Visualization study of the interface between superheated He II and superheated He I in a two-dimensional narrow channel by using the shadowgraph method

Dynamic behavior of superheated He II–superheated He I interface as a result of heating in a narrow channel between parallel walls that simulates cooling channels of superconducting magnets was investigated using a shadowgraph visualization method. It was confirmed that a superheated state could be created in the narrow channel without preparing a special calm environment. A superheated He II–superheated He I interface transiently appeared between 2.0 K and lambda temperature when applying a small heat flux. The boiling state accompanying the superheated He II–superheated He I interface was repeatedly generated and collapsed. This boiling mode was anticipated to have a high heat transfer coefficient.