Spectroscopic rotating-frame NQR imaging ( rho NQRI) using surface coils

An NQR imaging procedure is suggested in analogy to NMR rotating frame zeugmatography. No magnetic field gradients are used. The absence of readout gradients means in particular that the full spectroscopic information is accessible. It is demonstrated that the gradients of the radio-frequency amplitude which are needed for this technique can be produced by surface coils. In a certain distance range from the coils, these gradients are practically constant. The prominent advantage of surface-coil NQR is that objects larger than the coil diameter can be investigated. The imaging procedure then provides depth resolution in a range of the order of the coil radius. The technique is particularly suitable for the detection of gradients of physical parameters influencing the NQR line shift and of spatial distributions of the chemical composition. Examples are stress or pressure and temperature gradients. The latter has been demonstrated with the aid of a test object suitable for the production of such gradients. Images of the one-dimensional temperature distribution are shown.