PHONON INTERACTIONS IN CRYSTALS.

The purpose of this contract is to investigate various interaction processes of phonons in solids with a view towards developing and improving methods of amplifying, generating, frequency converting, and propagating microwave acoustic energy. A chief approach is to study the parametric amplification and parametric frequency conversion of acoustic waves, especially the forward travelling wave interaction. The use of paramagnetic ions in magnesium oxide is being investigated to maximize such effects. Since the phase velocity of an acoustic wave of a specific frequency can be changed by resonating the paramagnetic ion, advantage can be taken of various constructive and destructive interference effects to enhance these travelling wave parametric mixing effects. Microwave acoustic masers and electron - phonon interaction effects are also being studied for the same reasons.