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The influence of reflective Bragg gratings that are formed in an active medium due to the spatial periodic modulation of gain on the spectral properties of lasing are investigated by an example of a pulsed Nd : YAG laser. It is shown that, at a certain choice of the formation regime of reflective gratings of gain, the lasing bandwidth can be reduced by a factor of 3 – 5, with a corresponding increase in the pulse energy and significant improvement of spatial beam quality.

In the present paper, we experimentally study the diffusive dynamics in ensembles of self-propelled and self-rotating bristle-bots. Considering the dependence of the system dynamics on the packing density of robots as well as on the friction between individual robots, we show that the friction slightly affects the diffusive dynamics but leads to a significant change in the jamming transition corresponding to the formation of rigid clusters of robots.

Ce-doped (Pb, Gd)3(Al, Ga)5O12 single crystalline garnet films were grown using liquid-phase epitaxy method from supercooled PbO–B2O3-based melt solutions on substrates from Gd3Ga5O12 and Gd3Al2.26Ga2.74O12 single crystals. Optical absorption and photo- and cathodoluminescent properties of these epitaxial garnet films were studied. Ce-doped (Pb, Gd)3(Al, Ga)5O12 garnet films can be used as a fast phosphor in the design of a PIF-01 electron-optical converter.

In this paper, a study of composite materials based on ultrahigh molecular weight polyethylene (UHMWPE) and magnesium ferrite particles — precursors for electromagnetic shielding materials was carried out. Scanning electron microscopy, X-ray diffraction, Mossbauer and FTIR spectroscopy have been applied to study the influence of structural, morphological and magnetic state of ferrite particles on the composite polymer materials formed by the method of mechanochemical activation in mixtures of ferrites with UHMWPE. It was revealed that synthesis method type showed a significant effect on the size, morphology, crystal structure (inversion parameter) and magnetic properties of ferrite particles. All of these studied parameters determine their functional properties as an independent material, and their properties in the composition of the functional polymer composite material.

We present a detailed analysis of the spectrum of satellite transitions to the n = 23 and n = 2–4 Ne-like yttrium resonance lines. Satellite lines from the double excited 2s22p53l3l', 2s22p53l4l', 2s2p63l3l' and 2s2p63l4l' levels of Na-like Y as well as from 2s22p53l3l'3l" and 2s2p63l3l'3l" levels of Mg-like Y were observed in spectra from a laser-produced plasma. The x-ray spectra were recorded with high spectral resolution λ/Δλ ≈ 3500–5000 in the wavelength region of the n = 2–3 Ne-like resonance lines and with λ/Δλ > 1000 in the region of the n = 2–4 Ne-like resonance lines. A total of more than 50 spectral features were identified, and their wavelengths were measured. A simple intensity model was developed, which agreed well with the measured spectra and assisted the line identification. The consistency of the model for different spectral regions demonstrates the potential of the Na-like and Mg-like satellite lines for diagnosing plasma conditions.

X-Ray spectroscopy methods were used in an investigation of the spectra of plasmas formed from Mg, Al, Ge, Mo, and Ta targets by heating with iodine laser radiation of power density (3-5)x10{sup 14} W cm{sup {minus}2}. In the case of Ta targets the presence of Ta{sup 45+,46+} ions was detected. This information should help in the development of laser-plasma sources of multiply charged ions. The spectra were identified and the plasma parameters were measured. 18 refs., 4 figs., 3 tabs.

An investigation was made of a plasma formed by heating a gas target with neodymium gas laser radiation of ~15 GW power. The working substance was gaseous SF6. The x-ray emission spectra of sulfur and fluorine ions were investigated with one- and two-dimensional spatial resolution. These spectra were recorded by a high-resolution high-luminosity spectrograph with a mica crystal bent to form a sphere with a radius of R = 10 cm. Laser breakdown of a gas puff produced a sufficiently compact near-spherical plasma formation of ~2.5 mm size and with the electron temperature at least 470 eV.

We present an analysis of dielectronic satellite spectra of 2p6-2s2p63p Ne-like krypton resonance lines. The satellite structure was registered with high (better than ?/?? > 3500) spectral resolution in the emission of a laser irradiated gas puff target. We perform an unambiguous identification of satellite lines caused by radiative transitions from autoionizing states of sodium-like krypton ions. A total of about 20 spectral features are identified, most of them for the first time. Very good agreement between the satellite structure calculations and experimental emission spectra is obtained.

