Phonons thermal, imaging

In order to image the interaction of phonons with internal structure in a specimen, scattering by thermal phonons can be used to attenuate the acoustic beam in a cryogenic microscope (Foster 1984). Experiments to test this confirmed that the cryogenic microscope was indeed able to detect on one surface of a sapphire disc the arrival of thermal phonons generated by a... 

Fig. 3.5. Thermal phonon imaging, 4.2 GHz. (a) Direct acoustic micrograph (b) heater pulsed synchronously with acoustic microscope (c) the second picture divided by the first (Foster and Rugar 1985).

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