Visualization of selected flows of superfluid helium using solid hydrogen tracer particles

Daniel Duda Visualization of selected flows of superfluid helium using solid hydrogen tracer particles 5 Thesis title: Visualization of selected flows of superfluid helium using solid hydrogen tracer particles Author: Bc. Daniel Duda Department: Department of Low Temperature Physics, Supervisor: prof. RNDr. Ladislav Skrbek, DrSc, Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University in Prague. Consultant: Dr. Marco La Mantia, PhD. Abstract: Quantum turbulence generated in thermal counterflow of He II is studied experimentally by visualization. The statistical properties of the motion of micron size solid deuterium particles are studied by using the particle tracking velocimetry technique at length scales comparable to the mean distance between quantized vorti- ces. The probability density function (PDF) of the longitudinal velocity displays two peaks that correspond to two velocity fields of the two-fluid description of He II. The PDF of the transversal velocity displays a classical-like Gaussian core with non- classical power-law tails, confirming the quantum nature of turbulence in counter- flowing He II. The distribution of the particle acceleration is found to be similar in shape to the classical one, in the range of investigated parameters. The observed de-..