We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed inside porous glasses during the process of helium condensation. The context, aims, and results of these experiments are reviewed, with focus on the specificity...

We study two techniques to create electrons in a liquid helium environment. One is thermionic emission of tungsten filaments in a low temperature cell in the vapor phase with a superfluid helium film covering all surfaces; the other is operating a glowing filament immersed in bulk liquid helium. We present both the steady state and rapid sweep I-V curves and the electron current yield. These cu...

For bulk liquid helium the bottom of the conduction band (V0) is above the vacuum level. In this case the surface of the liquid represents an electronic surface barrier for an electron to be injected into the liquid. Here we study the electronic conduction band for doped helium droplets of different sizes. Utilizing an electron monochromator, the onset of the (H2O)2- ion yield corresponding to ...

© 2009 American Institute of Physics, S-0031-9228-0910-020-0 Early research with liquid helium showed that it had remarkable new properties, especially below the so-called lambda transition near 2.2 K, where there is a sharp, narrow peak in the specific heat (see figure 1a). The liquid below the transition was named helium II to distinguish it from the liquid above the transition, called helium...

This article describes an accurate subPico flowmeter bifurcatedin to liquid and gas flowrates less than 1mol/s for both MEMS/NEMS and cryogenic technology applications. The MEMS/NEMS are described as either two Gauges (instrument), or quartz fluctuating forks, even if the liquid or gas flows through an element, as well as cryogenic technology consisting of arrays of e...

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Juho Rysti Name of the doctoral dissertation Microscopic and Macroscopic Studies of Liquid and Solid Helium Mixtures Publisher School of Science Unit O.V. Lounasmaa Laboratory Series Aalto University publication series DOCTORAL DISSERTATIONS 110/2013 Field of research Engineering Physics, Physics Manuscript submitted 16 April ...

By focusing a high-intensity acoustic wave in liquid helium, we have observed the nucleation of solid helium inside the wave above a certain threshold in amplitude. The nucleation is a stochastic phenomenon. Its probability increases continuously from 0 to 1 in a narrow pressure interval around P(m) + 4.7 bars ( P(m) = 25.3 bars is the melting pressure where liquid and solid helium are in equil...

This article describes an accurate subPico flowmeter bifurcatedin to liquid and gas flowrates less than 1mol/s for both MEMS/NEMS and cryogenic technology applications. The MEMS/NEMS are described as either two Gauges (instrument), or quartz fluctuating forks, even if the liquid or gas flows through an element, as well as cryogenic technology consisting of arrays of e...

Using frozen hydrogen particles to observe rotating and quantized flows in liquid helium Gregory P. Bewley 2006 We present a novel technique for tracing liquid helium flows, and use this technique to make observations of fluid dynamics in both the normal fluid and the superfluid phases of liquid helium. To visualize fluid motions, we create a suspension of frozen hydrogen particles with diamete...

The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concep...