Measurements of the critical velocity of hydraulic cavitation in superfluid 4He

Abstract

In an effort to clarify the mechanism of the inception of phase transition in liquid helium, He II was made cavitate in the flow through a glass-constriction-nozzle with a diameter of 0.45 mm by using a fountain effect pump. Attainable critical velocities for incipient cavitation were obtained over a temperature range of 1.2 K to λ-point. It was found that the cavitation threshold observed was quite low, with an approximate range of 0.1 KPa to approximately -1 KPa. The result seems to show that, contrary to the hypothesis of nuclear bubbles, some kind of direct coupling between the state of flow of He II, probably superfluid turbulence, and the inception of cavitation may be blamed for the phenomena.