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Published September 7, 2006 | Published
Book Section - Chapter Open

Measurement of the SOC State Specific Heat in ^4He


When a heat flux Q is applied downward through a sample of liquid 4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity induced gradient in Tlambda. All the helium in the sample is then at the same reduced temperature tSOC = ((T[sub SOC] - T[sub lambda])/T[sub lambda]) and the helium is said to be in the Self-Organized Critical (SOC) state. We have made preliminary measurements of the 4He SOC state specific heat, C[del]T(T(Q)). Despite having a cell height of 2.54 cm, our results show no difference between C[del]T and the zero-gravity 4He specific heat results of the Lambda Point Experiment (LPE) [J.A. Lipa et al., Phys. Rev. B, 68, 174518 (2003)] over the range 250 to 450 nK below the transition. There is no gravity rounding because the entire sample is at the same reduced temperature tSOC(Q). Closer to Tlambda the SOC specific heat falls slightly below LPE, reaching a maximum at approximately 50 nK below Tlambda, in agreement with theoretical predictions [R. Haussmann, Phys. Rev. B, 60, 12349 (1999)].

Additional Information

© 2006 American Institute of Physics. Issue Date: September 7, 2006. We would like to thank Dmitri Sergatskov, Steve Boyd, Alex Babkin, Alexander Churilov, and Talso Chui for helpful discussions and assistance with cell construction and cryovalve assembly and operation. This work was supported in part by the Fundamental Physics Discipline of the Microgravity Science Office of NASA.

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