Within the same area, sensitive
gradiometers detected magnetic signs of cooking hearths and pot fragments.
Current gravimeters have been used in the air with some success in defining features with a scale of 10 km or greater, but the next generation of airborne gravity instruments will be
gradiometers targeting features 200 to 500 m beneath the ground surface with density contrasts about 300 kg/m3 and smaller than 1 km across.
Using superconductivity, the devices could be built as
gradiometers able to measure magnetic gradients in particular orientations and provide vectors of the magnetic dipoles.
A whole-scalp MEG system (306 channels; 204 planar
gradiometers and 102 magnetometers; Vectorview[TM]; Elekta Oy, Helsinki, Finland) was employed for the recordings.
Methods: Magnetocardiographic mapping is performed with a 36-channel unshielded mapping system, based on DC-SQUID sensors coupled to second-order axial
gradiometers (pick-up coil 19 mm and 55-70 mm baselines; sensitivity of 20 fT/[square root of Hz] in above 1 Hz), as part of the electrophysiologic investigation protocol, tailored to the diagnostic need of each arrhythmic patient.
Researchers around the world are also pursuing the promise of quantum improvements for other instruments, including gyroscopes used in navigation systems, atomic clocks, and gravity-measuring devices, or
gradiometers, that guide oil exploration and geophysical research.
Geoscan Research of Bradford, U.K., is manufacturing three microprocessor-controlled fluxgate
gradiometers having 0.5 m separation of the sensors.
The Navy already uses precision-machined electromechanical gravity
gradiometers to help submarines navigate without noisy sonar.