Nuclear magnetic resonance apparatus and method

Abstract

A nuclear magnetic resonance sensing apparatus, comprising a magnet for inducing a static magnetic field in a region containing materials to be analyzed. The magnet has a longitudinal axis and substantially uniform magnetization along the axis. The apparatus includes a system for generating a radio frequency magnetic field to excite nuclei of the materials to be analyzed, which includes a first antenna having an axial length shorter than a length along the axis over which the magnet has said substantially uniform magnetization. The axial length of the first antenna is shorter in a direction of motion of the apparatus so that the radio frequency magnetic field excites the nuclei where they are substantially prepolarized by the static magnetic field to an equilibrium state along the direction of motion. The apparatus includes a system for receiving nuclear magnetic resonance signals from the excited nuclei. In a particular embodiment, the receiving system includes a second antenna having a sensitive length shorter than the axial length of the first antenna in the direction of motion, so that the second antenna detects nuclear magnetic resonance signals from substantially fully radio frequency excited nuclei in the materials to be analyzed.