Third sound experiments and phase separation in /sup 3/He - /sup 4/He mixture films

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6740744

Ellis, F M

The first experiment dealt with first pure /sup 4/He films, where a capacitive third sound detection technique was developed and allowed the direct sensing of third sound height oscillations in unsaturated films. The relation between these height oscillations and the corresponding thermal oscillations was found to agree at least qualitatively with those predicted by Bergman. A variety of mixture films were then studied, both with bolometers and capacitors, where it was realized that interesting structure in the third sound velocity could not be attributed solely to the properties of the film, but involved capillary condensation in packed powder used as surface reservoirs. The second experiment attacked this problem with a cell designed to minimize capillary condensation and accurately characterize the film. Here it was found that for all of the films studied, the third sound was described quite well by a model nearly completely phase separated film. This was inconsistent with the conclusions by Laheurte based on observations made on similar films. A variety of anomalous pulse shape effects are also described. The final experiment pushed the layered model of phase separation to the limits of colder temperatures and thinner coverages of /sup 3/He. A very sensitive resonance technique was used which showed that even for /sup 3/He coverages where the layered model still applied. Measurements of the dissipation in these same films suggests that there is more interesting physics taking place in the film's surface than the third sound velocity would indicate alone.

• Research Organization: Massachusetts Univ., Amherst (USA)
• OSTI ID: 6740744
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DATA
DISPERSIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
FILMS
HELIUM 3
HELIUM 4
HELIUM ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MIXTURES
NUCLEI
NUMERICAL DATA
PHASE TRANSFORMATIONS
STABLE ISOTOPES
SUPERFLUIDITY
SURFACE PROPERTIES
THIRD SOUND