Integrated DC SQUID magnetometer with high dV/dB
1991; IEEE Magnetics Society; Volume: 27; Issue: 2 Linguagem: Inglês
10.1109/20.133842
ISSN1941-0069
AutoresD. Drung, R. Cantor, Mark Peters, Tapani Ryhänen, H. Koch,
Tópico(s)Magnetic Properties and Applications
ResumoA directly coupled DC SQUID magnetometer with very simple feedback electronics is presented. The magnetometer has been integrated on a 7.2*7.2 mm/sup 2/ chip and fabricated using a four-level Nb/Si/sub x/N/sub y//Nb process. Eight pickup loops are connected in parallel to directly form the SQUID inductance of about 0.4 nH which leads to a high sensitivity B/ Phi =0.47 nT/ Phi /sub 0/. An additional positive feedback (APF) circuit on the magnetometer chip has been used to increase the gradient of the V- Phi characteristic to dV/d Phi approximately=300 mu V/ Phi /sub 0/ at the SQUID operating point. The resulting gradient of the transfer function dV/dB approximately=640 mu V/nT makes it possible to directly readout the SQUID without helium-temperature impedance matching circuits or flux modulation techniques. Using a highly simplified feedback electronics consisting of an ultra-low-noise bipolar preamplifier and an integrator on a 10-cm/sup 2/ PC board, a white noise level below 3 fT/ square root Hz with a 1/f corner frequency around 3 Hz, a 3-dB bandwidth of about 40 kHz, and a maximum feedback range of +or-32 nT for frequencies up to 300 Hz have been measured.
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