93 research outputs found
Gas Purity effect on GEM Performance in He and Ne at Low Temperatures
The performance of Gas Electron Multipliers (GEMs) in gaseous He, Ne, He+H2
and Ne+H2 was studied at temperatures in the range of 3-293 K. This paper
reports on previously published measurements and additional studies on the
effects of the purity of the gases in which the GEM performance is evaluated.
In He, at temperatures between 77 and 293 K, triple-GEM structures operate at
rather high gains, exceeding 1000. There is an indication that this high gain
is achieved through the Penning effect as a result of impurities in the gas. At
lower temperatures the gain-voltage characteristics are significantly modified
probably due to the freeze-out of these impurities. Double-GEM and single-GEM
structures can operate down to 3 K at gains reaching only several tens at a gas
density of about 0.5 g/l; at higher densities the maximum gain drops further.
In Ne, the maximum gain also drops at cryogenic temperatures. The gain drop in
Ne at low temperatures can be re-established in Penning mixtures of Ne+H2: very
high gains, exceeding 104, have been obtained in these mixtures at 30-77 K, at
a density of 9.2 g/l which corresponds to saturated Ne vapor density at 27 K.
The addition of small amounts of H2 in He also re-establishes large GEM gains
above 30 K but no gain was observed in He+H2 at 4 K and a density of 1.7 g/l
(corresponding to roughly one-tenth of the saturated vapor density). These
studies are, in part, being pursued in the development of two-phase He and Ne
detectors for solar neutrino detection.Comment: 4 pages, 7 figure
Introduction of All-Russian physical and sport complex «GTO» in the Republic of Khakassia
The experience of the introduction of the All-Russia physical culture and sports complex «GTO» in the Republic of Khakassia is presented. Activities carried out for the entire period, analyzed the results. The interaction of the structures responsible for the implementation of the complex is reflectedПредставлен опыт внедрения всероссийского физкультурно-спортивного комплекса «ГТО» в Республике Хакасия. Мероприятия, проведенные за весь период, проанализированы полученные результаты. Отражено взаимодействие структур, ответственных за внедрение комплекс
Experimental Investigation of the Nature of the Knee in the Primary Cosmic Ray Energy Spectrum with the GAMMA experiment
We present preliminary results obtained by a novel difference method for the
study of the nature of the knee in the energy spectrum of the primary cosmic
radiation. We have applied this method to data from the GAMMA experiment in
Armenia. The analysis provides evidence for the possible existence of a nearby
source of primary cosmic rays in the Southern hemisphere.Comment: 17 pages, 5 figure
Eta-mesic nuclei in relativistic mean-field theory
With the eta-nucleon (eta N) interaction Lagrangian deduced from chiral
perturbation theory, we study the possible eta-mesic nuclei in the framework of
relativistic mean-field theory. The eta single-particle energies are sensitive
to the eta N scattering length, and increase monotonically with the nucleon
number A. If the scattering length is in the range of a^{eta N}=0.75-1.05 fm
and the imaginary potential V_{0}-15 MeV, some discrete states of C, O and Ne
eta bound states should be identified in experiments. However, when the
scattering length a^{eta N} 30 MeV,
no discrete eta meson bound states could be observed in experiments.Comment: 6 page
Oxidation of cellulose in pressurized carbon dioxide
This work presents first results upon oxidation of type II cellulose by nitrogen dioxide dissolved in carbon dioxide at high pressure. This reaction leads to oxidized cellulose, a natural-based bioresorbable fabric used for biomedical applications. The oxidation reaction takes place in a heterogeneous fluid–solid system. Kinetics of oxidation is presented here and effects of operating conditions such as pressure, temperature and initial moisture content of cellulose are investigated. Results are presented in terms of degree of oxidation of cellulose and quality of the final oxidized cellulose, which has been characterized using liquid-state and solid-state 13C NMR. The experimental results show the existence of possible secondary reactions which may lead to oxidized cellulose with insufficient mechanical strength. An attempt is made to evidence and understand the role of CO2 as a solvent in this system. Indeed, although supercritical CO2 appears to be a suitable candidate as a solvent for oxidation reactions, some inhibiting effect on nitrogen dioxide activity are observed in this case
Expert system application for reactive power compensation in isolated electric power systems
Effective electricity use can be an option which enables to achieve significant economy while generating and transmitting of electricity. One of the most important things is to improve the electricity quality through reactive power correction up to optimum values. The current article presents the solution to compensate the reactive power in the distribution networks, in GornoBadakhshan Autonomous Oblast (GBAO) with the use of the advanced technologies based on the data collection within real time. The article describes the methodology of fuzzy logic application and bio-heuristic algorithms for the suggested solution effectiveness to be determined. Fuzzy logic application to specify the node priority for compensating devices based on the linguistic matrix power loss and voltage gives the possibility to the expert to take appropriate solutions for compensating devices installation location to be determined. The appropriate (correct) determination of the compensating devices installation location in the electric power system ensures the effective regulation of the reactive power with the least economic costs. Optimization problems related to the active power loss minimization are solved as well as the cost minimization with compensating devices to ensure the values tan(φ) not exceeding 0.35 through reducing multi-objective problem to the single-objective one using linear convolution
GEM operation in helium and neon at low temperatures
We study the performance of Gas Electron Multipliers (GEMs) in gaseous He, Ne
and Ne+H2 at temperatures in the range of 2.6-293 K. In He, at temperatures
between 62 and 293 K, the triple-GEM structures often operate at rather high
gains, exceeding 1000. There is an indication that this high gain is achieved
by Penning effect in the gas impurities released by outgassing. At lower
temperatures the gain-voltage characteristics are significantly modified
probably due to the freeze-out of impurities. In particular, the double-GEM and
single-GEM structures can operate down to 2.6 K at gains reaching only several
tens at a gas density of about 0.5 g/l; at higher densities the maximum gain
drops further. In Ne, the maximum gain also drops at cryogenic temperatures.
The gain drop in Ne at low temperatures can be reestablished in Penning
mixtures of Ne+H2: very high gains, exceeding 10000, have been obtained in
these mixtures at 50-60 K, at a density of 9.2 g/l corresponding to that of
saturated Ne vapor near 27 K. The results obtained are relevant in the fields
of two-phase He and Ne detectors for solar neutrino detection and electron
avalanching at low temperatures.Comment: 13 pages, 14 figures. Accepted for publishing in Nucl. Instr. and
Meth.
Small eta-N scattering lengths favour eta-d and eta-alpha states
Unstable states of the eta meson and the 3He nucleus predicted using the time
delay method were found to be in agreement with a recent claim of eta-mesic 3He
states made by the TAPS collaboration. Here, we extend this method to a
speculative study of the unstable states occurring in the eta-d and eta-4He
elastic scattering. The T-matrix for eta-4He scattering is evaluated within the
Finite Rank Approximation (FRA) of few body equations. For the evaluation of
time delay in the eta-d case, we use a parameterization of an existing Faddeev
calculation and compare the results with those obtained from FRA. With an eta-N
scattering length, fm, we find an eta-d unstable
bound state around -16 MeV, within the Faddeev calculation. A similar state
within the FRA is found for a low value of , namely, fm. The existence of an eta-4He unstable bound state close to
threshold is hinted by fm, but is ruled out by
large scattering lengths.Comment: 21 pages, LaTex, 7 Figure
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