We present design details and test results for the first short-term frequency standard to achieve ultra-high stability (oy < without he use of liquid helium. Technical features include vibration isolation by atmospheric helium gas and a new sapphire resonator design with adjustable compensation operating at 8-10K.

Positively charged helium droplets were produced by ionization of liquid helium in an electrostatic spraying experiment, in which fluid emerging from a thin glass capillary was ionized by applying a high voltage to a needle inside the capillary. At 2.2 K, fine droplets (<10 μm in diameter) were produced in pulsed sprays or showers with total currents as high as 0.4 μA at relatively low voltages...

A review is given of the scattering of light by superfluid helium. A brief discussion is given first of the theory of Brillouin and Rayleigh scattering from an ordinary simple pure liquid. It is shown how this discussion must be modified in the case of the superfluid phase of purc 4He, and experimental observations of Brillouin scattering from first sound in liquid helium are described. The dis...

Hydrogen and helium are the most abundant elements in the Universe. They are also, in principle, the most simple. Nonetheless, they display remarkable properties under extreme conditions of pressure and temperature that have fascinated theoreticians and experimentalists for over a century. Advances in computational methods have made it possible to elucidate ever more of their properties. Some o...

We have developed an apparatus which can be used to monitor the motion of individual electrons in liquid helium. A sound wave is used to explode an electron bubble for a fraction of a microsecond. While the bubble is expanded, it is illuminated by light from a flash lamp. We describe the details of the experiment and show the results we obtained. The phononroton in liquid helium drags the elect...

The paper describes experiments with various superconducting type II cables and hollow conductor configurations, current distribution, size effect in superconductor and performance of multistranded superconducting stabilized cables and magnets. A 30 cm bore 70 kG split coil magnet with a total field energy of about 6 X lo6 joules currently being built at SLAC is presented and a new superconduct...

Two types of two-dimensional (2D) charged systems can appear near the free surface of liquid helium: surface electrons and surface ions [1]. The existence of these two systems has been predicted almost simultaneously (see Ref. [2] ). However, the electron variant of the problem has subsequently been investigated more thoroughly both theoretically and experimentally. The interest in 2D ion syste...

The flow of liquid helium through a single nanohole with radius smaller than 25 nm was studied. Mass flow was induced by applying a pressure difference of up to 1.4 bar across a 50 nm thick Si(3)N(4) membrane and was measured directly by means of mass spectrometry. In liquid He I, we experimentally show that the fluid is not clamped by the short pipe with diameter-to-length ratio D/L≃1, despite...

The recent discovery that silicon nitride membranes can be used as extremely high Q mechanical resonators makes possible a number of novel experiments, which include improved long range vacuum Casimir force measurements, and measurments of the properties of liquid helium below the lambda point. It is noted that in the thermal correction to the Casimir force, the phase velocity of the excitation...