930 research outputs found
Piecewise acceleration of electrons across a periodic solid-state structure irradiated by intense laser pulse
Three-dimensional particle-in-cell simulations show that the periodic
solid-state structures irradiated by intense ( W/cm) laser
pulses can generate collimated electron bunches with energies up to 30 MeV (and
acceleration gradient of GeV/cm), if the microstructure period is equal
to the laser wavelength. A one-dimensional model of piecewise acceleration in
the microstructure is proposed and it is in a good agreement with the results
of numerical simulations. It shows that the acceleration process for
relativistic electrons can be theoretically infinite. In the simulations, the
optimal target parameters (the width of the microstructure elements and the
microstructure period) are determined. The explored parameters can be used for
proof-of-principle experiments demonstrating an ultrahigh gradient acceleration
by a number of identical and mutually coherent laser pulses [A. Pukhov et al.,
Eur. Phys. J. Spec. Top. 223, 1197 (2014)]
Theory of the collapsing axisymmetric cavity
We investigate the collapse of an axisymmetric cavity or bubble inside a
fluid of small viscosity, like water. Any effects of the gas inside the cavity
as well as of the fluid viscosity are neglected. Using a slender-body
description, we show that the minimum radius of the cavity scales like , where is the time from collapse. The exponent
very slowly approaches a universal value according to . Thus, as observed in a number of recent experiments, the
scaling can easily be interpreted as evidence of a single non-trivial scaling
exponent. Our predictions are confirmed by numerical simulations
Analytical description of the time-over-threshold method based on the time properties of plastic scintillators equipped with silicon photomultipliers
A new high-granular compact time-of-flight neutron detector for the
identification and energy measurement of neutrons produced in nucleus-nucleus
interactions at the BM@N experiment, Dubna, Russia, at energies up to 4 AGeV is
under development. The detector consists of approximately 2000 fast plastic
scintillators, each with dimensions of 404025 mm, equiped
with SiPM (Silicon Photomultiplier) with an active area of 66 mm.
The signal readout from these scintillators will employ a single-threshold
multichannel Time-to-Digital Converter (TDC) to measure their response time and
amplitude using the time-over-threshold (ToT) method. This article focuses on
the analytical description of the signals from the plastic scintillator
detectors equipped with silicon photomultipliers. This description is crucial
for establishing the ToT-amplitude relationship and implementing slewing
correction techniques to improve the time resolution of the detector. The
methodology presented in this paper demonstrates that a time resolution at the
70 ps level can be achieved for the fast plastic scintillator coupled with
silicon photomultiplier with epitaxial quenching resistors
In situ dating and investigation of remarkably depleted –27.3‰ SMOW “Slushball” Earth zircons
Paleoproterozoic amphibolites and gneisses - that are remarkably depleted in ^(18)O are found in the Belomorian Belt
in Karelia, Russia [1,2]. We mapped their extent to exceed 200x20km and affect metamorphosed mafic intrusions (est.
~2.4 Ga intrusion age) and host 2.6Ga gneisses found in this 1.9 Ga collisional belt. δ^(18)O values of –7 to –27.3‰
characterize minerals and rocks from several of these localities; some of these rocks are also remarkably depleted
with respect to δD (-212 to –235‰ amphiboles). All have typical terrestrial Δ^(17)O values of 0‰. Based on previous
paleogeographic reconstructions, we attribute the origin of these exotic O and H isotope compositions to the
hydrothermal alteration associated with subglacial rifting during the Paleoproterozoic panglobal ice ages, but discuss
additional possibilities: extremely low-δ^(18)O Paleo- proterozoic sea water, and excursion of Karelia to polar latitudes. Given
that at high-T hydrothermal exchange equilibrium Δ^(18)O(rockwater) is close to zero, but water-rock interaction is rarely
100% efficient, the lowest measured δ^(18)O value in silicates likely gives the upper δ^(18)O bound for the altering meteoric
fluid; we thus continues our quest to find the lowest δ^(18)O material such as a mineral assemblage or a tiny zircon
fragment that would provide record of δ^(18)Owater
and Polarizabilities from {} Data on the Base of S-Matrix Approach
We suggest the most model-independent and simple description of the
process near threshold in framework of S-matrix
approach. The amplitudes contain the pion polarizabilities and rather
restricted information about interaction. Application of these
formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data
gives: ,
(in units system ) at the experimental values of scattering lengths. Both
values are compartible with current algebra predictions.Comment: LaTeX, 14 pages plus 6 figures (not included, available upon request)
, ISU-IAP.Th93-03, Irkuts
Принципы и направления долгосрочного стимулирования инновационной активности в социальной сфере
The article describes the main functions of socially oriented innovation in connection with technical innovations – drivers of the third industrial revolution. Analysis of domestic and foreign innovative publications helped to formulate the basic principles of innovation in the social sphere. Directions of long-term stimulation of innovation activity in conditions of digital transformation have been developed. They are based on basic principles. It is also shown that the socio-economic development of the country should be based on qualitative population growth. Otherwise, the strategic importance of socio-economic policy is nulled and futuristic uncertainty comes. It is proposed to stimulate innovation in social sectors by increasing the innovative mentality of future generations of Belarusian people, improving the exchange of data in the system of information support of science, and by increasing the number of available sources of financing for innovations.В статье рассмотрены основные функции социально ориентированных инноваций во взаимосвязи с техническими нововведениями – драйверами третьей промышленной революции. На основе анализа отечественных и зарубежных источников, посвященных вопросам инноватики, сформулированы базовые принципы инновационной активности в социальной сфере. Исходя из них, предложены направления долгосрочного стимулирования инновационной активности в условиях цифровой трансформации. Показано, что постановка любых задач социально-экономического развития должна осуществляться на основе качественного роста населения. В противном случае обнуляется стратегическая значимость социально-экономической политики и наступает футуристическая неопределенность. Стимулировать инновационную активность в социальной сфере предлагается за счет повышения новаторской ментальности будущих поколений белорусов, совершенствования обмена данными в системе информационного обеспечения НИОКР и внедрения новшеств, а также путем увеличения числа доступных источников финансирования нововведений
Measurement of Time Resolution of Scintillation Detectors with EQR-15 Silicon Photodetectors for the Time-of-Flight Neutron Detector of the BM@N Experiment
To study the dependence of the equation of state of high density nuclear
matter on the term characterizing the isospin (proton-neutron) asymmetry of
nuclear matter, it is necessary to measure azimuthal flow of neutrons as well
as azimuthal flow of charged particles from a dense nuclear matter in the
nuclear-nuclear collisions. For this purpose INR RAS is developing a new
high-granular neutron detector which will be used in the BM@N experiment at the
extracted beam of the Nuclotron accelerator at JINR (Dubna). This detector will
identify neutrons and measure their energies in the heavy-ion collisions up to
4 GeV per nucleon.
This article presents the results of measurements of the time resolution and
light yields of samples of scintillation detectors with sizes
404025 mm that will be used in a neutron detector based on
the currently available fast plastic scintillator manufactured by JINR using an
EQR15 11-6060D-S photodetector for light readout. For comparison, the results
of measurements for a detector of the same size with a fast scintillator EJ-230
and with the same type of photodetector are given. The measurements were made
on cosmic muons as well as on the electron synchrotron "Pakhra" of the Lebedev
Physical Institute of the Russian Academy of Sciences located in Troitsk,
Moscow
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