Combined x-ray and thermal conductivity study of hexagonal-close packed helium-4

Thermal conductivity measurements made on hexagonal-close-packed helium-4 are reported for specimens whose quality and orientation were determined directly by an x-ray method. The specimens, 2.2mmin diameter by 23 mm long, were held in a nylon container. They were obtained by unidirectional growth from the fluid at a constant pressure of 290 atmospheres and by recrystallization. Laue x-ray photographs taken over 17 mm of the total length proved to be a very sensitive indicator of specimen quality. These photographs showed specimens grown from the fluid in the nylon container to be of inferior quality to those obtained by recrystallization of samples rapidly grown from the fluid. The thermal conductivity was lower in the low temperature and the umklapp regimes for the specimens of inferior quality. The thermal conductivity was highest at all, temperatures for a single crystal obtained by recrystallization. This crystal was oriented with the c-axis perpendicular to the axis of the specimen and of the heat current. The thermal conductivityKfor this specimen could be represented at higher temperatures by the :equation K = A exp (9 /bT), where A = o L 1 X 10 -4 watts/ cm-deg, e = 58 K, b = 3.0, and T is the absolute temperature. This temperature dependence is the same as that observed in previous work at higher densities, but not at lower densities.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Fain, Samuel Clark, Jr.

Contributors dc:contributor

• Lazarus, David

• x-ray studies
• thermal conductivity
• hexagonal close packed helium-4
• laue x-ray photography

Statement dc:rights

• 1969 Samuel Clark Fain, Jr.

Language dc:language

en

Identifier

6072099

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25798