Dual-jet plasmatron for medical applications

We present a design for a dual-jet arc plasmatron operating at a frequency of 66 kHz in an argon flow at atmospheric pressure. We present the results of determination of the temperature, electron concentration, and electrode erosion obtained by atomic emission spectral analysis. The proposed convenient design for a dualjet plasmatron and the low erosion of the copper electrodes in the plasma make it possible to use it for medical purposes. Report given at the Fifth International Conference on Plasma Physics and Plasma Technologies (PPPT-5), 18–22 September 2006, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 139–140, January–February, 2007.     

Dynamics of erosion plasma formation and formation of a plasma flame with a condensed disperse phase when quasi-continuous laser radiation acts on bismuth

The dynamics of near-surface plasma formation and the formation of an erosion plasma flame was investigated for quasi-continuous laser radiation (λ=1.06 μm, q=0.1–10 MW/cm², τ∼1.5 msec) acting on bismuth targets in air. The absence of low-threshold plasma formation at q<2 MW/cm² was established and explained. Instabilities in the plasma formation were revealed and the range of laser radiation power densities (2≤q≤4 MW/cm²) at which these instabilities take place was determined. At q≥5.4 MW/cm², brightening of the flame was noted. The dependence of the luminescence temperature of the flame on the laser radiation power density q was determined. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 126–133, January–February, 1998.     

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.     

Shaping dynamics and structure of large-scale surface plasma formations under single-pulse laser action on various materials

It is established that, in the case of laser action on materials in large illuminated spots in atmospheric-pressure air for a laser radiation power density q≤2 MW/cm² (λ=1.315 μm), an evaporative regime with plane scattering of the laser-produced erosion plasma is realized while, for q≈5–17 MW/cm², the plasma front is transferred to the air, leading to plasma screening of the target and shaping of a subsonic radiation wave in the air. As the duration of the laser pulses increases (τ∼160 μsec), in spite of the large illuminated spots (S∼150 cm²) the evaporative regime of the laser action with plane plasma scattering goes over into a regime with jet outlow and formation of a quasistationary shock wave. Deceased. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 261–268, March–April, 1998.     

Spectral-time characteristics of combined-target laser plasma

From the analysis of the contours of the spectral lines of target-material atoms, the electron and atomic concentrations and their variation with time are determined in the laser plasma of a combined Cu–Al–Cu target. The time dependences for the concentrations of electrons and atoms in the ground and excited states are explained within the framework of a model that allows for plasma decay being determined by processes of three-particle recombination and ionization as well as by the variation in the particle concentration in plasma expansion. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 426–432, May–June, 1998.     

Laser absorption and fluorescence diagnostics of a plasma

Diagnostics of a near-surface laser plasma, the plasma of a strong-current pulse gaseous discharge in inert gases, nitrogen, and carbon dioxide under conditions of intense evaporation of the wall of the discharge chamber, the plasma of a discharge with a hollow cathode, and the active medium of an excimer laser was conducted by methods of intracavity laser spectroscopy and laser-induced fluorescence. The dynamic fields and absolute concentrations of atoms, ions, molecules and electrons, the plasma temperature, and the velocities of flows of particles were measured. The quantitative determination of the density of particles in the erosion laser flame prior to breakdown and the phenomena associated with the formation of molecules in the laser plasma received primary consideration. To whom correspondence should be addressd. Instite of Molecular and Atomic Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 281–290, May–June, 1997.     

Fluorescence assay of tyrosine in blood plasma

A more simple and sensitive assay for the quantitative determination of tyrosine in blood plasma is developed on the basis of a modification of the method of S. Udenfriend (1962). A volume of 0.2 ml of plasma is used in the analysis; after its deproteinization with trichloroacetic acid, it is reacted with sodium nitride, nitrous acid, and 1-nitroso-2-naphthol at 65°C, and the content of the reaction product is measured by the fluorescence at λ_ex/λ_em=460/570 nm. The consumption of plasma and reagents is reduced by a factor of 5–10 compared to the original method; in addition, the stage of extraction with an organic solvent is excluded. The linear dependence of the fluorescence signal on the tyrosine concentration within the range of 2–60 μg/ml, high specificity, accuracy, and reproducibility of the assay are shown. The importance of tyrosine determination in monitoring of glucocorticoid therapy and protein catabolism is discussed. Institute of Photobiology, National Academy of Sciences of Belarus, 27, Akademicheskaya St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 366–371, May–June, 1998.     

