Third-sound attenuation and reflection for a He-4 film in a cesium corral

In a previous paper we reported the construction of a two-dimensional third -sound resonator with Cs boundaries on a polymethyl-methacrylate (PMMA) coa ted substrate and preliminary observations of the behavior of third sound i nside the resonator [J. C. Herrmann and R. B. Hallock, J. Low Temp. Phys. 1 10, 671 (1998)]. Under the appropriate conditions, the Cs boundaries act as nonwet edges, effectively confining the He-4 to the region enclosed by the Cs and causing third sound to be reflected at the boundaries. After a brie f sketch of the resonator's construction, we present a more extensive analy sis of third sound within the resonator and the results of third-sound atte nuation and Cs boundary reflection measurements made in the resonator for a ll 4He coverages we studied. In addition we include the results of a compan ion experiment in which we verify the ''normal'' propagation of third sound on PMMA. [S0163-1829(99)04902-4].