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arXiv · 1310.0078

A near-field scanning SQUID microwave microscope

Vladimir V Talanov·Nesco M Lettsome, Jr.·Valery Borzenets·Nicolas Gagliolo·Alfred B Cawthorne·Antonio Orozco
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Abstract

We developed a scanning DC SQUID microscope with novel readout electronics capable of wideband sensing RF magnetic fields from 50 to 200 MHz and simultaneously providing closed-loop response at kHz frequencies. To overcome the 20 MHz bandwidth limitation of traditional closed-loop SQUIDs, a flux-modulated closed loop simultaneously locks the SQUID quasi-static flux and flux-biases the SQUID for amplification of the RF flux up to $Φ_0/4$ in amplitude. Demodulating the SQUID voltage with a double lock-in technique yields a signal representative of both the amplitude and phase of the RF flux. This provides 80 dB of a linear dynamic range with the flux noise density of 4 $μΦ_0/\sqrt{Hz}$ at 200 MHz for $YBa_2Cu_3O_7$ bi-crystal SQUID at 77 K. We describe the electronics performance and present images for RF magnetic field of the travelling wave in a coplanar waveguide, the standing wave in an open-circuited microstrip, and a surface mounted device antenna.

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Vladimir V Talanov, Nesco M Lettsome, Jr., Valery Borzenets, Nicolas Gagliolo, Alfred B Cawthorne, Antonio Orozco. 2013-12-16. A near-field scanning SQUID microwave microscope. https://doi.org/10.1088/0953-2048%2F27%2F4%2F044032

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