Influence of peripheral radial electric field on L-H transition in T-10 tokamak

In this paper the peripheral plasma behaviour during and after L-H transition on the tokamak T-10 is considered. Abrupt changes of Scrape-Off Layer (SOL) plasma parameters (ion saturation current, floating potential, electron temperature) are observed in regimes with transition to the improved plasma confinement. Such changes begin (5–150) ms prior to the L-H transition. The time delay of a transition depends on auxiliary plasma heating powerP _aux and plasma currentI _p (at constant toroidal magnetic field inductionB _t). Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000. This work is supported by Ministry of Atomic Energy of Russia (contract 69F) and by Ministry of Science and Technology of Russia (Federal Program “Controlled Thermonuclear Fusion and Plasma Processes”).     

The effect of the use of different electrode materials for edge-plasma biasing on plasma density and floating potential modifications

The effect of the use of different electrode materials for edge-plasma biasing on plasma density and floating-potential profile modifications has been recently investigated on the CASTOR tokamak. Dependences of biasing current, edge plasma density and floating potential on biasing voltage have been measured. Induced relaxation events and fast (10–50) kHz oscillations are shown and surface changes of the biasing electrodes are discussed in the paper. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005.     

Phase formation and structural changes in the chromium-silicon system exposed to compressed plasma fluxes

The results of the study of structural and phase transformations in the silicon substrate-chromium coating system exposed to compression plasma fluxes with power densities of 0.3–1.2 GW/m² are discussed. The formation of hexagonal chromium disilicide and an amorphous phase, the growth of silicon dendrites, and the appearance of a chromium-enriched near-surface layer are revealed effects. The mechanisms of structural and phase transformations caused by rapid cooling of a mixed melt and concentration overcooling during solidification are analyzed.     

Formation of excited states of atoms and ions in laser plasma from CuInS2

Emission spectra and the energy distribution of the excited-state population density of atoms and ions in erosion laser plasma from CuInS₂ with various crystal-structure orderings are analyzed. It is shown that increased ordering of the target crystal structure causes the excited-state energies of indium atoms generated in the laser erosion plume to increase and that sulfur atoms always emit only in transitions from highly excited states. The ratio of relative ion concentrations in the laser plasma plume is Cu⁺/In⁺/S⁺ = 0.3/0.08/2, which corresponds neither to the atomic ratio of Cu/In/S (1/1/2) in the target nor to the ratio of ionization energies. The results are explained by recombination processes for ions and by the atomization specifics of the CuInS₂ target exposed to long-wavelength radiation. The atomization consists essentially of dissociative processes expressed by CuInS₂ → CuInS + S and CuInS₂ → Cu + InS + S. The electron temperature of polycrystal (single-crystal) plasma at a distance of 1 mm from the target is 0.3 eV (0.4 eV) for atoms and 1.3 eV (2.7 eV) for ions and varies negligibly for plasma up to a distance of 7 mm from the target. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 217–223, March–April, 2008.     

Parametric instabilities in magnetized bi-ion and dusty plasmas

The excitation of low frequency modes of oscillations in a magnetized bi-ion or dusty plasma with parametric pumping of the magnetic field is analysed. The equation of motion governing the perturbed plasma is derived and parametrically excited transverse modes propagating along the magnetic field are found. With multiple ion species or charged dust present, a number of different circularly polarized modes can be excited. The stability of these modes is investigated as a function of the plasma parameters. The modulational instabilities of large amplitude normal modes, modified by the extra ion species or dust and propagating along the magnetic field, are also investigated Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Synthesis of nanoparticles in an atmospheric pressure glow discharge

Nanopowders are produced in a low temperature, non-equilibrium plasma jet (APPJ), which produces a glow discharge at atmospheric pressure, for the first time. Amorphous carbon and iron nanoparticles have been synthesized from Acetylene and Ferrocene/H₂, respectively. High generation rates are achieved from the glow discharge at near-ambient temperature (40–80°C), and rise with increasing plasma power and precursor concentration. Fairly narrow particle size distributions are measured with a differential mobility analyzer (DMA) and an aerosol electrometer (AEM), and are centered around 30–35 nm for carbon and 20–25 nm for iron. Particle characteristics analyzed by TEM and EDX reveal amorphous carbon and iron nanoparticles. The Fe particles are highly oxidized on exposure to air. Comparison of the mobility and micrograph diameters reveal that the particles are hardly agglomerated or unagglomerated. This is ascribed to the unipolar charge on particles in the plasma. The generated particle distributions are examined as a function of process parameters.     

Parameters of free-burning arc discharge plasma in air with silver-based electrodes

We have used optical spectroscopy to study the radial temperature profiles for an electric arc plasma between silver electrodes and electrodes made from composite materials based on silver (Ag-CdO). We studied the structural changes in the working layers of the electrodes by metallography. We established that the parameters of the arc discharge plasma are determined by the condition of the electrode surface. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 375–379, May–June, 2006.     

