Abstract
Measurements of the efficiency of electromagnetic detection and generation of ultrasonic shear waves in superconducting tin are presented. Theoretical calculations of the generation efficiency are given, based upon a model by Quinn. Similar calculations are made for the radiation (detection) efficiency by adapting the Pippard model for ultrasonic shear wave attenuation, and lead to an identical temperature dependence as that predicted for the generation efficiency. Excellent agreement with this predicted behavior is found for experimental observations of the radiation efficiency for an electropolished (001) surface in tin at 15.3 MHz, using a single adjustable parameter. This parameter corresponds to a value of the London penetration depth lambda/sub L/(0) = 253 +- 25 A, in agreement with values found in the literature. The experimental generation efficiency is found to be strongly power dependent and is described theoretically by adapting the theory to the case of the intermediate superconducting state established at the surface by the rf magnetic field. Experimental radiation efficiencies are also found to be very sensitive to surface damage, a fact which is attributed to collision drag of the electrons by the lattice in the damaged layer. The theory, modified to allow for surface damage, gives reasonable agreement withmore » experimental radiation efficiencies for etched and spark-planed surfaces. (AIP)« less
Published Version
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