84 research outputs found
Measurement of the neutron electric dipole moment by crystal diffraction
An experiment using a prototype setup to search for the neutron electric
dipole moment by measuring spin-rotation in a non-centrosymmetric crystal
(quartz) was carried out to investigate statistical sensitivity and systematic
effects of the method. It has been demonstrated that the concept of the method
works. The preliminary result of the experiment is ecm. The experiment showed that an accuracy of ecm can be obtained in 100 days data taking, using available
quartz crystals and neutron beams.Comment: 13 pages, 4 figure
A quantum mechanical description of the experiment on the observation of gravitationally bound states
Quantum states in the Earth's gravitational field were observed, when
ultra-cold neutrons fall under gravity. The experimental results can be
described by the quantum mechanical scattering model as it is presented here.
We also discuss other geometries of the experimental setup which correspond to
the absence or the reversion of gravity. Since our quantum mechanical model
describes, particularly, the experimentally realized situation of reversed
gravity quantitatively, we can practically rule out alternative explanations of
the quantum states in terms of pure confinement effects.Comment: LaTeX, 10 pages, 4 figures, v2: references adde
Study of Compacting Methods for Nanostructured Thermoelectric Materials Based on Si-Ge and Half -Heusler Alloys
Recent methods of compacting nanopowders of thermoelectric materials of silicon germanium and
Half-Heusler (HH) compounds based on Ni(Ti,Zr,Hf)Sn are presented. Half-Heusler alloys are known to be
intermetallic compounds with quite large Seebeck coefficient and semiconducting transport properties.
This makes them a potential candidate for thermoelectric applications. In this study we compare compacting
methods applied to raw materials as a function of crystal structure. The results suggest that the thermal
conductivity can be reduced by increasing the phonon scattering via nanostructuring. The effect of
spark plasma sintering (SPS) and hot pressing on Gleeble system was analyzed by TEM and SEM methods.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3551
Thermoelectric Properties of Si-Ge Nanostructured Thermoelectric Materials Synthesized by Mechanical Alloying
Silicon-germanium alloys is one of the best thermoelectric materials in power generation devices operating
in 600-1000 C range in heat conversion into electricity directly. The enhancement of efficiency comes
mainly from a significant reduction in the thermal conductivity caused by the enhanced phonon scattering
off the increased density of nanograin boundaries.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3551
Constraints on spin-dependent short-range interactions using gravitational quantum levels of ultracold neutrons
In this paper, we discuss a possibility to improve constraints on
spin-dependent short-range interactions in the range of 1 - 200 micrometer
significantly. For such interactions, our constraints are without competition
at the moment. They were obtained through the observation of gravitationally
bound states of ultracold neutrons. We are going to improve these constraints
by about three orders of magnitude in a dedicated experiment with polarized
neutrons using the next-generation spectrometer GRANIT.Comment: 5 pages, 4 figures, accepted for publication in the Proceedings of
the International Workshop on Particle Physics with Cold Neutrons, Grenoble,
May 2008, to be published in Nucl. Instr. and Meth.
Measurement of the neutron electric dipole moment via spin rotation in a non-centrosymmetric crystal
We have measured the neutron electric dipole moment using spin rotation in a
non-centrosymmetric crystal. Our result is d_n = (2.5 +- 6.5(stat) +-
5.5(syst)) 10^{-24} e cm. The dominating contribution to the systematic
uncertainty is statistical in nature and will reduce with improved statistics.
The statistical sensitivity can be increased to 2 10^{-26} e cm in 100 days
data taking with an improved setup. We state technical requirements for a
systematic uncertainty at the same level.Comment: submitted to Phys. Lett.
A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer
We present a method to measure the resonance transitions between the
gravitationally bound quantum states of neutrons in the GRANIT spectrometer.
The purpose of GRANIT is to improve the accuracy of measurement of the quantum
states parameters by several orders of magnitude, taking advantage of long
storage of Ultracold neutrons at specula trajectories. The transitions could be
excited using a periodic spatial variation of a magnetic field gradient. If the
frequency of such a perturbation (in the frame of a moving neutron) coincides
with a resonance frequency defined by the energy difference of two quantum
states, the transition probability will sharply increase. The GRANIT experiment
is motivated by searches for short-range interactions (in particular
spin-dependent interactions), by studying the interaction of a quantum system
with a gravitational field, by searches for extensions of the Standard model,
by the unique possibility to check the equivalence principle for an object in a
quantum state and by studying various quantum optics phenomena
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