Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Fabrication and statistical characterization of Nb SQUID sensors for multichannel SQUID system

  • Kim, B.K. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science) ;
  • Yu, K.K. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science) ;
  • Kim, J.M. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science) ;
  • Kwon, H. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science) ;
  • Lee, S.K. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science) ;
  • Lee, Y.H. (Quantum Magnetic Measurement Team, Korea Research Institute of Standards and Science)
  • Received : 2020.12.15
  • Accepted : 2020.12.30
  • Published : 2020.12.31
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Abstract

We fabricated superconducting quantum interference devices (SQUIDs) based on Nb Josephson junctions, and characterized the key parameters of the SQUIDs. The SQUIDs are double relaxation oscillation SQUIDs (DROSs) having larger flux-to-voltage transfer coefficient than the standard DC-SQUIDs. SQUID sensors were fabricated by using Nb junction technology consisted of a DC magnetron sputtering and a conventional photolithography process. In multichannel SQUID systems for whole-head magnetoencephalography measurement with a helmet-type SQUID array, we need about 336 SQUID sensors for each system. In this paper, we fabricated a few hundred SQUID sensors, measured the critical current, flux modulation voltage and decided if each tested SQUID can be used for the multichannel systems. As the criterion for the acceptance of the sensors, we chose the critical current and amplitude of the modulation voltage to be 8 ㎂ and 80 ㎶, respectively. The average critical current of the SQUIDs was 10.58 ㎂. The typical flux noise of the SQUIDs with input coil shorted was 2 μΦ0/√Hz at white region.

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References

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