Formation of compression erosion plasma fluxes of a given composition in dense gases

This article presents the results of experimental investigations of compression erosion plasma fluxes of a given composition determined by the material of the internal electrode; the fluxes have been obtained for the first time in air at atmospheric pressure. It is shown that a compression erosion plasma flux possesses marked absorption in the visible spectral region. The basic thermodynamic parameters of these fluxes were determined with the use of a two-channel system of recording plasma radiation. Reported at the International Conference on Plasma Physics and Plasma Technologies, Minsk, September 15–19, 1997. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 229–233, March–April, 2000.     

Nonelectrical method of pumping solid-state lasers

An alternative, nonelectrical method for obtaining a dense radiating plasma and the possibilities of using this method to pump solid-state lasers are investigated. The plasma was obtained experimentally by heating the working gas in a two-stage ballistic plasmatron. A new device — a vortex chamber — is proposed for transferring energy into the plasmatron-laser system. Zh. Tekh. Fiz. 68, 67–70 (September 1998)     

A process of thermocline erosion on the Sicilian continental shelf

Summary We study a process of thermocline erosion measured in the Channel of Sicily in the period 16 November–December 1985. Evidence is presented that the transition from Summer to Winter stratification has been an impulsive process. We show that the erosion of the seasonal thermocline and the deepening of the surface mixed layer were stimulated by the action of two strong atmospheric perturbations. Possible relations between mixing events and internal wave breaking are discussed. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

CO2 laser-induced plasma CVD synthesis of diamond

2 laser maintenance of a stationary optical discharge in a gas stream, exhausting over a substrate into the air (laser plasmatron). Nano- and polycrystalline-diamond films were deposited on tungsten substrates from atmospheric-pressure Xe(Ar):H₂:CH₄ gas mixtures at flow rates of 2 ?/min. A 2.5-kW CO₂ laser focused beam produced plasma. The deposition area was about 1 cm² and growth rates were up to 30–50 μm/h. Peculiarities and advantages of laser plasmatrons are discussed. Received: 15 January 1998/Accepted: 16 January 1998     

A DC probe diagnostics for fast electron temperature measurements in tokamak edge plasmas

The tunnel probe is a new kind of Langmuir probe for use in the tokamak scrape-off layer. It provides simultaneous measurements of electron temperature and parallel ion current density with high frequency at the same point in space. We describe ongoing work to characterize the ion flows within the probe, and to calibrate the diagnostics using 2D kinetic simulations. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreus, Seitzerland, June 23–24, 2002.     

Study of an Underexpanded Plasma Jet II. Diagnostics with Microwaves

The properties of the plasma of an underexpanded jet in air were examined by optical and by probe methods as described in a previous paper (Contrib. Plasma Phys. 27 (1987) 203). The jet was produced by an erosion plasmatron with xenon-filling operating in a single-pulse regime. Now, independent measurements of the space-time development of the electron density by microwave interferometry are described. The results of cut-off and phase shift measurements are in agreement with those obtained by probe diagnostics.     

Dynamics of plasma formation during quasicontinuous laser irradiation of metals in high-pressure nitrogen atmospheres

This is a study of target destruction and the dynamics of surface plasma formation during the interaction of quasicontinuous laser radiation (λ = 1.06 μm, q = 1–7 MW/cm², τ ∼ 1.5 msec) with D16T duraluminum and bismuth in nitrogen atmospheres at pressures p = 1–20 atm. High speed photography and spectroscopy of the erosion plasma flare are used to determine the onset time for vaporization of the target, as well as the times of appearance of erosion and nitrogen plasmas for different gas pressures and laser energy fluxes q. The emergence of the plasma front from the vapor zone into the surrounding nitrogen is detected experimentally and the properties of the nitrogen plasma are studied.     

Soft diffraction at the LHC: a partonic interpretation

We present a ‘new generation’ model for high energy proton–proton ‘soft’ interactions. It allows for a full set of multipomeron vertices as well as for including multichannel eikonal scattering. It describes the behaviour of the proton–proton total, σ_tot, and elastic, dσ_el/dt, cross sections together with those for low- and high-mass proton dissociation. Although the model contains a comprehensive set of multipomeron diagrams, it has a simple partonic interpretation. Including the more complicated multipomeron vertices reduces the absorptive effects as compared to the predictions in which only the triple-pomeron vertex is considered. Tuning the model to describe the available ‘soft’ data in the CERN ISR–tevatron energy range, we predict the total, elastic, single- and double-diffractive dissociation cross sections at the LHC energy. An inescapable consequence of including multichannel eikonal and multipomeron effects is that the total cross section is expected to be lower than before: indeed, we find σ_tot≃ 90 mb at the LHC energy. We also present differential forms of the cross sections. In addition, we calculate soft diffractive central production.     

