Pressure Driven 3He Flow Through Submicron Sized Apertures

摘要

The flow of liquid 3He through different weak link structures was investigated at temperatures of 1 mK to 1 K and at pressures ≈0 bar by measuring the characteristic time τ which was needed for pressure equilibration between two volumes connected by the weak link. Two types of weak links were used, one with a regular structure of 65×65 holes of 150 nm diameter in a 50 nm thick SiN membrane, and another with 105 holes of 15 nm diameter statistically distributed over a 14 nm thick nitrocellulose film. For the flow through the 150 nm holes the expected transition from Knudsen flow at low T to viscous flow at high T was observed. To the contrary, the normal fluid 3He-flow through the 15 nm structure does not show any temperature dependence. The relaxation time τ dropped by orders of magnitude for both types of weak links below the superfluid transition.