FIG. 4.
a: Experimental and calculated B1 field maps without (left) and with an uHDC block placed parallel (middle) and perpendicular (right) to B1 of the transmission coil. b: Three-dimensional vector plots of calculated B1 (black arrows with red flux lines) in a coronal plane and displacement current, Jd, (red purple arrows) distributions in the uHDC block of corresponding conditions. The B1 enhancement is produced by the large displacement current in the uHDC block when it is perpendicular to B1..