202 research outputs found
Dynamic positive column in long-gap barrier discharges
A simple analytical model of the barrier discharge in a long gap between
opposing plane electrodes is developed. It is shown that the plasma density
becomes uniform over large part of the gap in the course of the discharge
development, so that one can speak of a formation of a dynamic positive column.
The column completely controls the dynamics of the barrier discharge and
determines such characteristics as the discharge current, discharge duration,
light output, etc. Using the proposed model, all discharge parameters can be
easily evaluatedComment: 7 pages, 8 figures; submitted to the Journal of Applied Physic
Collective Sideband Cooling in an Optical Ring Cavity
We propose a cavity based laser cooling and trapping scheme, providing tight
confinement and cooling to very low temperatures, without degradation at high
particle densities. A bidirectionally pumped ring cavity builds up a resonantly
enhanced optical standing wave which acts to confine polarizable particles in
deep potential wells. The particle localization yields a coupling of the
degenerate travelling wave modes via coherent photon redistribution. This
induces a splitting of the cavity resonances with a high frequency component,
that is tuned to the anti-Stokes Raman sideband of the particles oscillating in
the potential wells, yielding cooling due to excess anti-Stokes scattering.
Tight confinement in the optical lattice together with the prediction, that
more than 50% of the trapped particles can be cooled into the motional ground
state, promise high phase space densities.Comment: 4 pages, 1 figur
Scattering of acoustic waves bubbles of gas in reservoirs
The article is concerned with questions of acoustic wave scattering by gas bubbles. The results obtained allow determining the acoustic resonant frequency, in which the effect of oil-producing formation wave treatment with gas bubbles is maximum
Thermobaric Effect on Melt-Textured MBaCuO (M = Y, Nd)
The effect of a short (10-30 min) thermobaric action (in the 1-5 GPa pressure
and 700-1300C temperature range) on the structure, superconductive and
mechanical properties of melt-textured-MBaCuO (M=Y, Nd) or
MT-MBCO have been studied. The existence has been established of
pressure-temperature--time conditions (2 GPa, 800C for 30 min and
900-950C for 15 min for MT-YBCO; 5 GPa, 850-900C for 15 min for
MT-NdBCO) the treatment under which allows superconductive properties of the
materials (because of the contact with zirconia and high pressure) to be
preserved or improved, mechanical characteristics increased and the materials
condensed.Comment: 2 pages (tex), 2 figures (eps), to be presented at LT2
Development of a Li2MoO4 scintillating bolometer for low background physics
We present the performance of a 33 g Li2MoO4 crystal working as a
scintillating bolometer. The crystal was tested for more than 400 h in a
dilution refrigerator installed in the underground laboratory of Laboratori
Nazionali del Gran Sasso (Italy). This compound shows promising features in the
frame of neutron detection, dark matter search (solar axions) and neutrinoless
double-beta decay physics. Low temperature scintillating properties were
investigated by means of different alpha, beta/gamma and neutron sources, and
for the first time the Light Yield for different types of interacting particle
is estimated. The detector shows great ability of tagging fast neutron
interactions and high intrinsic radiopurity levels (< 90 \muBq/kg for 238-U and
< 110 \muBq/kg for 232-Th).Comment: revised versio
- …