In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution-generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2 . Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO(x)-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described. In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localization capability is similar to that usually achieved with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundred pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be a combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor of 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO x-PbAuIn Josephson tunnel junctions. Some possible improvements are also described.
Carelli, P., Chiaventi, L., Leoni, R., Pullano, M., SCHIRRIPA SPAGNOLO, G. (1991). A planar second-order DC SQUID gradiometer. CLINICAL PHYSICS AND PHYSIOLOGICAL MEASUREMENT. SUPPLEMENT [10.1088/0143-0815/12/B/002].
A planar second-order DC SQUID gradiometer
SCHIRRIPA SPAGNOLO, Giuseppe
1991-01-01
Abstract
In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution-generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localisation capability is similar to that one usually achieves with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundreds of pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be the combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2 . Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO(x)-PbAuIn Josephson tunnel junctions. Some possible improvements will also be described. In this work we describe a DC SQUID gradiometer, sensitive to the second spatial derivative of the magnetic field. The sensitive area of the gradiometer is the inductive body of the DC SQUID itself. The isoflux line distribution generated by a dipolar source, obtained by performing magnetic measurements with an array of such detectors, is relatively complicated, but its localization capability is similar to that usually achieved with axial detector arrays. Planar gradiometers also show a better resolution for near sources and a stronger rejection of far disturbances. The final device is expected to have an inductance of a few hundred pH in order to obtain performances typical of a low noise DC SQUID. The pick-up coils will be a combination of four square holes of 500 μm side with a 1.05 cm baseline. Due to the magnetic field concentration (in the final device it can be a factor of 10) the gradiometer will have a sensitivity of 10 -11 T m -2 Hz - 1/2 and a field sensitivity of about 2 fT Hz - 1/2. Some preliminary results, obtained on detectors with an intermediate area between the prototype and final device, are reported here. The process used to fabricate this second-order gradiometer is based on Nb-NbO x-PbAuIn Josephson tunnel junctions. Some possible improvements are also described.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
