and a programmable active-shield z-gradient array coil is
introduced and simulated. The proposed gradient coil can dynamically provide different magnetic profiles for diverse
applications.
Figure 1: A quarter geometry of
the proposed gradient system. Z-gradient array consists of 12 pairs of wire bundles, each with 10
copper wires of 2 mm diameter. The diameter/height of the main and shield
array coils are 24/30 and 30/35 cm, respectively. Copper sheets of 2 mm
thickness and 40 cm height for the main coil and square copper wires (2x2
mm2) are used for shield coils. The diameter of the main/shield
coil for the x- and y-gradient coils are 20/26 and 22/28 cm, respectively. The
aluminum shell of 90 cm diameter (the warm cryostat) is not shown here.
Figure 4: The same gradient
system with the second configuration for the z-gradient array profile. In this
case, the FOV size is reduced to 60 mm and it is shifted up 30 mm along the
z-axis. Z-gradient strength is doubled to be 250 mT/m within the shifted FOV
region with less than 8.9% deviation from linearity. The contour lines indicate
1 mT separations. The residual
eddy current is 0.007%.
