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The optical layout and performance characteristics of a device for measuring the four Stokes parameters are reported, and the principle of its operation is described. The device is designed for use in the NES echelle spectrograph mounted in the Nasmyth-2 focus of the 6-meter telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Tests of the device operating on the telescope showed the gain in throughput to be a factor of 2.7 and 6 in the red (5000–7000 Å Å) and blue (3500–4700 Å Å) parts of the spectrum, respectively, compared to an analyzer based on Fresnel rhombi. 相似文献
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The Main Stellar Spectrograph (MSS) of the 6-m telescope of the Special Astrophysical Observatory was developed in the early 1970s and has been in permanent operation since 1975. This instrument has been successfully kept operational for a long time by equipping it with modern detectors and significantly upgrading its optical layout. In this paper we present the main parameters of the optomechanical layout of the MSS, the design features of auxiliary devices, operational experience and statistics of the use of the instrument with various detectors, and the characteristics of the corresponding observational techniques. 相似文献
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This work is devoted to the problem of localizing the 14C cosmogenic radionuclide in a firn layer covering glaciers. The data on 14C in ice samples from the GISP2 ice core drilled on a Greenland ice dome (Summit) are analyzed. It has been indicated that
experimental values of the 14C concentration are systematically smaller than theoretically calculated values, which indicates that firn grains partially
lose 14C. Diffusion of cosmogenic 14C in firn grains and hydration of 14CO2 in a disordered ice layer, which is formed on a firn grain surface and at the boundary between ice monocrystals, are considered.
It has been indicated that these processes are among the main ones responsible for the level of radiocarbon concentration
in firn and ice samples. 相似文献
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The propagation of cosmic rays in the Earth??s atmosphere is simulated. Calculations of the omnidirectional differential flux of neutrons for different solar activity levels are illustrated. The solar activity effect on the production rate of cosmogenic radiocarbon by the nuclear-interacting and muon components of secondary cosmic radiation in polar ice is studied. It has been obtained that the 14C production rates in ice by the cosmic ray nuclear-interacting component are lower or higher than the average value by 30% during periods of solar activity maxima or minima, respectively. Calculations of the altitudinal dependence of the radiocarbon production rate in ice by the cosmic radiation components are illustrated. 相似文献
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Simple dynamic models of long-term variations in river runoff are suggested. The models are based on a small number of parameters. Stochastic differential equations associated with these models are investigated. The theoretical density of probability distribution of river runoff values--stationary solutions of the Fokker–Planck–Kolmogorov equation--coincide with the distribution densities widely used in stochastic hydrology. 相似文献
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A new thermophysical mechanism of the Caspian Sea level variations is proposed. The mechanism incorporates the effect exerted on the dynamics of the water budget of the Caspian Sea by the nonlinear dependence of the evaporation rate on the moistening of the basin. 相似文献
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This study is devoted to the production of 14C by the secondary cosmic radiation in polar ice. The radiocarbon production in the reactions caused by the nuclear-active
and muon components is considered. The data on 14C from the Vostok and Taylor Dome Antarctic boreholes are analyzed. The 14C concentration values at depths larger than the firn—ice boundary by a factor of 2—3 can be explained by a deep production
of radiocarbon in the reactions caused by the cosmic radiation muon component. 相似文献
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Nonlinear mechanisms of long-term variations in the Caspian Sea level are described. It is shown that with account taken of the dependence of the evaporation depth from the Volga basin surface on soil moisture content and the dependence of the evaporation depth from the sea surface on its level, we obtain a fundamentally new (chaotic) oscillation mechanism with several attraction levels. The stochastic differential equations describing the water budget of the sea basin and the sea proper and the respective solutions of the Fokker–Planck–Kolmogorov equation are shown to have stationary bimodal density of the level probability. The random process, characterizing the sea level variations at a nonlinear dependence between the evaporation rate and the level is found to be non-Gaussian. Noise-induced transitions, caused by nonlinear evaporation processes are described. A new nonlinear stochastic theory describing the Caspian Sea level variations and based on predicted physical effects is suggested. 相似文献
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