Thermal buffering of cross-coils in high-power nmr decoupling

Abstract

A transverse rf saddle coil (,) for use in NMR is affixed in intimate thermal conract on one surface of a ceramic coilform (,) of high thermal conductivity. The probe is mostly for use with solid samples at high fields where the axis of the coilform is not alignedwith the main field. An orthogonal rf coil (,) is mounted in intimate thermal contact to the first saddle coil (,) via a ceramic spacer or coilform (,). The coilform is cooled by high-velocity gas flow and is also often associated with bearing exhaust gas from a high speed sample spinner. The two coils are tuned to different rf frequencies with circuits capable of supporting high rf currents. The rf coils (,) may be magnetically compensated and expansion controlled, and passive geometric compensation of magnetic susceptibility effects from a sample spinner stator may also be incorporated. Novel coil mounting techniques, including metallurgical bonds to ceramics and capturing by dielectric clam-shells, are also disclosed.