High Resolution Thermometry Using the Magnetic Penetration Depth of Superconducting Films

  • C. J. Yeager
  • P. J. Shirron
  • M. J. DiPirro
Part of the Advances in Cryogenic Engineering book series (ACRE, volume 43)

Abstract

A Penetration Depth Thermometer (PDT) has been under development for potential use in microgravity critical point experiments. The active element is a superconducting film whose thickness is comparable to the magnetic penetration depth (5–20 nm). Field penetration is strongly temperature dependent just below the transition (~0.9 – 1.0 Tc). Fields are generated and sensed by using excitation and pickup coils located near the film. Using a dc SQUID sensor for readout, temperature resolution on the order of 0.1 nK/✓Hz can be obtained. Earlier work using aluminum films (Tc=1.69 K) demonstrated a maximum sensitivity of 1 nK/✓Hz. Improvements in coil design have since yielded a factor of 3 improvement. PDT’s have been made with aluminum films deposited on a planar sapphire substrate with transition temperatures greater than the lambda point in superfluid helium. For performance tests, a cryostat has been constructed where the PDT will be in an experimental cell filled with superfluid. This will provide thermal stability better than 0.1 nK/✓Hz . Results of the current design are presented.

Keywords

Critical Current Aluminum Film Superfluid Helium Secondary Coil Primary Coil 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • C. J. Yeager
    • 1
  • P. J. Shirron
    • 1
  • M. J. DiPirro
    • 1
  1. 1.NASA/Goddard Space Flight CenterGreenbeltUSA

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