Sergei N. Volkov

Decimeter-band frequency-tunable sources of high-power microwave pulses

This article describes S-band sources of high-power microwave (HPM) pulses: a resonant backward wave oscillator (BWO) producing ∼5-GW, 100-J pulses, based on the SINUS-7 electron accelerator, and a double-section vircator with a peak power of ∼1 GW and a pulse width of 20-50 ns, powered from either the SINUS-7 accelerator or the MARINA inductive-store pulse driver with a fuse opening switch.

Primary energy storages based on linear transformer stages

Primary storages based on a linear transformer scheme were developed long ago. In this scheme, the secondary turn only has to be insulated from the high output voltage. Seven years ago at the High Current Electronics Institute (HCEI) a primary storage based on a linear transformer scheme and called the Linear Transformer Driver (LTD) stage was designed. In LTD stages, the primary turn, the storage capacitors with the switches, the core, and the outer conductor of the secondary turn are integrated into the stage cavity representing one separate building block of the primary storage. The body of the LTD cavity keeps ground potential during the shot allowing us to assemble them in series or in parallel depending on load requirements. Such flexibility of the storage structure and high output power of the LTD stages allows us to replace for some applications the traditional water line technology with LTD-based primary storages that are connected directly to the load (Direct Drive Scheme-DDS). In this article, we present the design of several LTD stages developed at HCEI and give examples of high-power energy storages produced by using the LTD technology.

S-band vircator with electron beam premodulation based on compact pulse driver with inductive energy storage

This paper describes an S-band vircator system with electron beam premodulation, built on the base of the MARINA compact high-voltage pulser with inductive energy storage. The peak microwave output was /spl sim/1 GW with /spl sim/5% power efficiency and 50-ns full-width at half-maximum. The microwave frequency was constant during the pulse as determined by the resonator. Substantial spontaneous shortening of the microwave pulse was observed. Possible mechanisms for this phenomenon are discussed and supported by three-dimensional KARAT simulations.

Investigation of East Asian clouds with polarization light detection and ranging

In this paper we present results of investigation of the main optical properties of East Asian clouds with a ground-based polarization lidar placed in Daejeon, Republic of Korea. Asian dust is located in elevated layers of the atmosphere in spring, travels long distances, and causes significant damage to ecology. We present backscattering matrices of clouds obtained from polarimetric remote measurements which comprise information on the scattering and absorption properties of cloud particles, their morphology, and spatial orientation. Theory of our applied lidar polarization experiment is presented in terms of the instrumental vectors of a transmitter and a receiver. Methods of solving linear and nonlinear systems of equations comprising echo signals are considered. Some numerical and measurement results are presented to illustrate the efficiency and versatility of the method of estimating the cloud parameters.

Optimal method of linear regression in laser remote sensing

Remote lidar sensing in the photon-counting mode is now the commonly accepted method for studying atmospheric processes in the lower and free atmosphere. However, when processing signals obtained from lidar measurements, investigators necessarily face the problem of achieving accuracy in reconstructing the atmospheric parameters despite the presence of inhomogeneous noise in the measured signals. We propose an optimal method of linear regression (OMLR) of signals. The accuracy of the the method for the reconstructed signal is estimated. An example of application of the OMLR to the reconstruction of the temperature profile from the data obtained with a Raman lidar at the Siberian Lidar Station of the Institute of Atmospheric Optics (Tomsk, Russia) is given. The proposed method is distinguished by simplicity of interpretation of the criteria used, based on careful adherence to statistical principles. This method is shown to be an efficient auxiliary tool for the processing of measured data.

A Vacuum Feedthrough Insulator at a Voltage of ∼1 MV

The design and results of tests of a vacuum feedthrough insulator for a pulsed electron accelerator with a voltage of ∼1 MV, a current of ∼20 kA, and a half-height voltage-pulse duration of ≥ 400 ns are presented. A method for distributing the voltage over the sections of the insulator due to an electron emission from specially created surfaces is proposed.

Raman and fluorescent scattering matrix of spherical microparticles

In this paper, we have investigated the main properties of the Raman and fluorescent matrix of scattering by microspheres using the matrix scattering formalism. The coherent and incoherent inelastic scattering of incident light by a microsphere is described by the Stokes parameters. We demonstrate the main symmetry properties of the coherent and incoherent Raman and fluorescent scattering matrices. Numerical results are presented to illustrate the Raman scattering efficiency, cross-phase coefficient, and some other parameters of scattering by microspheres.

Morphological Tagging of Russian Texts of the XIXth Century

Tagging Russian texts of the XIXth century has been evaluated. The causes have been determined why some words turned out to be unknown to the tagger, i.e. remained without lemmas and grammatical features. The investigation showed that the main reasons of the existence of the unknown words were as follows: 1) incompleteness of the tagger dictionary, particularly in the XIXth century lexical stock; 2) failure to tag the word-formative derivates; 3) problems with some inflexion models of Old Russian; 4) insufficiency of graphemic analysis; 5) inability of taggers to process multiwords. The results obtained provide a baseline to improve premorphological processing of Russian texts and to work out the more sophisticated approaches to morphological analysis.

Measurement of Aerosols and Ice Clouds Using Ellipsometry Lidar

We have developed ellipsometry lidar and measured aerosol and ice-cloud characteristics. To measure a full normalized backscattering phase matrix (NBSPM) composed of nine elements, we have designed an optical system with three kinds of transmission and three kinds of reception, composed of λ/2 waveplate, λ/4 waveplate and empty optic. To find systematic optical errors, we used clean day middle-altitude (4-6km) lidar signals for which the aerosol’s concentration was small and its orientation chaotic. After calibrating our lidar system, we have calculated NBSPM elements scattered from an aerosol and from an ice cloud. In the case of an aerosol, we found that the off-diagonal values m 12 ,...,m 34 of the NBSPM are smaller than those for a cirrus cloud. Also, the off-diagonal values of the NBSPM from a cirrus cloud depend on atmospheric conditions.