Dynamic behavior of the He II-He I phase transition under gravity

The phase transition of superfluid helium (He II) to normal fluid helium (He I) is studied in this note. The He II-He I interface is found to move upwards under finite heat current. The temperature tracks are measured by four high resolution temperature sensors (HRTs). And the shifting of the λ point temperature (phase transition temperature) along the cell is studied experimentally and theoretically. Under gravity, the shifting of the λ point temperature increases with the pressure. The experimental results agree well with the theoretical ones.