Superfluid Vorticity and I / f Noise in Mlting of Solid 4 He

One of the ways to reach a zero-vorticity state in superfluid 4He is to melt solid helium slowly at temperatures well below T\. This method takes advantage of the small density difference between the liquid and solid phases and of the high critical velocities for vortex formation at low T. However, pinning of the liquid-solid interface on the walls, revealed by I/f-like pressure fluctuations of up to 1-10 pbar in our setup, has consistently led to remanent vortex line densities of ~ 4 . 103 lines per cm2. PACS numbers: 67.40V 68.45