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A microfluidic vibrating wire viscometer for operation at high pressure and high temperature Rev. Sci. Instrum. 82, 035113 (2011);

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The osmotic pressure of Hes-He4 mixtures has been measured at temperatures 0.027-0. 65 K, for concentrations up to 10-mole % He, and for hydrostatic pressures of 0.26, 10, and 20 atm.The osmotic pressure was measured directly with a sensitive specially designed diaphragm pressure gauge. The temperatureand concentrationdependenceof the osmotic pressure is in fair agreement with the effective, interactiontheoryproposed by Bardeen, Baym, and Pines (BBP).It also agrees with a simple empirical model whichavoids the complicated calculations involved in obtaining the thermodynamic properties at finite tempexatures from the BBP theory. The model fits the temperature dependence of other thermodynamic properties of solutions. The osmotic pressure at absolute zero at 10 and 20 atm is used to determine the Hes effective mass and somewhat speculative values of the BBP quasiparticle interaction V(k) underpressure. The interaction under pressure is found to have a minimum at a nonzero value of k, and it may give rise to a "supermobile" transition at comparatively high temperatures.

= 3.5, y 0 = 2.5, and rc^SxlO 12 cm" 3 (i.e., al.3-MeV, 150-kA beam of 1.4 cm radius) and a hydrogen plasma of density n p~1 0 14 cm" 3 so that n B /n p x0.05.The final temperature is (T e +T { ) f «30 keV by Eq. (7) with/«y 0 /i/. The time required to achieve this temperature falls in the range 30 nsec<^ 0.5 K) demonstrates that some 3 He is adsorbed on the surface of the liquid. In Andreev's model the adsorbed 3 He is assumed to be in a set of independent quasiparticle states with energy spectrum 2 * = ~ € 0 +p 2 /2M.(1)The surface tension of the solution, a, is then the surface tension of liquid 4 He, a 4 , reduced by the two-dimensional "pressure" of the 3 He quasiparticle gas on the surface. From measurements of Aa=a 4~ a at T>0,5K and assuming that the sur-port No. . 7 Only a small drift of the ions t^{ m e /m i )vv p in the beam direction results from momentum conservation. 8 The factor d in Eq. (7) depends on the geometry and is given by d-\ +21n(b/a), where b is an outer radius where the field energy integral is cut off. 9 H. (to be published).face quasiparticle gas could be treated by Boltzmann statistics, Zinov'eva and Boldarev 3 determined approximate values for the surface binding energy e 0 and the effective mass M.There is considerable interest in studying the many-body properties of adsorbed helium particularly in this case since the substrate (liquid helium) is uniquely perfect and homogeneous. We therefore have made further measurements of a down to low temperatures (0.04 K) and over a wide range of X, the concentration in the bulk phase (30 ppm to saturation). Under these conditions the adsorbed 3 He can be changed from a fraction of an atomic layer, when it behaves like Some properties of 3 He adsorbed on the surface of liquid helium are determined from measurements of the surface and interfacial tension of 3 He-4 He mixtures. As a mixture approaches phase separation, the 3 He adsorbed on the surface grows continuously into the upper, 3 He-rich phase. At all temperatures the limit of low surface density is well described by the Andreev model, although there is some evidence for a weak, attractive quasiparticl...