Effect of ionized plasma medium on the radiation from a RITMA structure on ferrite substrate

This paper presents theoretical investigations on the radiation properties of a right isosceles triangular microstrip antenna (RITMA) printed on a magnetized ferrite substrate Ni_0.62Co_0.02Fe_1.948O₄ in the presence of ionized plasma medium. The theoretical study on RITMA structure in free space is carried out in TM₁₁ mode of excitation by applying cavity model-based modal expansion technique while hydrodynamic theory is used for its analysis in plasma medium. By varying the bias magnetic field, far-field radiation patterns in free space and plasma medium are obtained which in turn are applied in computing radiated power, directivity, quality factor and bandwidth of antenna. It is found that the presence of plasma medium affects the performance of RITMA structure significantly Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

Investigation of Saha-Boltzmann equilibrium in the analyte zone of a two-jet plasma generator

Relative populations of the excited levels for Cr(I), Cr(II), Fe(I) and Fe(II) in the argon plasma flow of an arc two-jet plasma generator used in spectrochemical analysis were measured. The range of the total energy E of excitation and ionization was 4.5–8.0 and 12.5–16.0 eV, respectively. It is shown that the populations of atom and ion levels are linear with respect to energy lower than E∼15 eV. For ionic lines with energy close to 15.5–16.0 eV the line intensities behave anomalously against equilibrium values. This can be associated with charge transfer between the analyte and argon ions. Deviation of I from LTE values increases in the plasma zones below and above the site of jet confluence, where the plasma temperature decreases. A. P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, 1a Favorskii St., Irkutsk, 664033, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 575–581, September–October, 1997.     

Measurements of plasma temperature and electron density in laser-induced copper plasma by time-resolved spectroscopy of neutral atom and ion emissions

Plasma produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a copper solid sample in air at atmospheric pressure is studied spectroscopically. The temperature and electron density characterizing the plasma are measured by time-resolved spectroscopy of neutral atom and ion line emissions in the time window of 300–2000 ns. An echelle spectrograph coupled with a gated intensified charge coupled detector is used to record the plasma emissions. The temperature is obtained using the Boltzmann plot method and the electron density is determined using the Saha-Boltzmann equation method. Both parameters are studied as a function of delay time with respect to the onset of the laser pulse. The results are discussed. The time window where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the laser-induced breakdown spectroscopy (LIBS) analysis of samples, is deduced from the temporal evolution of the intensity ratio of two Cu I lines. It is found to be 700–1000 ns.     

Plasma treatment of polyester fabric to impart the water repellency property

Polyester fabric is treated with DCDMS solution by two methods: dipping the fabric directly in DCDMS solution for different intervals and dipping the fabric in DCDMS solution after its exposure into RF plasma chamber for different durations at optimized exposure power conditions. The physical properties of polyester fabric treated with DCDMS in the presence or absence of air plasma have been compared with control fabric. Different characterization techniques like scanning electron microscope, attenuated total reflectance-IR and Dataflash 100 colour measurement spectrophotometer are used to assess the surface morphology, composition and change in colour parameters. Water repellency property of both untreated and modified polyester fabric is studied using AATCC test method 39 (1971). The effectiveness of the water repellency property of modified polyester fabric is checked by repeated washing up to ten cycles. This article was presented at the Second International Conference on the Frontiers of Plasma Physics and Technology, 21–25 February 2005, Goa, India.     

Multifractal analysis of plasma turbulence in biasing experiments on Castor tokamak

Experiments as well as some stochastic models have shown that behaviour of the transport in the edge plasma in fusion devices should be considered as a multi-scale phenomenon. The multifractal statistics describes processes as a multiplicative cascade with a complex self-similarity. The multifractal analysis, which enables to clearly demonstrate the turbulent properties of plasma, was applied to fluctuating signals in the biasing experiments. The influence of the biasing parameters is shown. A comparison with other types of the analysis is illustrated, too. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005.     

Target plasma formation by UHF power

The properties of plasma injected into an open magnetic trap of uniform field from an independent UHF source have been investigated. Plasma is created in the UHF source at the frequency of 2400 MHz (power input 150 W) in the electron cyclotron resonance (ECR) regime at the pressure of neutral argon (10⁻⁵−10⁻²) torr. It is established that a rather quiescent target plasma with controlled density within the range of (2 × 10⁸−2 × 10¹²) cm⁻³ and temperature 2–3eV is accumulated in the trap. It turned out that plasma lifetime in the trap is determined by a classical mechanism of particle escape at the expense of collisions, at fixed value of magnetic field in the trap it practically is not changed with the variation of neutral gas pressure and reaches the value ≈ 4×10⁻³ s at the magnetic field strength in the trap equal 1600 Oe.