Development of a ³He-hydraulic actuator for spin pump in superfluid ³He-A₁

The superfluid ³He A₁ phase contains a spin-polarized condensate. This property allows novel superfluid spin current experiments. In the mechano-spin effect of the A₁ phase a mechanically applied pressure gradient and a superleak-spin filter enable to directly boost spin polarization of ³He in a small chamber. Using a flexible membrane as an electrostatically actuated pump, we carried out such experiments and observed 50% enhancement of spin density. Here we report on a new ³He- hydraulic actuator for achieving greater enhancement of spin density. The actuator consists of two liquid ³He chambers located at a 4.2 K plate and in the interior of the cell. The pressure in the 4.2 K chamber is heater-controlled and it transmits a force onto a membrane in the cell. The motion of the membrane induces spin-polarized current into an accumulation chamber.