We present an analysis of dielectronic satellite spectra of Ne-like ion resonance lines for elements from Cr to Ni. For these low-Z elements, we use spectra from strongly underionized CO2-laser produced plasma to minimize the emission from open L-shell ions. This simplifies the spectra and allows the identification of satellite lines caused by radiative transitions from autoionizing states of sodium like ions. Good agreement between the satellite structure calculations and the experimental emission spectra is obtained.

Precision measurements were made of the wavelengths of the satellites of the resonance line of the H-like Mg XII ion as well as of a number of transitions in the Ne-like Ge XXIII ion and their satellites in a plasma created by radiation generated in an Nd-glass laser. The measurements were carried out with a high-resolution, high-luminosity spectrograph containing a mica crystal bent to a spherical surface with a radius R = 100 mm. The absolute wavelength obtained for the 2s22p6 1So—2s2p63p 3P1 transition in Ge XXIII was λ = 842.08 ± 0.09 pm. The results demonstrated that the short-wavelength component of the Lyman doublet of Mg XII (λ = 841.92 pm) could be used to pump optically a short-wavelength laser by transitions in the Ge XXIII ion.

A study has been made of the x-ray emission spectra of zinc ions (λ ~0.65–1.18 nm) excited in a plasma produced by the beam from a Nd laser. The wavelengths were measured within ±0.3 pm. The observed spectra have been identified. Detailed calculations have made it possible to identify, for the first time, some spectra lines due to the radiative decal of autoionizing states of Na-like zinc ions.

The properties of a magnesium plasma heated by picosecond laser pulses have been determined by x-ray spectral methods. Experiments were carried out at a laser power density ~ 1.5 1018 W/cm2. The x-ray spectra were detected by spectrographs with a plane CsAP crystal and a mica crystal bent into part of a spherical surface 10 cm in radius. The experimental data are compared with predictions of a calculation on the time-varying kinetics of multiply charged magnesium ions.

A high-transmission spectrograph equipped with a spherical mica crystal was used to study x-ray emission from an X-pinch plasma at high spectral (?/?? ~ 3000) and spatial (~30 ?m) resolutions. H- and He-like spectra of Al and Si ions generated in the X-pinch were detected both in the stage of maximum compression and in the dispersal stage. The electron temperature (up to 950 eV) and density (up to 2 ? 1024 cm?3 ) of the plasma at the hot point and also in the dispersal stage were measured by x-ray spectral methods. Energy estimates show that the radiation output in the K lines can reach 1 J (the corresponding power is 1 GW). The overall energy radiated in the wavelength region 0.5 to 10 nm is ~1 kJ. This result indicates that the radiation from the hot point of an X-pinch plasma can be an effective pumping source for the active medium of an x-ray laser. It also indicates that the recombining plasma dispersing out of the hot region can itself be used as an active medium for short-wavelength lasers.

A comparative analysis was made of the various methods for heating a laser plasma with Nd laser radiation. Methods of heating with the first and second harmonic pulses of different durations were compared. Diagnostics by x-ray spectroscopy yielded the parameters of a recombining plasma (temperature and density) and the populations of excited levels of the Al XII ion at different distances from the surface of an aluminum target. The experimental results on population inversion of the excited levels were compared with theoretical calculations.

Experiments are described in which a high-current electron accelerator is used to generate, by Al wire explosion, super-high-density (Ne=5*1022 cm-3), high-temperature (Te approximately=400 eV) plasmas. The X-ray emission characteristics of the plasma are analysed.

An experimental investigation was made of the expansion of an aluminum laser plasma into vacuum. X-ray spectral methods were used to determine the plasma parameters (temperature, density, and ionization state) and the ion distribution in terms of excited levels. A qualitative and quantitative interpretation of the experimental data is given and an estimate is obtained for the gains due to far ultraviolet (λ = 76–280 A) transitions in the Al XII ion.

An investigation was made of the formation of the active medium of a recombination laser utilizing the 4f–5g transition in the Be IV ion in an expanding laser plasma formed from a solid-state target. Spectroscopic methods were used to determine the electron density and temperature in the lasing zone. These parameters were used to find the gain due to the 4f–5g transition in the Be IV ion: at distances x 0.4 cm from the target the gain was 5 × 10 − 2–10 −1 cm −1. These values were close to the gain deduced experimentally from the threshold characteristics of the lasing process.