230 research outputs found
Functional birefringent elements imprinted by femtosecond laser nanostructuring of multi-component glass
A decade ago, a new type of self-organization process was observed in the bulk of SiO2 glass after irradiation with ultrashort laser pulses [1]. Under certain irradiation conditions, highly ordered nanostructures with features smaller than 20 nm could be formed in the irradiated volume. The sub-wavelength arrangement of these structures results in form birefringence, which was recently exploited for demonstrating a variety of functional optical elements in silica glass [2]. Despite excellent physical and chemical properties of fused silica, the applications of this glass are limited due to the expensive manufacturing process associated with high melting temperature. Recently the evidence of laser-induced nanogratings in glasses other than SiO2 was reported, including GeO2 glass [3], binary titanium silicate glass (ULE, Corning) and multicomponent borosilicate glass (Borofloat 33, Schott) [4]. However, birefringence induced in borosilicate glass was more than one order of magnitude lower than in pure SiO2 glass
Plasma focus installation as a tool for the study of the interaction of high power plasma streams with condensed matter
In this work the possibilities of the use of the high-current discharges of Plasma Focus type for the investigation of
the effect of plasma on the materials are discussed. From this point of view the properties of plasma streams and ion
beams arising in the PF discharges are studied. Here, as an example of an application of the Plasma Focus device (PF),
we studied the influence on Vanadium (perspective material in nuclear power engineering) a cumulative streams
producing in the P
Quark and pion condensation in a chromomagnetic background field
The general features of quark and pion condensation in dense quark matter
with flavor asymmetry have been considered at finite temperature in the
presence of a chromomagnetic background field modelling the gluon condensate.
In particular, pion condensation in the case of a constant abelian
chromomagnetic field and zero temperature has been studied both analytically
and numerically. Under the influence of the chromomagnetic background field the
effective potential of the system is found to have a global minimum for a
finite pion condensate even for small values of the effective quark coupling
constant. In the strong field limit, an effective dimensional reduction has
been found to take place.Comment: 17 pages, 6 figure
Modulation of microwave radiation in the process of resonant interaction with a counter-propagating rectilinear electron beam
Measurement of the nuclear multiplicity ratio for hadronization at CLAS
The influence of cold nuclear matter on lepto-production of hadrons in
semi-inclusive deep inelastic scattering is measured using the CLAS detector in
Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the
multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a
function of the fractional virtual photon energy transferred to the
and the transverse momentum squared of the . We find that the
multiplicity ratios for are reduced in the nuclear medium at high
and low , with a trend for the transverse momentum to be
broadened in the nucleus for large .Comment: Submitted to Phys. Lett.
Demonstration of a novel technique to measure two-photon exchange effects in elastic scattering
The discrepancy between proton electromagnetic form factors extracted using
unpolarized and polarized scattering data is believed to be a consequence of
two-photon exchange (TPE) effects. However, the calculations of TPE corrections
have significant model dependence, and there is limited direct experimental
evidence for such corrections. We present the results of a new experimental
technique for making direct comparisons, which has the potential to
make precise measurements over a broad range in and scattering angles. We
use the Jefferson Lab electron beam and the Hall B photon tagger to generate a
clean but untagged photon beam. The photon beam impinges on a converter foil to
generate a mixed beam of electrons, positrons, and photons. A chicane is used
to separate and recombine the electron and positron beams while the photon beam
is stopped by a photon blocker. This provides a combined electron and positron
beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen
target. The large acceptance CLAS detector is used to identify and reconstruct
elastic scattering events, determining both the initial lepton energy and the
sign of the scattered lepton. The data were collected in two days with a
primary electron beam energy of only 3.3 GeV, limiting the data from this run
to smaller values of and scattering angle. Nonetheless, this measurement
yields a data sample for with statistics comparable to those of the
best previous measurements. We have shown that we can cleanly identify elastic
scattering events and correct for the difference in acceptance for electron and
positron scattering. The final ratio of positron to electron scattering:
for GeV and
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
Cross-Correlation Earthquake Precursors in the Hydrogeochemical and Geoacoustic Signals for the Kamchatka Peninsula
We propose a new type of earthquake precursor based on the analysis of
correlation dynamics between geophysical signals of different nature. The
precursor is found using a two-parameter cross-correlation function introduced
within the framework of flicker-noise spectroscopy, a general statistical
physics approach to the analysis of time series. We consider an example of
cross-correlation analysis for water salinity time series, an integral
characteristic of the chemical composition of groundwater, and geoacoustic
emissions recorded at the G-1 borehole on the Kamchatka peninsula in the time
frame from 2001 to 2003, which is characterized by a sequence of three groups
of significant seismic events. We found that cross-correlation precursors took
place 27, 31, and 35 days ahead of the strongest earthquakes for each group of
seismic events, respectively. At the same time, precursory anomalies in the
signals themselves were observed only in the geoacoustic emissions for one
group of earthquakes.Comment: 21 pages, 5 figures, 1 table; to be published in "Acta Geophysica".
arXiv admin note: substantial text overlap with arXiv:1101.147
Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
Several recent advances in turbulent dynamo theory are reviewed. High
resolution simulations of small-scale and large-scale dynamo action in periodic
domains are compared with each other and contrasted with similar results at low
magnetic Prandtl numbers. It is argued that all the different cases show
similarities at intermediate length scales. On the other hand, in the presence
of helicity of the turbulence, power develops on large scales, which is not
present in non-helical small-scale turbulent dynamos. At small length scales,
differences occur in connection with the dissipation cutoff scales associated
with the respective value of the magnetic Prandtl number. These differences are
found to be independent of whether or not there is large-scale dynamo action.
However, large-scale dynamos in homogeneous systems are shown to suffer from
resistive slow-down even at intermediate length scales. The results from
simulations are connected to mean field theory and its applications. Recent
work on helicity fluxes to alleviate large-scale dynamo quenching, shear
dynamos, nonlocal effects and magnetic structures from strong density
stratification are highlighted. Several insights which arise from analytic
considerations of small-scale dynamos are discussed.Comment: 36 pages, 11 figures, Spa. Sci. Rev., submitted to the special issue
"Magnetism in the Universe" (ed. A. Balogh
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