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Title:Combined x-ray and thermal conductivity study of hexagonal-close packed helium-4
Author(s):Fain, Samuel Clark, Jr.
Doctoral Committee Chair(s):Lazarus, David
Department / Program:Physics
Subject(s):x-ray studies
thermal conductivity
hexagonal close packed helium-4
laue x-ray photography
Abstract: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.
Issue Date:1969
Genre:Dissertation / Thesis
Rights Information:1969 Samuel Clark Fain, Jr.
Date Available in IDEALS:2011-07-13
Identifier in Online Catalog:6072099

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