Phonon Scattering by Isolated Isotopic Impurities in Single Crystals of Helium

Thermal conductivity measurements of oriented single crystals of hexagonal close-packed He4 have been made in order to study the scattering of phonons by isotopic impurities. Apparatus and techniques have been developed which allow the growth of crystals at preferred orientations: c-axis orientation...

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Bibliographic Details
Main Author: Lawson,Dewey Tull
Format: Report
Language:English
Subjects:
CRYOGENICS
CRYSTAL GROWTH
EXPERIMENTAL DESIGN
HELIUM
HELIUM 4
HEXAGONAL CLOSE PACKED CRYSTAL LATTICES
IMPURITIES
LATTICE THERMAL CONDUCTIVITY
PHONON SCATTERING
PHONONS
SCATTERING
SINGLE CRYSTALS
Solid State Physics
SOLIDIFIED GASES
TEST EQUIPMENT
THERMAL CONDUCTIVITY
THESES
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Summary:Thermal conductivity measurements of oriented single crystals of hexagonal close-packed He4 have been made in order to study the scattering of phonons by isotopic impurities. Apparatus and techniques have been developed which allow the growth of crystals at preferred orientations: c-axis orientations of 0 and 90 degrees with respect to the direction of heat flow were chosen for this study. Quality and orientation of the sample crystals were determined from the thermal conductivity measurements themselves. (Author)