Low-frequency intensity fluctuations of radiation from a distant source in the infrared region of the spectrum. II

The results are considered of signal-fluctuation measurements of a thermal source in the infrared region of the spectrum on an extended surface path. Experimental averaging functions are obtained for receiver-transmitting apertures in the case of large limits of variation of the latter. The dependence of the dispersion of the fluctuations on the wavelength of the radiation is investigated over the range 1.06 to 3.9 .Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 111–115, February, 1975.     

Estimating the spectrum of a component of a digital signal containing an intense interference

A spectral analysis technique based on approximating a set of counts by a first-degree trigonometric polynomial with a varying frequency of its harmonics. With this technique, the parameters of a signal component that is two orders of magnitude weaker than an interference are estimated at a frequency ratio of 0.82.     

Influence of the periodic motion of a monochromatic light source on the spectrum of its radiation

The influence of the periodic motion of a monochromatic light source on the observed spectrum of its radiation in the far-field and near-field zones is considered. The appearance of components shifted in frequency (harmonics of the oscillation frequency of the source) is demonstrated. The spatial structure of harmonics is investigated, and the presence of optical vortices in these harmonics is shown.     

Evolution of the angular power spectrum of scattered radiation from a point source upon propagation in a turbid medium

The propagation of radiation from a point source through a plane layer of an absorbing medium with smooth random permittivity inhomogeneities is considered for the case in which the source and a receiver are spaced by different distances from the layer boundaries. The angular power spectra of the scattered radiation are calculated by the method of statistical modeling for different values of the layer thickness, positions of the source and the receiver relative to the layer, and absorption in the layer. The results for the moments of the angular power distribution obtained earlier in the small-angle approximation are fully confirmed. The transformation of the angular power spectrum upon variation of the source or receiver position with respect to the layer is analyzed for the first time.     

The influence of the planar potential form on the channeling radiation spectrum

Energies for transitions between bound states for planar-channeled electrons are calculated. The continuum planar potential constructed from atomic ones in Molier and Hartree-Fock-Slater approximation are used. It is shown that the H-F-S line energies calculations are in a good agreement with the experimental data for diamond.     

光源对激光超声信号特性的影响分析

通过已搭建好的激光超声检测实验平台,在保持相同激光脉冲能量和相同探测位置的条件下,重点研究了点光源与线光源产生的超声信号的特点和区别。研究了不同探测位置点光源与线光源激发出的超声信号幅值以及产生的超声信号波形。实验发现:在同一探测位置下,将点光源换成线光源后,产生的超声信号幅值由1.3 V提高到1.7 V,提高了0.4 V;在探测位置逐渐增大的情况下,点光源激发出超声信号幅值的衰减幅度为75.78%,而线光源激发出的超声信号幅值的衰减幅度为34.92%。结果表明,在功率密度相同的情况下,线光源产生的超声信号要比点光源产生的超声信号幅值提高40.86%,产生较强的表面波,提高了信噪比。     

Reflection of radiation from the walls of a cylindrical source

An equation is derived to account for the radiation reflected from the walls of a cylindrical source, under the assumptions that the plasma filling the source is uniform throughout the volume and that there is no radiation diffusion or reabsorption. Recommendations are given for eliminating the effect of the reflected radiation and for improving the measurement accuracy through the use of a mirror behind the cylinder.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 4, pp. 14–19, April, 1969.     

The influence of the radiation spectrum bandwidth on the resolution of an image up-converter

The influence of the infra-red spectrum bandwidth on the transverse resolution of an image up-converter is investigated. It is shown that by suitable placing of the infra-red image plane, the deterioration of the resolution due to the infra-red spectrum bandwidth does not occur.     

Experimental study of the output radiation spectrum of a gyrotron with partial reflection of the output signal

We present the results of experimental studies of the effect of reflection of microwave radiation from a dielectric window on the frequency characteristics of the output signal of a technological gyrotron. It is shown that the spectrum width increases several times due to the effect of reflections. Institute of Applied Physics of the Russian Academy of Sciences, GYCOM Ltd., Nizhny Novgorod, Russia Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 4, pp. 440–444, September., 2000.     

Vacuum-sealed miniature modulated x-ray source and the influence factors of x-ray intensity

The vacuum-sealed miniature modulated x-ray source(VMMXS) with a hot cathode is fabricated via the singlestep brazing process in a vacuum furnace. An experiment following the VMMXS is implemented to present its performances, including the influence of grid electrode potential on x-ray intensities. The modulation type of the grid electrode as a switch is proposed, and its feasibility is successfully demonstrated. It is noteworthy to discover a phenomenon for the first time, to the best of our knowledge, that the high repetition frequency grid pulse of the VMMXS has a significant effect on the x-ray intensity. The probable cause for this new finding is analyzed.     

Fiber-optic-based absolute displacement sensors at 1500 nm by means of a variant of channeled spectrum signal recovery

An absolute displacement-sensing system based on channeled spectrum processing capable of simultaneous interrogation of fiber Bragg gratings and fiber-optic interferometric sensors is presented in which the role of the optical spectrometer is performed by a scanning Fabry-Perot filter. We demonstrate a resolution of +/-50 nm with an estimated dynamic range of 1 part in 10(5).     

Computer modeling of a large-area integrating sphere uniform radiation source for calibration of satellite remote sensors

To meet the pre-launch radiometric calibration requirements of large field of view (FOV) imaging remote sensors, a large-area integrating sphere uniform radiation source (ISURS) based on a 1600 mm diameter internally illuminated integrating sphere with a 620 mm diameter exit port was designed. The software TracePro based on ray-tracing method was applied to computer modeling of the ISURS. It is shown that the angle of internal radiation source from the center of the sphere is an important factor affecting the spatial radiance uniformity at exit port. Taking this factor into account, the model established is able to obtain the important characteristics of the sphere source. With the characteristics obtained, the ISURS was manufactured and its optical parameters were measured. The measurement result of the spatial radiance uniformity of the large-area ISURS was 99.19%. There is a discrepancy of 0.12% between measured and simulated results. It is demonstrated that the method used and the model established can increase the efficiency of designing large-area sphere radiation source.     

The influence of the electromagnetic radiation of low intensity on toxicity of an aqueous medium

The toxicity of solutions of phenol in combination with cadmium and cobalt for a culture of micro-seaweed and the opportunity of decreasing their toxicity by the influence of electromagnetic radiation in the range of the highest frequencies (UHF irradiation) are studied. The synergism between phenol and metals and a decrease in their toxicity under the influence of electromagnetic radiation are revealed.