Том 61, № 3 (2018)

We present the results of simultaneous measurements of the total electron content (TEC) of the ionosphere on the GPS signal path and the ionospheric artificial airglow in the atomic oxygen red line (λ = 630 nm) during HF pumping of the ionosphere by the Sura facility radiation. It is very likely that when the “navigation satellite—GPS receiver” path of a signal crosses the artificial airglow spot, the maximum brightness of the latter on the line of sight of the optical device at the navigation satellite was observed in the region of the TEC minimum.

We consider the problem of extracting an acoustic signal of an individual source in the presence of a set of spatially separated sources when reception is performed using a microphone array. In this case, it is assumed that the extracted-signal source is located in the preliminarily known limited spatial region. Such a problem is of practical value, e.g., for speech listening in crowded areas, extracting signals from individual sources in the problems of acoustic diagnostics of various mechanical systems, etc. An adaptive spatial-processing algorithm, which is based on using the interference model in the form of a set of sources with arbitrary unknown direction vectors, is proposed to independently solve the above-mentioned problem for each narrow band of the received signal. The advantage of the proposed method is its robustness to the discrepancies between the used model and the actual conditions. Such a robustness is achieved without using a priori data on the character of the errors in the used model. We present the results of the speech-signal extraction using numerical simulation and the experimental data for the scenarios which involve the presence of high-power interference sources, as well as the errors when specifying the direction vector. The obtained results demonstrate a higher efficiency of using the proposed method under the actual conditions compared with other available techniques.

We present a theoretical study and a computer simulation of characteristics of the undulator radiation in single-pass free-electron lasers (FELs). Using a phenomenological model describing the dynamics of the radiated power in FELs with allowance for the basic loss, we study generation of harmonics in the X-ray range in a FEL with a two-frequency undulator. We study the possibility to achieve a hundredfold increase in the radiation intensity of the nth harmonic in a FEL, in which the electron-phase shift by kπ/n with respect to photons occurs between undulator sections, where k = 2, 4, . . . . The advantages of using a two-frequency undulator in a single-pass FEL and the possibility of generating the high-power X-ray radiation by the FEL at the harmonic wavelengths 2.3–3.3 nm in the linear regime are demonstrated. The FEL is compared with the two-frequency undulator and the conventional plane undulator. Additionally, generation of radiation having a power of tens of megawatts is studied at the wavelength λ ≈ 3.27 nm in a multistage FEL with a length of 40 m, an off-the-shelf excimer ultraviolet seed laser, which operates at a wavelength of 157 nm, and an electron beam having an energy of about 0.6 GeV.