Abstract: This method and apparatus are directed to baggage inspection, and more particularly, baggage inspection to locate explosives. In the preferred and illustrated embodiment, a conveyor system is utilized to transport a bag past a first magnet to achieve an initial nuclear magnetic resonance (NMR) polarization of a selected element. The element in the preferred embodiment is hydrogen, it being noted that hydrogen in explosives has a long T.sub.1 and a short T.sub.2. The first magnet provides an initial polarization. The bag continues on the conveyor belt past a second magnet. The second magnet provides the measurement field intensity and a coil contains an interacting RF forming the interrogation pulses. Echos are received. In the preferred embodiment, first and subsequent second echos are received and stored. The two signals are subtracted from one another to a null. The NMR response of elemental hydrogen in compounds typified by explosives (having a long T.sub.1 and short T.sub.

Abstract: This disclosure is directed to an acoustic Barkhausen stress detector apparatus and a method of obtaining measurements of stress in or determination of the microstructure of ferromagnetic materials. In the preferred and illustrated embodiment, stress or microstructure information in a ferromagnetic specimen is tested and measured through application of a variable magnetic field. A sensitive acoustic detecting device including an input transducer(s) and amplifier(s) forms a signal based on Barkhausen acoustic phenomena which arise from a change in the magnetic field strength. Barkhausen acoustic information is in the form of vibrations produced within the material which occur as magnetic domain walls shift. The domain wall shifts occur at various locations within the material of interest, and the acoustic vibrations are propagated through the material and are observable at the surface by one or more transducers.

Abstract: A method and apparatus for enhanced nuclear magnetic resonance (NMR) discrimination and detection is disclosed. In the preferred embodiment, a sample which has a first atomic element is placed in a magnetic field of a first intensity. A reaction between the nuclei of the first atomic element and the electromagnetic field of the apparatus produces an NMR response which is tunable with field intensity. If the first atomic element of interest is present and intimately comingled with a second atomic element of interest, as might occur in compounds, and if the second element of interest has a nuclear quadrupolar moment and if the molecular structure conditions are proper for it to have a nuclear quadrupolar resonance (NQR), then adjustment of the magnetic field intensity varies the NMR frequency of the first element of interest to coincide with the NQR frequency of the second element of interest.