A very high resolution thermometer for use below 7 K

Lipa, J. A.; Leslie, B.C.; Wallstrom, Timothy C.

doi:10.1016/0378-4363(81)90471-x

Cited by 32 publications

(15 citation statements)

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“…While we give a brief summary of our novel technique here, a more thorough discussion of our calorimeter appears in another article. [15] In short, our measurement takes the high resolution thermometers of Lipa and co-workers [16] as a point of departure. These authors used the paramagnetic salt Cu(NH 4 ) 2 Br 4 (CAB) as a thermometric element.…”

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confidence: 99%

Lambda Point in theH4e-Vycor System: A Test of Hyperuniversality

Zassenhaus

Reppy

1999

Phys. Rev. Lett.

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We have performed a high resolution specific heat measurement on 4 He completely filling the pores of Vycor glass. Within 10mK of the superfluid transition we have found a peak in the heat capacity which is only 0.02% the size of the background. The peak can be fit with a rounded version of the "logarithmic singularity" observed in bulk 4 He. Along with the previously observed "2/3" power law dependence of the superfluid density on temperature, this strongly suggests that the disorder imposed by the Vycor is irrelevant to the 3DXY superfluid phase transition. The critical amplitude of the peak, while in agreement with that found in other experiments in dilute superfluid 4 He, is considerably larger than that predicted by the theory of hyperuniversality.One of the foundations of the modern theory of critical phenomena is that all phase transitions are divided into a handful of universality classes, grouped together on the basis of a common symmetry and dimensionality in the ordered phase. Experimentally, one groups phase transitions on the basis of the powerlaws in the reduced temperature t = 1 − T /T C which thermodynamic properties follow very near to the transition temperature T C . The critical exponents of these powerlaws, which can be predicted to high accuracy thanks to the computational machinery of the renormalization group theory (RGT), are the same for all systems within a universality class.Because of its high purity, lack of strain, and the relative ease of precision measurement, the superfluid transition of 4 He is an unrivalled testing ground not only for determining the values of critical exponents but also for answering questions about universality. Very precise measurements of the specific heat of 4 He to within a few nK of T λ , the critical temperature of the superfluid transition, have confirmed the powerlaw The superfluid density has also been measured precisely and under the conditions of saturated vapor pressure is found to obey the powerlawwhere the critical exponent ν = 0.6702 and the critical amplitude ρ S0 = 0.351 g/cm 3 .[3] In both experimental quantities, the agreement between the experimentally determined critical exponents and precise RGT calculations is a stunning confirmation of our understanding of critical phenomena in pure systems.[4] The "logarithmic singularity" in the specific heat of equation 1 and the "2/3 power law" of equation 2 identify the superfluid transition of 4 He as a member of the 3DXY universality class.Another pillar in the theory of critical phenomena is the theory of hyperuniversality.[5] Hyperuniversality is a statement that the amount of energy (measured in units of k B T) per fluctuation is the same for all systems within a universality class. This is expressed by defining thewhere ξ 0 is the critical amplitude of the correlation length. RGT calculations find R = 0.96.[5] While ξ is not accessible directly, it can be calculated from the superfluid density by using the Josephson relation [6] The relation in equation 3 was tested by Ahlers and co-workers,...

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confidence: 99%

Lambda Point in theH4e-Vycor System: A Test of Hyperuniversality

Zassenhaus

Reppy

1999

Phys. Rev. Lett.

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“…and exceptional spatial resolution at thermometry stages located along the sidewall of the cell are required to observe definitively the nonlinear thermal conductivity regime discussed above. Thermometers, similar in design to those developed at Stanford University within Prof. John Lipa's group [7], have been manufactured for this experiment by our group in collaboration with J.P.L. These thermometers differ from the Stanford design only in that they are fabricated from aluminum (rather than copper) for better cosmic ray immunity once in orbit.…”

Section: Methodsmentioning

confidence: 99%

“…In transport measurements the system is held out of equilibrium and maintained in an exceptionally well-controlled steady-state condition. In these experiments, the thermal gradients very near the normal fluid-superfluid interface (HeI-HelI) are then measured with sub-nanokelvin-resolved thermometry [ 7 ]. Under gravity the position of the HeI-HelI interface may be set (or maintained) by adjusting (or regulating) the temperature of the superfluid component.…”

Section: Introductionmentioning

confidence: 99%

Critical dynamics in microgravity

Duncan

Boyd

Moeur³

et al. 1996

Int J Thermophys

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Although many well-controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven very far away from equilibrium as the transition occurs. Here we propose to measure the thermal gradient across the superfluid (HelI)--normal fluid (HeI) interface in microgravity conditions as a function of the heat flux Q used to make the measurements. Microgravity conditions are required (1) to avoid the hydrostatic pressure variation along the height of the helium column (a concern for Q<0.1pW.cm-2), (2) avoid convection in He-I for Q> 3pW-cm -2 in our apparatus, and (3) to increase the Q = 0 interfacial width from its value of a few tens of microns on Earth to about a millimeter in orbit. New technologies described in this paper are under development for this experiment, which is in definition for Space Shuttle flight.

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“…This manufacturing method provides a much more robust and superior thermal anchoring between the PdMn element and the sample stage than may be achieved in conventional designs that use paramagnetic salts, such as Cu(NH 4 ) 2 Br 4 + 2H 2 O or GdCl 3 as the thermometric element [12].…”

Section: Thermometer Design Assembly and Performancementioning

confidence: 99%

New Paramagnetic Susceptibility Thermometers for Fundamental Physics Measurements

Sergatskov¹,

Day

Бабкин³

et al. 2003

AIP Conference Proceedings

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Abstract. New paramagnetic susceptibility thermometers have been developed for use in fundamental physics missions in earth orbit. These devices use a SQUID magnetometer to measure the variation in the dc magnetization of a thermometric element that consists of a dilute concentration of manganese in a palladium matrix. Near 2.2 K these new PdMn thermometers have demonstrated a temperature resolution of better than 100 pK/ Hz and a time constant of 50 ms when operated with a 50 K/W thermal resistance to the liquid helium sample. These thermometers have been observed to be remarkably stable, with a drift of less than 10 fK/s. The observed power spectral density of the noise from these thermometers is consistent with separate measurements of the device's time constant and thermal standoff from the bath. Recently these PdMn materials have been made into thin films and microstructures for use in future studies of quantum liquids, and for possible use in a new class of bolometers and radiometers. These thermometers have been integrated into an experimental cell and thermal isolation network that are adequate to keep stray heats stable to within a few picowatts, with no systematic temperature errors greater than 60 pK, over the course of a planned fundamental physics experiment on Earth orbit.

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A very high resolution thermometer for use below 7 K

Cited by 32 publications

References 1 publication

Lambda Point in theH4e-Vycor System: A Test of Hyperuniversality

Lambda Point in theH4e-Vycor System: A Test of Hyperuniversality

Critical dynamics in microgravity

New Paramagnetic Susceptibility Thermometers for Fundamental Physics Measurements

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