Surfactant sputtering

Sputter erosion of materials is among the most important techniques for fabricating advanced thin film coatings. Sputter processes are also of considerable relevance for surface polishing down to an atomic scale, nano-structuring of surfaces as dot and ripple patterns and micro-machining of materials using focused ion beams or reactive ion etching. We present a new, versatile sputter technique utilizing the steady state coverage of a substrate surface with up to 10¹⁶ cm⁻² of foreign or self atoms simultaneously during sputter erosion by combined ion irradiation and atom deposition. These surfactant atoms (surface active agents) strongly modify the substrate sputter yield on atomic to macroscopic length scales. Depending on the surfactant–substrate combination, the novel technique allows enhanced smoothing of surfaces, the generation of novel surface patterns and nanostructures and the controlled shaping of surfaces on the nanometer scale. We present selected examples of surface morphology evolution, smoothing of surfaces and shaping of surfaces to demonstrate the capabilities of the new surfactant sputtering technique.     

Backscattering at the <Emphasis Type="Italic">E</Emphasis> and <Emphasis Type="Italic">F</Emphasis> layers for the vertical incidence of radio waves on the ionosphere

We present the results of the vertical ionosphere sounding at a frequency of 9.02 MHz using the “Sura” facility. Intense backscatter signals from meteor trails were observed at altitudes 100–130 km. Increased background of the scattered signal, which was about − 100 dB with respect to the mirror-reflected signal, was observed at altitudes of about 190–200 and 270–280 km. According to the Doppler-shift measurements of the scattered-signal frequency, the wind velocity was more than 30 m/s at altitudes 100–130 and 270–280 km and was significantly smaller in the altitude range 190–200 km. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 1, pp. 23–27, January 2009.     

Hard X-ray bursts and DD microfusion neutrons from complex plasmas of vacuum discharge

We create the random complex media of high-power density in low-energy nanosecond vacuum discharges. Hard X-ray emission efficiency, generation of energetic ions (∼1 MeV) and neutrons, trapping and releasing of fast ions and/or X-rays from interelectrode aerosol ensembles are the subject of our study. The neutrons from DD microfusion, as well as the modelling of some interstellar nuclear burning due to microexplosive nucleosynthesis are discussed. The value of neutron yield from DD fusion in interelectrode space varies and amounts to ∼10^{5–10 7}/4π per shot under ≈ 1 J of total energy deposited to create all discharge processes Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Influence of radial electric field on trajectories of plug potential bounce ion in the tandem mirror

Bouncing ions between the plug potentials play an important role in improvement of the axial confinement in the tandem mirror. We examined the influence of the radial electric field on the trajectories of the ions passed through the anchor cell with nonaxisymmetric magnetic configuration on the assumption that the shape of the magnetic flux tube was shifted from the shape of the equipotential surface of the plasma at the mirror throats of the anchor cells. The discrepancy between the shapes enhanced the radial drift of the bounce ion. Radial potential profile of the core plasma was controlled by adjustment of the radially separated endplate potentials, and it was found that the flattened radial potential profile was effective for the decrease of the radial drift. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreux, Switzerland, June 23–24, 2002.     

Lateral field instability and six-wave mixing in a diode laser with broad active area

The electromagnetic field inside a nonlinear active medium of a laser is considered as a system of counterpropagating waves. Such an approach changes radically an earlier studied behavior of the lateral field instability due to self-deformaion (or self-focusing). In our calculations we used an expression for a laser field in the form of two “strong” counterpropagating waves whose complex amplitudes have weak perturbations. Amplitude perturbations of each of the “strong” waves can be presented by two spatial harmonics corresponding to two weak perturbation waves with wave vectors making some tilted angle ±φ with the cavity axis. Thus six waves would participate in the interaction: two counterpropagating strong waves and two pairs of weak waves. Using this approach, we have developed a theory for the propagation of four “weak” perturbation waves in a nonlinear amplifying medium in the presence of two counterpropagating “strong” waves. It is shown that perturbation waves with tilted angle φ⋍0.5–1.2° inside the active region, and respecively, with the side lobes of the far-field pattern at ∼1.7–4°, have the greatest growth increment. These perturbation waves produce lateral intensity modulation with period 10–30 μm for the 0.85 μm lasing wavelength. The appearance of such waves corresponds to the instability threshold of a homogeneous lateral distribution of optical power in a diode laser. The present theory makes it possible to investigate the stability of the homogeneous lateral optical intensity distribution in a diode laser of any design. This allows one to choose a suitable design of a laser with a homogeneous lateral distribution at high radiation power. Translated from Preprint No. 43 (1992) of the Lebedev Physics Institute, Russian Academy of Sciences.     

