Oscillatory he II mass flow behaviour of feps in self sutained mode

Abstract

He II flow driven by Fountain effect pumps(FEPs) operating in self sustained mode in test loops of different impedances have shown oscillatory behaviour for test section heat loads upto 1.2W. The period of oscillation depends on the applied heat load, bath temperature of He II (Tbath) and the impedance of the test loop. The occurrence of oscillations is qualitatively understood due to the existence of an “onset temperature” to generate convection in the loop. The boundary between the stable and oscillatory states have been mapped. A combined normal and self sustained mode of operation of FEP eliminates these oscillations for practical applications.