Progress in Superconductivity

The Korean Superconductivity Society (한국초전도학회)
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Design and Characterization of Low-noise Dewar for High-sensitivity SQUID Operation

고감도 SQUID 냉각을 위한 저잡음 듀아의 설계 및 특성 조사

  • Yu, K.K. (Brain and Cognition Measurement Lab, Korea Research Institute of Standards and Science) ;
  • Lee, Y.H. (Brain and Cognition Measurement Lab, Korea Research Institute of Standards and Science) ;
  • Kim, K. (Brain and Cognition Measurement Lab, Korea Research Institute of Standards and Science) ;
  • Kwon, H. (Brain and Cognition Measurement Lab, Korea Research Institute of Standards and Science) ;
  • Kim, J.M. (Brain and Cognition Measurement Lab, Korea Research Institute of Standards and Science)
  • Received : 2010.03.22
  • Accepted : 2010.04.15
  • Published : 2010.04.30
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Abstract

We have fabricated the low noise liquid helium(LHe) dewar with a different shape of thermal shield to apply the 64-channel SQUID(Superconducting Quantum Interference Device) gradiometer. The first shape of thermal shield was made of an aluminum plate with a wide width of 100 mm slit and the other shape was modified with a narrow width of 20 mm slit. The two types of dewars were estimated by comparing the thermal noise and the signal-to-noise ratio(SNR) of magnetocardiography(MCG) using the $1^{st}$ order SQUID gradiometer system cooled each dewar. The white noise was different as a point of the dewar. The noise was increased as close as the edge of dewar, and also increased at the thermal shield with the more wide width slit. The white noise of the dewar with thermal shield of 100 mm slit was 6.5 fT/$Hz^{1/2}$ at the center of dewar and 25 fT/$Hz^{1/2}$ at the edge, and the white noise of the other one was 3.5 - 7 fT/$Hz^{1/2}$. We measured the MCG using 64-channel SQUID gradiometer cooled at each LHe dewar and compared the SNR of MCG signal. The SNR was improved of 10 times at the LHe dewar with a modified thermal shield.

Keywords

References

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