Periodic Oscillation of Liquid Helium Boiling in a Narrow Rectangular Duct

Temperature fluctuations in saturated superfluid He II (at 1.9 K) were measured using small thermistors operated by a lock-in amplifier. The experiments were performed in a rectangular channel (13×13×200mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$13\times 13\times 200~\hbox {mm}$$\end{document}) with a heater set at the bottom. The temperature oscillated periodically, and a pulsive boiling sound appeared. The two become synchronized, and the oscillating frequencies strongly depend on the helium pressure and the heat flux. When the He pressure decreases, the oscillation frequency decreases. A simple model to predict the cyclic period is presented.