Nuclear magnetic resonance detector used for reducing probe ringing

Abstract

A toroid cavity detector includes an outer cylindrical housing through which extends a wire along the central axis of the cylindrical housing from a closed bottom portion to the closed top end of the cylindrical housing. In order to analyze a sample placed in the housing, the housing is placed in an externally applied static main homogeneous magnetic field (B,). An RF current pulse is supplied through the wire such that an alternately energized and de-energized magnetic field (B,) is produced in the toroid cavity which B,field is oriented perpendicular to the B,field. Following the RF current pulse, the response of the sample to the applied B,field is detected and analyzed. In order to minimize the detrimental effect of probe ringing, the cylindrically shaped housing is elongated sufficiently in length so that the top and bottom portions are located in weaker, fringe areas of the static main magnetic B,field. In addition, a material that tends to lessen the effect of probe ringing is positioned along the top and bottom ends of the toroid cavity. In another embodiment of the present invention, a plug is positioned adjacent the inside of the top and bottom ends of the toroid cavity so that the sample contained in the toroid cavity is maintained in the strongest and most homogeneous region of the static magnetic B,field.