Second sound shock waves and critical velocities in liquid helium II

Citation

Turner, Timothy Neal (1980) Second sound shock waves and critical velocities in liquid helium II. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/cg05-6436. https://resolver.caltech.edu/CaltechETD:etd-10132006-075044

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

Large amplitude second-sound shock waves have been generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound shock fronts is calculated and compared to experimental data. Theoretically it is shown that at T = 1.88°K, where the nonlinear wave steepening vanishes, the thickness of a very weak shock must diverge. In a region near this temperature, a finite-amplitude shock pulse will evolve into an unusual double-shock configuration consisting of a front steepened, temperature raising shock followed by a temperature lowering shock. Double-shocks are experimentally verified. The theoretical dependence of the shock induce temperature jump on the Mach number is successfully verified for large amplitudes ([...]) after the response of a thin-film superconducting temperature sensor is analyzed.

The ability of second-sound shock waves to simultaneously produce and measure very large relative velocities in regions away from the disruptive influence of walls makes them an invaluable tool in the study of critical velocities intrinsic to the fluid. It was experimentally discovered that very large second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically displayed as a limit to the maximum attainable shock strength. Although the observed breakdown could not be definitely attributed to a critical velocity, the value of the maximum shock-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium II. The observed limits within which superfluidity was still maintained (w=3.67 m/sec at T = 1.45°K, and w = 3.20 m/sec at T = 1.85°K) are the largest counterflow velocities ever obtained outside of restricted geometries.

Thesis Files