343 research outputs found
Depth of maximum of extensive air showers and cosmic ray composition above 10**17 eV in the geometrical multichain model of nuclei interactions
The depth of maximum for extensive air showers measured by Fly's Eye and
Yakutsk experiments is analysed. The analysis depends on the hadronic
interaction model that determine cascade development. The novel feature found
in the cascading process for nucleus-nucleus collisions at high energies leads
to a fast increase of the inelasticity in heavy nuclei interactions without
changing the hadron-hadron interaction properties. This effects the development
of the extensive air showers initiated by heavy primaries. The detailed
calculations were performed using the recently developed geometrical multichain
model and the CORSIKA simulation code. The agreement with data on average depth
of shower maxima, the falling slope of the maxima distribution, and these
distribution widths are found for the very heavy cosmic ray mass spectrum
(slightly heavier than expected in the diffusion model at about 3*10**17 eV and
similar to the Fly's Eye composition at this energy).Comment: 11pp (9 eps figures
First Results of Fast One-dimensional Hybrid Simulation of EAS Using CONEX
A hybrid simulation code is developed that is suited for fast one-dimensional
simulations of shower profiles, including fluctuations. It combines the Monte
Carlo simulation of high energy interactions with a fast numerical solution of
cascade equations for the resulting distributions of secondary particles.
Results obtained with this new code, called CONEX, are presented and compared
to CORSIKA predictions.Comment: 4 pages, 4 figures, to appear in the proceedings of the XIII
ISVHECRI, Pylos, 200
Designing negative impedance converter based on the dual gate MOSFET
In this work, an experience of designing the negative impedance converter reported. Its purpose is antennas matching during the UHF ground penetrating radar designing. The possibility of designing the negative impedance converter based on dualgate MOSFET transistors is considered. Stability of operation of the device is analyzed. Discussion of a possibility of combination of devices of the negative impedance converter and adjustable attenuator is also given.В работе описывается опыт проектирования отрицательного конвертера импеданса (ОКИ), предназначенно- го для согласования малогабаритных антенн ОВЧ диапазона в интересах построения радиолокатора подповерхностного зондирования. Рассматривается возможность построения конвертера импеданса на основе двухзатворных полевых транзисторов. Проанализирована стабильность работы устройства. Также приведено обсуждение возможности совмещения устройств конвертера импеданса и регулируемого аттенюатора за счёт регулируемой крутизны проходной характеристики МОП-транзисторов
Evaluating the possibility of designing three-dimensional ground penetrating mobile technology
На основании апробированного подповерхностного радиолокатора СВЧ диапазона строится ОВЧ вариант комплекса при условии пропорционального сохранения точностных характеристик. Приводятся основные принципы построения системы, обеспечивающие конкурентоспособность и выгодно выделяющие комплекс перед другими известными работами. Также разработан ряд аппаратурных и программных средств для построения системы. В пакете AWR MO создана модель отрицательного конвертера импеданса (ОКИ), позволяющего реализовать активное широкополосное не перестраиваемое согласование. В программе ANSYS HFSS создана модель ферритовой антенны ОВЧ диапазона, её параметры в формате .sNp импортированы в AWR для реализации согласования. Данные модели позволяют проводить дальнейшие исследования и разрабатывать антенную систему подповерхностного радиолокатора.UHF ground penetrating radar is suggested based on the approved VHF ground penetrating radar implementation. The purpose consists in proportional saving of precision characteristics. The basic principles of creation of system also described. They are providing competitiveness and favourably selecting suggested system before other known decisions. A few hardwares and softwares are also developed for complete designing the system. Model of the Negative impedance converter (NIC) designed in the AWR MO. It allows creating an active wideband not tunable matching circuit. Model of the VHF ferrite antenna designed in the ANSYS HFSS. Its parameters imported to AWR using .sNp format. These models allows to do further investigations and designing the ground penetrating radar antenna system
Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime
Electron self-injection and acceleration until dephasing in the blowout
regime is studied for a set of initial conditions typical of recent experiments
with 100 terawatt-class lasers. Two different approaches to computationally
efficient, fully explicit, three-dimensional particle-in-cell modelling are
examined. First, the Cartesian code VORPAL using a perfect-dispersion
electromagnetic solver precisely describes the laser pulse and bubble dynamics,
taking advantage of coarser resolution in the propagation direction, with a
proportionally larger time step. Using third-order splines for macroparticles
helps suppress the sampling noise while keeping the usage of computational
resources modest. The second way to reduce the simulation load is using
reduced-geometry codes. In our case, the quasi-cylindrical code CALDER-CIRC
uses decomposition of fields and currents into a set of poloidal modes, while
the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the
interaction allows using just two modes, reducing the computational load to
roughly that of a planar Cartesian simulation while preserving the 3D nature of
the interaction. This significant economy of resources allows using fine
resolution in the direction of propagation and a small time step, making
numerical dispersion vanishingly small, together with a large number of
particles per cell, enabling good particle statistics. Quantitative agreement
of the two simulations indicates that they are free of numerical artefacts.
