DC SQUID SERIES ARRAYS WITH INTRACOIL DAMPING TO REDUCE RESONANCE DISTORTIONS

We report on low-noise DC SQUID series arrays incorporating intracoil damping, which show smooth DC characteristics. The voltage-flux charac teristics of these devices are reproducible upon repeated cooling and do not require multiple heating/cooling cycles to maximize peak-to-pea k output voltage modulation depth. The devices consist of 100 DC SQUID s with individual signal and feedback coils connected in series. The t otal input inductance is 600 nH, and the peak-to-peak output modulatio n is 4 mV with a transfer function of 350 V/A. The bandwidth is 5 MHz and the equivalent input current noise is approximately 2.5 pA/root Hz . With these characteristics, these devices are useful as preamplifier s for microcalorimeter X-ray detectors. Published by Elsevier Science Ltd.