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ST4 - Improving the AC Sensitivity of an HTS SQUID using a Cooled LC Circuit
Improving the AC Sensitivity of an HTS SQUID using a Cooled LC Circuit
Longqing Qiu(1,2), Yi Zhang(1), Hans-Joachim Krause(1) and Alex I. Braginski(1)
INTRODUCTION: In some applications of superconducting quantum interference devices (SQUIDs), a high magnetic field sensitivity is needed only at a distinct frequency. In the case of low-temperature superconducting (LTS) SQUIDs, a resonant sensitivity enhancement may easily be realized using a resonant flux transformer, consisting of a pickup coil wound from niobium wire and a capacitor . In the case of HTS devices, however, only planar structures have been used to date, because flexible, bondable high- Tc wire of sufficient quality is not available yet.
It has been shown that resonant transformers made of normal conducting wires could improve the sensitivity of a SQUID from several kHz to about 1 MHz [2,3]. We reported recently on a new design of resonant-type coupling circuit suitable for high-Tc SQUID . This note is a short version of . Our LC circuit consists of only one coil which acts as both a pickup coil and an input coil. The coil surrounds the HTS SQUID within the liquid nitrogen bath and is shunted by a capacitor.