External field-frequency lock probe for high resolution solid state NMR

A transmission line lock probe is described for magnetic field stabilization of a high field superconducting magnet with a significant drift rate for high resolution solid state NMR experiments employing a conventional magic angle spinning (MAS) probe. The lock probe connects to the standard spectrometer lock channel and employs a spherical sample bulb containing D2O doped such that the peak is homogeneously broadened despite the sample being displaced from the homogeneous central region of the static magnetic field. Use of a separate lock probe makes it possible to remove the MAS probe for changing samples while maintaining field-frequency lock. (C) 2005 American Institute of Physics.