215 research outputs found
Novel Scintillation Material - ZnO Transparent Ceramics
ZnO-based scintillation ceramics for application in HENPA LENPA analyzers
have been investigated. The following ceramic samples have been prepared:
undoped ones (ZnO), an excess of zinc in stoichiometry (ZnO:Zn), doped with
gallium (ZnO:Ga) and lithium (ZnO:Li). Optical transmission, x-ray excited
emission, scintillation decay and pulse height spectra were measured and
analyzed. Ceramics have reasonable transparency in visible range (up to 60% for
0.4 mm thickness) and energy resolution (14.9% at 662 keV Cs137 gamma
excitation). Undoped ZnO shows slow (1.6 {\mu}s) luminescence with maximum at
2.37 eV and light yield about 57% of CsI:Tl. ZnO:Ga ceramics show relatively
low light yield with ultra fast decay time (1 ns). Lithium doped ceramics
ZnO:Li have better decay time than undoped ZnO with fair light yield. ZnO:Li
ceramics show good characteristics under alpha-particle excitation and can be
applied for the neutral particle analyzers.Comment: 4 pages, 8 figures, research covered in this paper was presented at
SCINT2011 conference as a poster, submitted for publication at IEEE Trans.
Nucl. Sc
Ab initio study of the vapour-liquid critical point of a symmetrical binary fluid mixture
A microscopic approach to the investigation of the behaviour of a symmetrical
binary fluid mixture in the vicinity of the vapour-liquid critical point is
proposed. It is shown that the problem can be reduced to the calculation of the
partition function of a 3D Ising model in an external field. For a square-well
symmetrical binary mixture we calculate the parameters of the critical point as
functions of the microscopic parameter r measuring the relative strength of
interactions between the particles of dissimilar and similar species. The
calculations are performed at intermediate () and moderately long
() intermolecular potential ranges. The obtained results agree
well with the ones of computer simulations.Comment: 14 pages, Latex2e, 5 eps-figures included, submitted to
J.Phys:Cond.Ma
Thermodynamic characteristics of the classical n-vector magnetic model in three dimensions
The method of calculating the free energy and thermodynamic characteristics
of the classical n-vector three-dimensional (3D) magnetic model at the
microscopic level without any adjustable parameters is proposed. Mathematical
description is perfomed using the collective variables (CV) method in the
framework of the model approximation. The exponentially decreasing
function of the distance between the particles situated at the N sites of a
simple cubic lattice is used as the interaction potential. Explicit and
rigorous analytical expressions for entropy,internal energy, specific heat near
the phase transition point as functions of the temperature are obtained. The
dependence of the amplitudes of the thermodynamic characteristics of the system
for and on the microscopic parameters of the interaction
potential are studied for the cases and . The obtained
results provide the basis for accurate analysis of the critical behaviour in
three dimensions including the nonuniversal characteristics of the system.Comment: 25 pages, 5 figure
A Model for the Production of Regular Fluorescent Light from Coherently Driven Atoms
It has been shown in recent years that incoherent pumping through multiple
atomic levels provides a mechanism for the production of highly anti-bunched
light, and that as the number of incoherent steps is increased the light
becomes increasingly regular. We show that in a resonance fluorescence
situation, a multi-level atom may be multiply coherently driven so that the
fluorescent light is highly anti-bunched. We show that as the number of
coherently driven levels is increased, the spontaneous emissions may be made
increasingly more regular. We present a systematic method for designing the
level structure and driving required to produce highly anti-bunched light in
this manner for an arbitrary even number of levels.Comment: 6 pages multicol revtex, including figure
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