Abstract: An elongated probe suitable for lowering down a borehole for nuclear magnetic logging has a pair of similar cylindrical magnets 1 and 2 separated by a gap in which a solenoid 3 is symmetrically disposed. The solenoid has a core 4 of high permeability ferrimagnetic material and has a length preferably equal to half the length of the gap. The magnets 1 and 2 and solenoid 3 with its core 4 are contained within a hollow cylindrical casing 5 of non-magnetic material.

Abstract: A sensing apparatus has a probe displacement with respect to a support arm and to a reference position. The probe has a flat disc mounting three transducers which are spaced apart from one another at regular intervals. Each transducer has an elastomeric dielectric and is capable of producing an electrical output signal in response to displacement of the probe from the reference position. An electrical circuit compares output signals produced by the transducers and evaluates the direction and/or extent of probe displacement. Such evaluation may be used in the manipulator control system of an article-handling equipment.

Abstract: In an NMR examining arrangement for producing an image of a region, generally a planar slice, of a body, it has been suggested to derive, from the resonance signals, a plurality of values, for strips in the slice, and then to convolve them with a convolution function to be suitable for back projection in the manner known for x-ray signals. In this invention it is proposed to modulate the resonance signals with a suitable function and then to Fourier transform them but not to convolve them. The modulation function is chosen to give after Fourier transformation the same effect as the convolution would have given. It is suggested that the modulation function should be the inverse Fourier Transform of the desired convolution function.

Abstract: Nuclear magnetic resonance (NMR) apparatus have beenproposed for examining slices or volumes of bodies, perhaps for medical examination of patients. Magnetic fields are used to induce resonance in a selected region of a body and a resonance signal is detected during a pulse of a gradient field which causes phase dispersion across the region.It is now proposed that more efficient operation of the apparatus is possible if the gradient pulse is a non-square pulse, perhaps a distorted sinusoid, and the resonance signal is sampled during that pulse at intervals such that .intg. Hdt is substantially equal between adjacent samples.

Abstract: In a nuclear magnetic resonance imaging apparatus it has been proposed to excite resonance preferentially in a cross-sectional slice of a patient's body by applying a field gradient pulse in conjunction with a pulse of RF. It has been found that the shape of the RF pulse envelope can be chosen to reduce excitation outside the chosen slice. It is proposed that the RF envelope should be a unidirectional pulse of which both the rising and falling parts are monotonic curves lying between limits given by sin.sup.3 t and sin.sup.10 t curves, preferably sin.sup.5 t. An acceptable curve may fall below sin.sup.10 t in the skirts but should not change sign.

Abstract: In an apparatus for examining human bodies by nuclear magnetic resonance to produce images of cross-sectional slices of such bodies, it is desirable to reduce the recovery time between scans at different angles. A suitable pulse sequence for examination with minimum dispersion is disclosed. Repetition of the sequence with inverted pulses to drive the spins back to equilibrium and reduce recovery time is also disclosed.