A high-power periodic nanosecond pulse source of coherent 8-cm electromagnetic radiation

The generation of short electromagnetic pulses excited in an extended slow-wave system (SWS) of a relativistic backward wave tube (BWT) operating in the so-called superradiance regime with a carrier frequency of 3.7 GHz has been simulated and experimentally studied. At a decreased magnetic field (about 0.2 T) in the SWS, the BWT generated 2.5-ns microwave pulses with a power of up to 800 MW. At a pulse repetition rate of 100 Hz, the working life of the system was limited by the lifetime of an explosive emission cathode (10⁶ pulses). The possibility of phase synchronization of the high-frequency field of the relativistic microwave oscillator with respect to the voltage pulse front is demonstrated for the first time.     

High-sensitivity accelerometer based on cold emission principle

A possibility for fabrication of a high-sensitivity accelerometer is considered. The linear acceleration of a sensor causes displacement of the proof mass electrode. The displacement detector is based on a strong dependence of the tunneling or cold emission current on the gap between the electrodes. The geometry of the electrodes that provides the best sensitivity is determined. The accelerometer with tunneling-emission electrodes is fabricated. At frequencies up to 5 kHz the resolution reaches 10/sup -4/ g/Hz/sup 1/2/ in the tunneling mode and 10/sup -3/ g/Hz/sup 1/2/ in the emission mode.     

The СПРУТ-VI Instrument Complex for the Mir Orbital Station

The basic elements of the instrument package program for orbital stations are presented. The characteristics of the -VI equipment developed for the Mir orbital station within the framework of this program are described. This equipment allows the simultaneous recording of the characteristics of near-earth space (electron, proton, and nucleus fluxes, magnetic fields, and low-frequency electromagnetic waves) and their effect on the elements of spaceborne equipment and systems. The mass of the equipment is 16 kg; the power consumption is no more than 20 W.     

Numerical electrodynamic analysis of the far-field patterns of the external Sestroretskii cube

Far-field patterns of the external Sestroretskii cube with the edge size of 1 mm for the frequencies of 1, 150, and 300 GHz are presented. The paradox of the external Sestroretskii cube and its relation to the paradox of the external Huygens cube are revealed.     

Time-domain simulation of H-plane optical distribution systems for the development of wideband multibeam active phased antenna arrays

An H-plane optical distribution system for formation of a five-beam radiation pattern of active phased antenna arrays is proposed and analyzed. The distribution system is analyzed in time domain, which allowed obtaining the results on transient processes in this system.     

A multichannel spectrometer for detecting γ rays in a wide range of time intervals during pulse neutron irradiation

A versatile spectrometer has been developed for measuring the nuclear radiation spectrum in discrete time intervals. The design and operating principle of the spectrometer are described. Since the main logical part is based on a field programmable gate array, time intervals may be tuned in a wide range without changing the spectrometer hardware. The test experiments have demonstrated the spectrometer applicability for measuring the amplitude and timing parameters of the γ response when an analyzed sample is irradiated with a pulsed neutron flux. This device can be used to solve many problems of nondestructive testing, e.g., spectrometric neutron logging, detection of explosives, identification and characterization of fissile materials.     

Synthesis and crystal structure of the disordered modification of Tl6Si2O7

A new compound ??-Tl₆Si₂O₇ has been investigated using the methods of IR spectroscopy and microprobe and X-ray diffraction analysis. The elementary unit parameters were as follows: P6₃/m, a = 9.673(2) Å, c = 3.9169(9) Å, and V = 317.4(1) ų. The structure was resolved by direct methods and corrected until R ₁ = 0.029 (wR ₂ = 0.047) for 240 reflections [F _o] ?? 4?? _F . The crystal structure of ??-Tl₆Si₂O₇ contains one symmetrically independent position of the Tl⁺ cation that forms three short (??Tl-O?? = 2.54 Å) bonds and one weak bond (2.93 Å) with the oxygen atom. One can observe a strong disordering of silicon atoms (Si-Si = 0.64 Å). The distorted tetragonal pyramids TlO₄ are linked through silicate tetrahedra into a three-dimensional framework. The interesting feature of the crystal structure of ??-Tl₆Si₂O₇ is in the presence of wide channels occupied by lone electron pairs on Tl⁺ cations. One can also mention that in most of the structures of Tl⁺ oxygen-containing salts the lone pairs are associated into separate parts in the form of micelles in channels of frameworks or other structural cavities.     

Determination of the three-dimensional velocity vector using the laser doppler measurements of unevenly sampled components

This paper describes the method for determining the three-dimensional velocity vector of the flow using the laser Doppler measurements of unevenly sampled components. This method is based on the filtering and linear interpolation of the measured velocity components in the circuit channels. It is shown in the numerical simulation and physical experiment that the method error does not exceed 2% and the results of interpolation with respect to the closest points are several times greater.     

Investigation of characteristics of planar leaky-wave antenna arrays designed for broadside radiation

The results of computer simulation and experimental investigations of new planar leaky-wave antenna arrays designed for microwave and EHF bands and for the mode of radiation normal to the aperture plane have been presented. These arrays comprise single-layer shielded dielectric waveguides and metal-strip periodic diffraction gratings. The specified antennas ensure the radiation efficiency of no less than 50% and the gain of about 28–30 dB within the 3–4% frequency band.