Refrigeration and thermometry of liquid {sup 3}He-{sup 4}He mixtures in the ballistic regime

Journal Article · Tue Nov 01 04:00:00 EST 1994 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00752921· OSTI ID:98789

Koenig, R; Betat, A; Pobell, F ^[1]

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1. Universitaet Bayreuth (Germany)

The ballistic regime of liquid {sup 3}He-{sup 4}He mixtures is characterized by a large mean free path {lambda} of the thermal excitations compared to the characteristic dimension of the experiment. We report on investigations of the transport properties of mixtures as well as superfluid {sup 3}He in the ballistic regime by means of the vibrating wire technique. In order to avoid possible sources of heat leaks into the liquid, the experimental setup was built as far as possible of pure materials only. The contribution of a Ag sinter to the heat leak as well as its influence on the attainable minimum temperature of the mixtures were investigated by performing measurements in two similar setups which differed in the size of the heat exchanger by about one order of magnitude. Moreover, we have used the vibrating wire partly immersed in the superfluid {sup 3}He-B phase of a phase-separated mixture as a very sensitive, continuously monitoring thermometer for liquid mixtures in their ballistic regime. The achieved minimum temperature of a 6.8%-mixture at p = 0.35 bar and of a 9.5%-mixture at p = 9.8 bar was 130 {mu}K. This value can be considered as an upper limit for the temperature of the mixtures as the damping of the vibrating wire thermometer saturates at this temperature due to its intrinsic properties.

• Sponsoring Organization: USDOE
• OSTI ID: 98789
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 3-4 Vol. 97; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
66 PHYSICS
HELIUM 3
HELIUM 4
MEAN FREE PATH
MIXTURES
REFRIGERATION
TEMPERATURE DEPENDENCE
TEMPERATURE MEASUREMENT
THERMOMETERS