The work is devoted to the registration and the study of the properties of cylindrical shock waves generated in the fast discharge (
dI
/
dt
∼ 10
12
A/s) inside the ceramic tube (Al
2
O
3
) filled by ...argon at pressures of 100 and 300 Pa. The shock wave appears at the inner wall of the insulator and moves to the discharge axis with a velocity of about (3−4) × 10
6
cm/s with subsequent cumulation. The plasma behind the front is heated enough to produce radiation in the vacuum ultraviolet (VUV) region, which makes it possible to study its structure by means of a pinhole camera with a microchannel plate detector. The time resolution of the registration system was 10 ns. The analysis of VUV spectra of the plasma shows that the electron temperature behind the shock wave front is about several eV; after the moment of cumulation, its temperature increases to 20–30 eV.
The article presents the results of numerical calculations of the natural spectral profile of the transitions originating from the autoionization states. It is shown that this profile is different ...for two cases of the population of the initial state—inner-shell collisional excitation and dielectronic recombination. It is close to Lorenz shape in the first case, and it is Fano profile in the second case.
The article describes the algorithm for seismic imaging data processing that enables detecting and evaluating geological anomalies based on the system of specific criteria. Employing the algorithm we ...can complete the process of profile record, amplitude and velocity spectra computation, filtering and imaging of T-X curves. Subsequently computation and statistical processing of kinematic and dynamic parameters are made in the selected velocity windows. The main procedures for the algorithm include tomographic recovery of wavefield parameters in the plane of extraction panel, detection and interpretation of anomalous zones based on the prediction criteria to determine type of the discontinuity. There is a good reason that tomography in the plane of extraction panel shall be made in velocity windows of the dedicated wavetrains step by step for the main informative parameters. Analysis of the velocity distribution for the amplitude module maximum provides high accuracy when it comes to detect anomalous zones. This parameter is marked by relative independence on chance factors. Analysis of typical wavetrain frequency shift is determining factor indicative not only of the discontinuity but also of its type. Recording of wavetrain amplitude distribution is characterized by high accuracy in terms of anomalous zone detection. However, recording is complicated by dependence on a host of chance factors. The other parameters have much lesser quality and can be used as auxiliary. The algorithm is implemented into software capable to computerize most time-consuming operations. Use of this algorithm is illustrated as a case study for the results of data analysis and interpretation for seismic exploration at 37К10-В longwall panel section in Kuzembaev Mine (Kazakhstan).
An algorithm for processing of crosshole seismic survey data enabling recognizing the type and evaluate the characteristics of geological anomalies using a system of criteria is described. As part of ...the algorithm, the procedures for creating a line certificate, calculating amplitude spectra, velocity spectra, velocity response spectra, filtering operation, and travel-time graph plotting are performed. Then calculation of kinematic and dynamic parameters in the selected velocity gates and statistical processing are performed. The fundamental algorithm procedures are tomographic determination of the wavefield parameters in the extraction panel plane, selection and interpretation of anomalous zones using prediction criteria for determining the dislocation type. It is shown that it is advisable to perform the tomographic determination of the wavefield parameters in the extraction panel plane in the velocity gates of the identified wave packets in sequence for the main informative parameters. Analysis of the amplitude modulus maximum velocity distribution provides high accuracy in terms of identifying anomalous zones. This parameter is relative independent of random factors. The analysis of the wave packet characteristic frequency offsetting is the only key source allowing judge both presence and type of dislocation. Analysis of the distribution of wave packet amplitudes is characterized by high accuracy in terms of identifying anomalous zones. However, its use is complicated by the dependence on many random factors. Other parameters have much less information content and can be used as auxiliary ones. The algorithm is implemented in the software enabling automating the most labor-intensive operations. Its use was illustrated by the example of the analysis and interpretation of the seismic study findings in longwall 37K10-V of the Kuzembaev Mine (Kazakhstan).
An experimental method is proposed for the creation of plasma optical waveguides at low electron densities. The method consists of creating a hollow neutral-hydrogen channel by means of fast local ...heating of a hydrogen volume by a needlelike electron beam, followed by laser ionization of the hydrogen to provide the plasma waveguide. Results of numerical simulations are presented which show that guiding with an axial electron density in the range of 10(17) cm-3 can be achieved with a matched spot size of 30 microm. Its application for laser wakefield acceleration of electrons is discussed. The method would enable guiding lengths up to 30 cm at maximal energies of accelerated electrons in the range 10-100 GeV.
Self-organizing 'neck'type instabilities in capillary discharges are believed to be responsible for the population inversion in vacuum ultraviolet (VUV) spectral region. Selective population of the ...lasing levels originates as a result of charge-exchange recombination of the hot plasma ions during their flow from 'necks' into the cold surrounding gas. We propose a new approach of the 'induced neck' exploiting the axially inhomogeneous shock wave, generated in a capillary with a special wall profile and with high discharge current time derivative (about 1012 A s-1). A series of experiments with argon filling of the profiled capillary tube were performed. Time resolved pinhole VUV images of the discharge volume demonstrate the presence of the hot and compressed plasma objects on the discharge axes. All of them reproducibly appear at the same time and strictly on the axis of the capillary, in accordance with the wall structure. The VUV spectra, emitted by the compressed plasma, indicate a rather high electron temperature (50-100 eV), which must be sufficient for the production of hot plasma outflow.
The design of the grazing-incidence spectrometer, in the scheme of which microchannel plates (MCPs) elastically bent along the Rowland circle are used, is described. This scheme allows one to improve ...the matching of the spatial resolution of the MCP and the real spectral structure as compared with the outof- Rowland recording. The performed tests demonstrated the fivefold increase in the spectral resolution of the spectrometer.
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