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Research:

Low-Temperature Experimental Physics and Applied Physics, including SQUID-based magnetic measurement, low-temperature magnetic detectors, superfluid helium, magnetic thermometry, and cooling technology.

Research Topics

Low-Temperature Magnetic Detectors

Current research in collaboration with STAR Cryoelectronics. Shown here is the new (Jan. 08) layout for the miniature SQUID-based magnetic gradiometer with integral magnetizing field coils and persistence switch. This device will be used to study the temperature-dependent magnetization of very small samples ~50 micron. Pads for the electrical connections to the SQUID are on the right. The two large pads on the left are for the two spiral magnetizing field coils located in the middle of the chip, one centered over each pickup loop. The smaller pads on the left are for the persistence switch. The enlargement on the right shows a ~50u dia sample loaded into a pickup coil.

Recent Stuff:

• Characterization of a miniature thin-film SQUID susceptometer for metallic magnetic microcalorimetry, S.T.P. Boyd, R. Cantor, V. Kotsubo, P. Blumenfeld, J.A. Hall, J. Low Temp. Phys. 151, 369 (2008).
• Miniature Thin-Film Superconducting Quantum Interference Device Susceptometer, Robin Cantor, J. Ad Hall, Phil Blumenfeld, and Stephen T. P. Boyd, IEEE Trans. Appl. Superconductivity 17 (2), 738 (2007).

Properties of Helium-4 Near its Superfluid Transition

In 4He very near the Lambda Transition, when a uniform heat flux is directed downwards, parallel to the force of gravity, the divergent thermal resistivity of the helium allows it to self-organize into a state ("SOC") in which the temperature profile exactly follows the pressure-induced variation of T_lambda, plus a small offset which is determined by the heat flux magnitude. This highly nonlinear thermal system supports a temperature wave which propagates upwards only. We are currently analyzing the last of the data obtained by the sidewall-thermometry "DYNAMX" experiment (PI: Rob Duncan), which has the highest heat flux and AC drive levels ever observed for the SOC.

Recent Stuff:

• Effect of Inhomogeneous Heat Flow on the Enhancement of Heat Capacity in Helium-II by Counterflow near Tλ, STP Boyd, AR Chatto, RAM Lee, RV Duncan, and DL Goodstein, Proceedings of the 24th International Conference on Low Temperature Physics, AIP Conference. Proceedings. 850, 133 (2006).
• CW Measurement of the Upward-Going Temperature Wave in the Helium-4 Self-Organized Critical State, STP Boyd, DA Sergatskov, and RV Duncan, Proceedings of the 24th International Conference on Low Temperature Physics, AIP Conference Proceedings 850, 135 (2006).

Cryogenic Technology

Design Tool (Try This!): Cryogenic Vacuum Current Lead Calculator/Designer/Optimizer
Selected Recent Presentations
"Cat's Cradle" Fiber Suspension Thermal Standoff Development (stress analysis for third test piece)

Teaching

People/Contact

Lab Internal Pages

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The research described on this site has been funded in part by NASA.

Note: this site will probably always be "under construction," and there will always be some areas needing more info. If you have questions, please send an email.

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