Silicon-tungsten calorimeter for the forward direction in the PHENIX experiment at RHIC

The PHENIX detector at RHIC has been designed to study hadronic and leptonic signatures of the Quark Gluon Plasma in heavy ion collisions and spin dependent structure functions in polarized proton collisions. The baseline detector measures muons in two muon spectrometers located forward and backward of mid-rapidity, and measures hadrons, electrons, and photons in two central spectrometer arms, each of which covers 90. in azimuth and 0.35 units of rapidity. Further progress requires extending rapidity coverage for hadronic and electromagnetic signatures by upgrading the functionality of the PHENIX muon spectrometers to include photon and jet measurement capabilities. Tungsten calorimeters with silicon pixel readout and fine transverse and longitudinal segmentation are proposed to attain this goal. The use of such a design provides the highest density and finest granularity possible in a calorimeter. for the PHENIX Forward Calorimeter Collaboration Presented in the Poster Session “Future Experiments and Facilities” at the 18th International Conference “Quark Matter 2005”, Budapest, Hungary, 4–9 August 2005.     

Projective Invariance in Cosmological Models and Dark Energy

We study theories of gravitation that are based on the Einstein – Hilbert action that are not projectively invariant and can therefore completely determine their connections. We are thus lead to the conclusion that the geometry is necessarily Riemann – Cartan and at least the trace part of a torsion field must be present. We examine the consequence of including these torsion fields in cosmological models. Our results differ from those obtained earlier in the Einstein – Cartan – Sciama – Kibble theory. We also consider a model that includes a series of quadratic torsion terms. This series leads to a potential function that has the effect of “turning on” the cosmological constant. This potential function then acts like dark energy. This model also shows that the torsion field can produce an inflationary period. PACS: 04.02 Cv, 95.30 Sf, 98.80-k     

Mirror objectives with variable focal length

We consider some issues involved in constructing a mirror system with a discrete variable focal length. We propose a procedure for designing two-mirror pancratic (zoom) systems with fixed image plane. In constructing the optimal layouts, we studied a basic two-mirror system to achieve minimum spherical aberration. We present the calculated design characteristics of an objective consisting of two spherical mirrors and providing a three-fold variation in focal length. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 453–459, May–June, 2009.     

Drell–Yan diffraction: breakdown of QCD factorization

We consider the diffractive Drell–Yan process in proton–(anti)proton collisions at high energies in the color dipole approach. The calculations are performed at forward rapidities of the leptonic pair. The effect of eikonalization of the universal “bare” dipole–target elastic amplitude in the saturation regime takes into account the principal part of the gap survival probability. We present predictions for the total and differential cross sections of the single-diffractive lepton-pair production at RHIC and LHC energies. We analyze implications of the QCD factorization breakdown in the diffractive Drell–Yan process, which is caused by a specific interplay of the soft and hard interactions, resulting in rather unusual properties of the corresponding observables.     

Determination of reference values for optical characteristics in multiwavelength optical detection and ranging (lidar) measurements of atmospheric extinction coefficients

We have studied multiple regressions between the spectral aerosol extinction coefficient ε, backscatter indicatrix g_π, and light-scattering coefficients β_θ at angles of θ = 1–180°, which we used to select the optimal scattering angle for determining the extinction coefficient at the wavelengths 0.350, 0.532, and 1.060 μm. We have estimated the errors in determination of the values of ε and g_π at the given wavelengths for different atmospheric situations with different meteorological parameters. We have shown that it is possible to use the spectral β_θ values at a 33° angle to determine the reference values for ε(λ) and g_π(λ) at λ = 0.350, 0.532, and 1.060 μm in laser detection and ranging (lidar) measurements, and we give examples of recovering the vertical profiles of ε in a slightly turbid atmosphere from the results of simultaneous multiwavelength lidar and nephelometric measurements. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 767–772, November–December, 2007.     

Infinite slabs and other weird plane symmetric space–times with constant positive density

We present the exact solution of Einstein’s equation corresponding to a static and plane symmetric distribution of matter with constant positive density located below z = 0. This solution depends essentially on two constants: the density ρ and a parameter κ. We show that these space–times finish down below at an inner singularity at finite depth. We show that for κ ≥ 0.3513 . . . the dominant energy condition is satisfied all over the space–time. We match this solution to the vacuum one and compute the external gravitational field in terms of slab’s parameters. Depending on the value of κ, these slabs can be attractive, repulsive or neutral. In the first case, the space–time also finishes up above at an empty repelling singular boundary. In the other cases, they turn out to be semi-infinite and asymptotically flat when z → ∞. We also find solutions consisting of joining an attractive slab and a repulsive one, and two neutral ones. We also discuss how to assemble a “gravitational capacitor” by inserting a slice of vacuum between two such slabs.     

Fast primary store based on an Arkad’ev-Marx generator

We describe the design of an Arkad’ev-Marx generator with the capacitors discharging energy into the magnetic field within a time less than 1 μsec. We give the equivalent circuit of the generator and calculations for the transient for different firing circuits. We present the results of an experimental study of a generator consisting of 10 stages. Institute of High-Current Electronics, Siberian Branch, Russian Academy of Sciences. Centre d’Etudes de Gramat, France. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 17–24, December, 1997.