Abstract: According to the invention, a magnetic field gradiometer detector for detecting a material of interest positioned in a detecting region outside the detector includes a transmitter for generating an output signal at a selected frequency, a receiver for detecting the signal, a probe, and a switch coupling the receiver and transmitter with the probe that alternately connects and disconnects the receiver and transmitter to the probe, switching between transmitting and receiving. The probe includes tuning elements and a gradiometer coil array. The gradiometer coil array includes a first surface coil and a second surface coil wound in an opposite sense, the probe having a first side and an opposite second side, with the first and second surface coils configured asymmetrically such that the probe projects a magnetic field in the outside detecting region adjacent to the first side while being self-shielded on the second side.

Abstract: A nuclear quadrupole resonance (NQR) method and probe for generating RF magnetic fields in different directions to distinguish NQR from acoustic ringing induced in a sample. Generally, an RF magnetic field is generated along an axis towards a sample to induce a resonance signal in the sample. The resonance signal includes NQR and acoustic ringing. The resonance signal is detected along the RF magnetic field axis. The acoustic ringing is detected along a direction orthogonal to the RF magnetic field axis. As a result, the NQR in the resonance signal can be distinguished from the acoustic ringing in the resonance signal.

Abstract: A nuclear quadrupole resonance (NQR) method and probe for generating RF magnetic fields in different directions to distinguish NQR from acoustic ringing induced in a sample. Generally, an RF magnetic field is generated along an axis towards a sample to induce a resonance signal in the sample. The resonance signal includes NQR and acoustic ringing. The resonance signal is detected along the RF magnetic field axis. The acoustic ringing is detected along a direction orthogonal to the RF magnetic field axis. As a result, the NQR in the resonance signal can be distinguished from the acoustic ringing in the resonance signal.