II. Applications of the Josephson Effect
II. Applications of the Josephson Effect
II. Applications of the Josephson Effect
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R. Gross, A. Marx, and F. Deppe © Wal<strong>the</strong>r-Meißner-Institut (2001 - 2013)<br />
4.1.5 Read-Out Schemes<br />
flux-locked loop:<br />
L f :<br />
feedback coil<br />
small flux change ±F to SQUID positive output / ±F<br />
increase <strong>of</strong> integrator output voltage<br />
increase <strong>of</strong> current through feedback coil<br />
compensates ±F<br />
SQUID voltage (and integrator output) stay constant null detector<br />
±V in / ±F ±I f = ±V in /R f ±F f = k 2 L f ±I f<br />
<strong>the</strong>n from |±F f | = |±F |:<br />
f mod » 100 kHz – several MHz: bandwidth up to 100 kHz, dynamic range ¸ 140 dB<br />
“slew rate”: up to 10 7 © 0 /s<br />
AS-Chap. 4 - 30
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