Both approaches thus retrieve physically correct evolution of the plasma
bubble, recovering the intrinsic connection of electron self-injection to the
nonlinear optical evolution of the driver
A model for net-baryon rapidity distribution
In nuclear collisions, a sizable fraction of the available energy is carried
away by baryons. As the baryon number is conserved, the net-baryon
retains information on the energy-momentum carried by the incoming nuclei. A
simple and consistent model for net-baryon production in high energy
proton-proton and nucleus-nucleus collisions is presented. The basic
ingredients of the model are valence string formation based on standard PDFs
with QCD evolution and string fragmentation via the Schwinger mechanism. The
results of the model are presented and compared with data at different
centre-of-mass energies and centralities, as well as with existing models.
These results show that a good description of the main features of net-baryon
data is possible in the framework of a simplistic model, with the advantage of
making the fundamental production mechanisms manifest.Comment: 9 pages, 12 figures; in fig. 11 a) the vertical scale was correcte
Cosmic Ray Air Shower Characteristics in the Framework of the Parton-Based Gribov-Regge Model NEXUS
The purpose of this paper is twofold: first we want to introduce a new type
of hadronic interaction model (NEXUS), which has a much more solid theoretical
basis as, for example, presently used models like QGSJET and VENUS, and ensures
therefore a much more reliable extrapolation towards high energies. Secondly,
we want to promote an extensive air shower (EAS) calculation scheme, based on
cascade equations rather than explicit Monte Carlo simulations, which is very
accurate in calculations of main EAS characteristics and extremely fast
concerning computing time. We employ the NEXUS model to provide the necessary
data on particle production in hadron-air collisions and present the average
EAS characteristics for energies 10^14 - 10^17 eV. The experimental data of the
casa-blanka group are analyzed in the framework of the new model.Comment: 15 pages, 8 figure
Projective Invariance and One-Loop Effective Action in Affine-Metric Gravity Interacting with Scalar Field
We investigate the influence of the projective invariance on the
renormalization properties of the theory. One-loop counterterms are calculated
in the most general case of interaction of gravity with scalar field.Comment: 10 pages, LATE
Influence of hadronic interaction models and the cosmic ray spectrum on the high energy atmospheric muon and neutrino flux
The recent observations of muon charge ratio up to about 10 TeV and of
atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed
interest into the high-energy interaction models and cosmic ray primary
composition. A reviewed calculation of lepton spectra produced in cosmic-ray
induced extensive air showers is carried out with a primary cosmic-ray spectrum
that fits the latest direct measurements below the knee. In order to achieve
this, we used a full Monte Carlo method to derive the inclusive differential
spectra (yields) of muons, muon neutrinos and electron neutrinos at the surface
for energies between 80 GeV and hundreds of PeV. The air shower simulator {\sc
corsika} 6.990 was used for showering and propagation of the secondary
particles through the atmosphere, employing the established high-energy
hadronic interaction models {\sc sibyll} 2.1, {\sc qgsjet-01} and {\sc
qgsjet-ii 03}. We show that the performance of the interaction models allows
makes it possible to predict the spectra within experimental uncertainties,
while {\sc sibyll} generally yields a higher flux at the surface than the
qgsjet models. The calculation of the flavor and charge ratios has lead to
inconsistent results, mainly influenced by the different representations of the
K/ ratio within the models. Furthermore, we could quantify systematic
uncertainties of atmospheric muon- and neutrino fluxes, associated to the
models of the primary cosmic-ray spectrum and the interaction models. For most
recent parametrizations of the cosmic-ray primary spectrum, atmospheric muons
can be determined with an uncertainty smaller than % of the
average flux. Uncertainties of the muon- and electron neutrino fluxes can be
calculated within an average error of % and %,
respectively.Comment: 16 pages, 10 figures, version 2 includes analytic approximatio
One-dimensional Hybrid Approach to Extensive Air Shower Simulation
An efficient scheme for one-dimensional extensive air shower simulation and
its implementation in the program CONEX are presented. Explicit Monte Carlo
simulation of the high-energy part of hadronic and electromagnetic cascades in
the atmosphere is combined with a numeric solution of cascade equations for
smaller energy sub-showers to obtain accurate shower predictions. The developed
scheme allows us to calculate not only observables related to the number of
particles (shower size) but also ionization energy deposit profiles which are
needed for the interpretation of data of experiments employing the fluorescence
light technique. We discuss in detail the basic algorithms developed and
illustrate the power of the method. It is shown that Monte Carlo, numerical,
and hybrid air shower calculations give consistent results which agree very
well with those obtained within the CORSIKA program
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