NOISE-IMMUNE COIL FOR UNSHIELDED MAGNETIC-RESONANCE MEASUREMENTS

A modified split-loop resonator that is electrically balanced and that has no magnetic dipole moment is shown to be relatively immune to env ironmental noise. Using a magnetic resonance surface coil of this desi gn for N-14 NQR at 3.4 MHz, it is demonstrated that magnetic resonance measurements can be made in the laboratory without additional RF shie lding and with less than a 2 dB increase in the rms noise. Compared to more traditional designs, the modified split-loop resonator showed a net 17-dB gain in sensitivity for unshielded measurements. (C) 1998 Ac ademic Press.