PHONON INTERACTIONS IN CRYSTALS.
Quarterly progress rept. no. 3, 15 Nov 63-14 Feb 64
IBM WATSON RESEARCH CENTER YORKTOWN HEIGHTS N Y
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Experimental work is summarized on the measurement of the signal velocity of acoustic waves in an amplifying acoustic maser. Theory and experiment have previously shown that the signal velocity is decreased when the acoustic waves can interact with absorbing paramagnetic ions. Theory indicates a similar decrease even if the spin populations are inverted so that the ions are emitting. Experimental results at present indicate on the contrary that the signal velocity remains either unchanged or is increased in an amplifying acoustic maser. The temperature dependence of the attenuation of 9 Gc acoustic waves was measured in a number of materials. These materials include magnesium oxide, silicon, germanium, quartz, sapphire, and calcium fluoride. It appears that there exists considerable similarity in the behavior of these various materials when account is taken solely of their Debye temperatures or, alternatively, of their acoustic velocities. Improvements of an experimental nature were made on the germanium samples to be used in a phonon amplification experiment. Author