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V. A. Baskov 《JETP Letters》2014,99(12):675-678
A method for the detection of 26- and 28-GeV electrons by a directional spectrometer based on oriented tungsten, tungstate, and garnet crystals has been reported. In spite of an anomalous character of the development of an electromagnetic shower at the initial stage in a crystal oriented along the 〈111〉 axis, the relative energy release of the shower in the spectrometer behind the crystal at the final stage is described by the standard dependence of the development of the electromagnetic shower. 相似文献
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N. A. Van Bui I. M. Martin A. Turtelli jr. M. I. Fradkin V. V. Sibikin Yu. I. Stozhkov A. Svirzhevskaya 《Il Nuovo Cimento C》1989,12(5):673-678
Summary To investigate the variation of the flux of cosmic radiation in the vicinity of the Earth, stratospheric balloon soundings
are performed weekly at Campinas (Brazil). During some soundings, enhancements of the counting rates are detected. In this
paper data from these excesses as well as their analysis are shown. It seems to indicate that possibly high-energy electrons
are injected from the lower boundary of the radiation belt into the stratosphere.
Riassunto Per ricercare la variazione del flusso delle radiazioni cosmiche in prossimità della Terra, sono fatti funzionare settimanalmente palloni sonda a Campinas (Brasile). In alcune sonde si registrano aumenti delle frequenze di conteggio. In questo lavoro si mostrano dati da questi eccessi nonché le loro analisi. Ciò sembra indicare che gli elettroni ad alta energia sono probabilmente immessi dallo strato inferiore della fascia di radiazioni nella stratosfera.
Резюме для исследования изменения потока космического излучения в окрестности Земли еженедельно запускаются стратосферные шары-зонды в лаборатории Кампинас (Бразилия). Во время некоторых зондирований зарегистрированы увеличения интенсивности излучения. В этой статье приводятся данные измерений и их анализ. Проведенный анализ показывает, что эти случаи возможно связаны с электронами высоких энергий, инжектированными из нижней границы радиационного пояса в стратосферу.相似文献
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The characters are given for the irreducible nonequivalent weighted corepresentations for all possible types of coequivalent weights for groups D2h, D4h, and D6h. 相似文献
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M.A. Kornberg J.E. Miraglia 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):45-51
We present numerical results for the photoelectron spectrum in double ionization by keV photons in the quasiequal-energy sharing
region. In this region of the spectrum, the relevant ionizing mechanism is due to a mutual sharing of the photon momentum
by both electrons, with small momentum transferred to the atomic nucleus. Calculations were performed for photon energies
of 25 and 50 keV, where retardation effects are fundamental, while final-state correlations are of minor importance. The spectra
present a two-peak structure, with maxima located at the photoelectron energies , with the photon energy in atomic units. We discuss the general features of the spectrum in terms of the picture of the photoionization
of two free electrons, and we propose a way of detecting the contribution by experiments.
Received 24 January 2000 相似文献
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The range of electron in KCl 〈100〉 and KCl 〈110〉 crystals in the energy between 30 and 60 keV have been experimentally determined. The data fit an equation of the type, R = kEn. The values of k and n exhibit crystalline orientation dependence. 相似文献
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The principal theorems concerning these characters are presented. 相似文献
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The differential and total cross sections are calculated for the ionization of helium-like ions that is accompanied by the excitation of residual ions to ns states owing to an electron impact. Nonrelativistic perturbation theory in electron–electron interaction with Coulomb functions used for a zero-order approximation underlies these calculations. The expressions obtained in this way have a universal character. They are applicable at moderate values of the target charge number Z and high energies of incident electrons. A comparison with total cross sections calculated for the helium atom within various theoretical approaches is performed. 相似文献
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We have studied the propagation of a surface acoustic waves (SAW), in a structure constituted by a 2D phononic film (a few micrometers thick and having lattice constants of a few hundreds of micrometers in the two directions of the propagation plane) deposited onto a homogeneous semi-infinite substrate. First, we have calculated the dispersion relations of the acoustic modes by using a plane waves expansion method. We found that the surface branch exhibits both the folding effect and a band gap for the propagation along some particular directions. This is a very interesting result which demonstrates that the effects related to the existence of the band gap (sound velocity dispersion, diffraction, refraction, ultrasound tunneling, etc.) can all appear, even if the thickness of the phononic film is much less than the penetration depth of the SAW. Then, we used an all-optical technique to monitor the spectral content of the SAW propagating along the GammaX direction in the reduced Brillouin zone. We show that a wave with frequency in the stop band, is destructively diffracted after it propagates through less than ten periods. Finally, we report on measurements of the Rayleigh wave phase velocity and we show that the transit time is independent of the distance traveled inside the phononic crystal, suggesting that tunneling trough the sample is involved. 相似文献
