CONSIDERATIONS ON MIXING CHAMBERS

Nous discutons quelques propriétés d'un système de boîtes à mélange. Le concept d'une boîte à mélange continu est introduit.Some of the experimental properties of a multiple mixing chamber are discussed. The concept of a continuous mixing chamber is introduced

Viscosity of saturated helium-3-helium-4 mixture below 200 mK

The shear viscosity of saturated3He-4He mixture has been measured at temperatures between 7 mK and 200 mK using a vibrating-wire viscometer and a calibrated pressure cell. The reliability of the vibrating-wire technique was tested by measuring the viscosity of pure4He. The results are internally consistent. A phenomenological expression is given for the viscosity of saturated3He-4He mixture between 7 mK and 80 mK

The high-field hall effect and magnetoresistance of electrons on helium

The diagonal and off-diagonal components of the resistivity tensor have been measured for the non-degenerate two-dimensional electron gas as a function of magnetic field. The Hall voltage varies linearly with the magnetic field, in fields up to the quantum limit. In contrast to the classical behaviour, a strong magnetoresistance is observed under quantising conditions. The observations are in agreement with the theoretically derived quantum transport magnetoresistivity tensor

Comprehensive theory of flow properties of 3He moving through superfluid 4He in capillaries

We propose a new set of hydrodynamic equations for flow of 3He through superfluid 4He. They differ from earlier work by including both a mutual friction force between 3He and 4He and a viscous force. Both the mechanical vacuum model, in which mutual friction is neglected, and an earlier model by the authors, without viscous force, are limiting cases of this new description. An experimental setup is devised in which both forces play a significant role. The results of this experiment are in agreement with the theory

3He flow in dilute 3He-4He mixtures at temperatures between 10 and 150 mK

The mutual friction between 3He and 4He II below 150 mK has been studied. Empirical relations for the adiabatic and the nonadiabatic flow properties of 3He moving through 4He have been determined using a dilution refrigerator with a single mixing chamber. The validity of the relations is verified by osmotic-pressure measurements and by measuring the properties of a double-mixing-chamber system. It is shown that superleak shunts have a strong effect on the flow characteristics. From the nonadiabatic flow properties an expression is derived for the mutual-friction-force density between 3He and 4He II. This has a strong resemblance to the Gorter-Mellink mutual-friction-force density between the normal and the superfluid components in pure 4He II. It is speculated that the 3He flow in our systems generates a 4He vortex tangle, which leads to the observed mutual friction between 3He and 4He and also to a strong clamping of the 4He to the walls

Thermodynamic properties of liquid 3He-4He mixtures at zero pressure for temperatures below 250 mK and 3He concentrations below 8%

We calculated the thermodynamic quantities of dilute liquid 3He-4He mixtures, starting from experimental values of the specific heat and the osmotic pressure. The calculations are confined to temperatures below 250 mK and 3He concentrations below 8% at zero pressure. Some results are especially useful for dilution refrigeration. Contrary to the calculations previously performed by Radebaugh, our results are in good agreement with the experimental date on both the osmotic pressure and the osmotic enthalpy