Study of standard thermometers and their reproduction of the λ point in liquid helium

1999 ◽  
Vol 42 (7) ◽  
pp. 689-692 ◽  
Author(s):  
D. N. Astrov ◽  
S. V. Korostin
Keyword(s):  
Liquid Helium ◽  
Λ Point

NON-CLASSICAL FILM FREE CONVECTION IN SUPERFLUID LIQUID HELIUM II NEAR THE λ-POINT

1974 ◽  
Author(s):  
R. C. Amar ◽  
S. C. Soloski ◽  
Traugott H. K. Frederking
Keyword(s):  
Free Convection ◽  
Liquid Helium ◽  
Helium Ii ◽  
Λ Point

Thermal Emission of Electrons from Liquid Helium

1971 ◽  
Vol 26 (9) ◽  
pp. 1392-1397 ◽  
Author(s):  
W . Schoepe ◽  
G . W . Rayfield
Keyword(s):  
Free Surface ◽  
Liquid Helium ◽  
Energy Barrier ◽  
Thermal Emission ◽  
Escape Rate ◽  
Potential Well ◽  
Vapor Interface ◽  
Smoluchowski’S Equation ◽  
Λ Point ◽  
Liquid Vapor

Abstract The free surface of liquid helium acts as an energy barrier for electrons crossing the surface from the liquid into the vapor. The barrier is shown to be induced by the dielectric image-potential acting on the electrons below the liquid vapor interface. The application of an extracting electric field across the surface reduces the barrier and leads to a potential well below the surface which traps the electrons for extended periods of time. The escape into the vapor phase is shown to be dominated by thermal diffusion from the potential well according to Smoluchowski's equation. By measuring the escape rate a barrier height of 43.8 ± 0.7 K has been found. The top of the well lies 25 Å below the liquid vapor interface. Close to the λ-point and at higher temperatures the escape rate deviates from the theory. The relevancy of the present work for previous and further investigations of thermal eelctron emission from liquid helium is discussed.

Kapitza resistance of cerium ethylsulphate

1968 ◽  
Vol 46 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Hans Glättli
Keyword(s):  
Magnetic Field ◽  
Liquid Helium ◽  
Spin System ◽  
Energy Transport ◽  
Relaxation Times ◽  
Bath Temperature ◽  
Limiting Factor ◽  
Kapitza Resistance ◽  
Experimental Values ◽  
Λ Point

Spin–bath relaxation times τ of cerium ethylsulphate (CeES) immersed in liquid helium have been measured at magnetic fields up to 6 kOe. The electronic spin system of CeES has been heated by pulsed microwave radiation and the return to the equilibrium bath temperature has been monitored, using the optical Faraday rotation. At temperatures below the λ point of liquid helium, τ is a few ms and weakly dependent on magnetic field and temperature. It is assumed that the Kapitza boundary resistance Rk is the limiting factor in the energy transport between the spin system of CeES and the surrounding liquid helium. This assumption is supported by measurements of τ above the λ point between CeES and liquid or gaseous helium. Rk has been calculated from the experimental values of τ using a simple thermodynamical model. The resulting temperature dependence can be fitted with the expression Rk = 30 T−2.4 cm2 °K s (joule)−1 independent of magnetic field. The same model has been applied to PrES, which has been shown previously to exhibit a similar relaxation behavior. The results of Rk are close to those obtained for CeES.

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