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A method is presented for the numerical calculation of the differential, total, and transport cross sections of elastic scattering, and results are given for the scattering of fast electrons with energies in the range 10 keV to 1 MeV on neutral atoms of uranium, silver, argon, aluminum, and oxygen. Approximations are obtained for the energy dependences of the scattering cross sections.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 8–12, January, 1980. 相似文献
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V. V. Syshchenko A. I. Tarnovskii N. F. Shul’ga 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(2):365-368
Incoherent bremsstrahlung of high-energy particles in a crystal is caused by the thermal scattering of atoms with regard to
their equilibrium positions in the lattice. A previously developed procedure for the simulation of incoherent emission is
applied to the case of electron motion in a sinusoidally bent crystal. The results of the simulation agree with the data of
recent experiments at the Mainz Microtron (MAMI). The possibility for utilizing sinusoidally bent crystals as undulators is
discussed. 相似文献
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The properties of the coherent X-ray radiation of the ultrarelativistic electrons in a crystal are considered. The total number of X-ray and resonant γ-ray quantum emitted in a crystal under diffraction conditions are calculated. 相似文献
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V. G. Neudatchin I. T. Obukhovsky L. L. Sviridova D. K. Fedorov N. P. Yudin 《Physics of Atomic Nuclei》2007,70(5):855-861
The electroproduction of charged rho mesons on a nucleon under conditions of quasielastic kinematics [Q 2 > 2 (GeV/c)2, W > 3 GeV, and ω ρ ? q 0 in the laboratory frame] is considered. The main diagrams involved in this process are taken into account, and it is shown that the case of rho-meson knockout by a longitudinal photon is dominated by the t-channel pole diagram featuring a rho meson, so that direct rho-meson electroknockout makes a leading contribution to the process being considered. Questions concerning the gauge invariance of the electroproduction process are considered in detail, along with contact terms that inevitably arise in employing form factors in ρNN vertices and which are necessary for restoring gauge invariance. It is shown that the structure of these contact terms is not determined exclusively by the requirement that the electroproduction amplitude be gauge-invariant and may be such that the corresponding correction to the dominant diagram due to these terms proves to be suppressed in the quasielastic region (with increasing Q 2), with the result that the t-pole process featuring a rho meson remains dominant; at the same time, the contribution of this correction is significant at low Q 2 or in the case of photoproduction, modifying substantially the electroproduction cross section. 相似文献
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L. Jakubowski J. Zebrowski V.V. Plyusnin K. Malinowski M.J. Sadowski M. Rabinski H. Fernandes C. Silva P. Duarte 《Radiation measurements》2010,45(9):1014-1019
The paper concerns detectors of the Cherenkov radiation which can be used to measure high-energy electrons escaping from short-living plasma. Such detectors have high temporal (about 1 ns) and spatial (about 1 mm) resolution. The paper describes a Cherenkov-type detector which was designed, manufactured and installed in the ISTTOK tokamak in order to measure fast runaway electrons. The radiator of that detector was made of an aluminium nitride (AlN) tablet with a light-tight filter on its front surface. Cherenkov signals from the radiator were transmitted through an optical cable to a fast photomultiplier. It made possible to perform direct measurements of the runaway electrons of energy above 80 keV. The measured energy values and spatial characteristics of the recorded electrons appeared to be consistent with results of numerical modelling of the runaway electron generation process in the ISTTOK tokamak. 相似文献
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Yu.N. Adishchev A.N. Didenko V.V. Kaplin A.P. Potylitsin S.A. Vorobiev 《Physics letters. A》1981,83(7):337-340
γ-ray spectra have been measured for (110) and (111) planar channeling of 600–900 MeV electrons in a diamond crystal. It is shown that in the case of (111) crystallographic planes the influence of molecular-type motion on the formation of the spectra is predominant. 相似文献
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It is shown that the production of transversally polarized electrons and positrons by unpolarized γ-quanta with energies of tens and hundreds of GeV, is possible in thin crystal plates. 相似文献
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The surface resonance RHEED problem is solved exactly using the tight-binding model for the case of the off-Bragg orientation of the incident beam. Explicit expressions are obtained for the wave function and for the resonance part of the surface reflectivity. It is shown that the dominant contribution to the reflectivity results from a process involving at least several states each localized in the potential of adjacent atomic planes parallel to the surface, and in the crystal bulk the wave function of the scattering problem belongs to the continuum of Bloch states. The analytical solution found provides an accurate approximation to the results of numerical integration of the relevant equations of the theory of RHEED, and demonstrates that no concept of a surface state is required for interpretation of the angular dependence of the reflectivity of a clean crystal surface in the vicinity of the resonance condition. 相似文献