'Heat from Above' Heat Capacity Measurements in Liquid ^4He
Abstract
We have made heat capacity measurements of superfluid ^4He at temperatures very close to the lambda point, T_λ, in a constant heat flux, Q, when the helium sample is heated from above. In this configuration the helium enters a self-organized (SOC) heat transport state at a temperature T soc(Q), which for Q≥100 nW/cm^2 lies below T_λ. At low Q we observe little or no deviation from the Q=0 heat capacity up to T_(SOC)(Q); beyond this temperature the heat capacity appears to be sharply depressed, deviating dramatically from its bulk behaviour. This marks the formation and propagation of a SOC/superfluid two phase state, which we confirm with a simple model. The excellent agreement between data and model serves as an independent confirmation, of the existence of the SOC state. As Q is increased (up to 6 µW/cm^2) we observe a Q dependent depression in the heat capacity that occurs just below T_(SOC)(Q), when the entire sample is still superfluid, This is due to the emergence of a large thermal resistance in the sample, which we have measured and used to model the observed heat capacity depression. Our measurements of the superfluid thermal resistivity are a factor of ten larger than previous measurements by Baddar et al.
Additional Information
© 2004 Plenum Publishing Corporation. We are grateful to Dr Alexa Harter for many helpful discussions. The research reported in this paper was carried out in collaboration between Caltech, The University of New Mexico and JPL, and was supported by the Fundamental Physics Discipline of the Microgravity Science Office of NASA.Additional details
- Eprint ID
- 62969
- DOI
- 10.1023/B:JOLT.0000012601.63124.60
- Resolver ID
- CaltechAUTHORS:20151216-095248823
- NASA
- Created
-
2015-12-16Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field