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The scattering of ultrasonic third sound from substrate surface defects |
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| Authors: | Edward R Generazio Robert W Reed |
| Affiliation: | (1) Department of Physics and Applied Research Laboratory, Pennsylvania State University, University Park, Pennsylvania;(2) Present address: National Aeronautic and Space Administration, Lewis Research Center, Cleveland, Ohio;(3) Present address: United Technologies Research Center, East Hartford, Connecticut |
| Abstract: | The interaction of third sound with isolated surface defects is examined. Phase-inverted reflections are observed to occur at surface defects even when the wavelength of the third sound is much greater than the dimensions of the defect. The origin of the scattering mechanism is believed to be due to the change in the helium film thickness in the vicinity of the topological variations introduced by the presence of the surface defects. Data are obtained for ultrasonic frequencies in the 20–200 kHz range. |
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