Acta Polytechnica 2013/2
In memory of Alois Apfelbeck: An Interconnection between Cayley-Eisenstein-Pólya and Landau Probability Distributions
Vladimír Vojta
The interconnection between the Cayley-Eisenstein-Pólya distribution and the Landau distribution is studied, and possibly new transform pairs for the Laplace and Mellin transform and integral expressions for the Lambert W function have been found.
Keywords: Cayley-Eisenstein-Pólya distribution, Landau distribution, Lambert function, Laplace transform, Mellin transform, Mellin multiplier, Hadamard fractional integral, Liouville fractional integral.
Clock Math — a System for Solving SLEs Exactly
Jakub Hladík, Róbert Lórencz, Ivan Šimeček
In this paper, we present a GPU-accelerated hybrid system that solves ill-conditioned systems of linear equations exactly. Exactly means without rounding errors due to using integer arithmetics. First, we scale floating-point numbers up to integers, then we solve dozens of SLEs within different modular arithmetics and then we assemble sub-solutions back using the Chinese remainder theorem. This approach effectively bypasses current CPU floating-point limitations. The system is capable of solving Hilbert’s matrix without losing a single bit of precision, and with a significant speedup compared to existing CPU solvers.
Keywords: integer arithmetic, modular arithmetic, Hilbert’s matrix, error-free, GPGPU, solver, OpenCL, optimizations.
Fractal Dimension Estimation in Diagnosing Alzheimer’s Disease
Václav Hubata-Vacek, Jaromír Kukal, Robert Rusina, Marie Buncová
Estimated entropies from a limited data set are always biased. Consequently, it is not a trivial task to calculate the entropy in real tasks. In this paper, we used a generalized definition of entropy to evaluate the Hartley, Shannon, and Collision entropies. Moreover, we applied the Miller and Harris estimations of Shannon entropy, which are well known bias approaches based on Taylor series. Finally, these estimates were improved by Bayesian estimation of individual probabilities. These methods were tested and used for recognizing Alzheimer’s disease, using the relationship between entropy and the fractal dimension to obtain fractal dimensions of 3D brain scans.
Keywords: entropy, fractal dimension, Alzheimer’s disease, boxcounting, Rényi entopy.
A Study of Coherent Radiation Generated in an Ablative Capillary Discharge
Jakub Hübner, Pavel Vrba
Feasible soft-X-ray amplification in the CVI and NVII Balmer transition is investigated in a capillary discharge. The best conditions and parameters for the experimental set-up are found for an ablative capillary. The most optimistic results have shown that the gain would be greater than one, which is the condition for successful ASE (Amplified spontaneous emission) in capillary discharges. The capillary discharge evolution is modeled using the NPINCH program, employing a one-dimensional physical model based on MHD equations. The information about the capillary discharge evolution is processed in the FLY, FLYPAPER, FLYSPEC programs, enabling the population to be modeled on specific levels during capillary discharge.
Keywords: capillary discharge, XUV or soft X-ray laser, plasma modeling, ablation.
Characterization of Human Gait using Fuzzy Logic
Patrik Kutilek, Slavka Viteckova, Zdenek Svoboda
In medical practice, there is no appropriate widely-used application of a system based on fuzzy logic for identifying the lower limb movement type or type of walking. The object of our study was to determine characteristics of the cyclogram to identify the gait behavior by using a fuzzy logic system. The set of data for setting and testing the fuzzy logic system was measured on 10 volunteers recruited from healthy students of the Czech Technical University in Prague. The human walking speed was defined by the treadmill speed, and the inclination angle of the surface was defined by the treadmill and terrain slope. The input to the fuzzy expert system is based on the following variables: the area and the inclination angle of the cyclogram. The output variables from the fuzzy expert system are: the inclination angle of the surface, and the walking speed. We also tested the method with input based on the angle of inclination of the surface and the walking speed, and with the output based on the area and the inclination angle of the cyclogram. We found that identifying the type of terrain and walking speed on the basis of an evaluation of the cyclogram could be sufficiently accurate and suitable if we need to know the approximate type of walking and the approximate inclination angle of the surface. According to the method described here, the cyclograms could provide information about human walking, and we can infer the walking speed and the angle of inclination of the terrain.
Keywords: type of terrain, walking speed, inclination angle, fuzzy logic, cyclogram.
Predictive Models in Diagnosis of Alzheimer’s Disease from EEG
Lucie Tylova, Jaromir Kukal, Oldrich Vysata
The fluctuation of an EEG signal is a useful symptom of EEG quasi-stationarity. Linear predictive models of three types and their prediction error are studied via traditional and robust measures. The resulting EEG characteristics are applied to the diagnosis of Alzehimer’s disease. Our aim is to decide among: forward, backward, and predictive models, EEG channels, and also robust and non-robust variability measures, and then to find statistically significant measures for use in the diagnosis of Alzheimer’s disease from EEG.
Keywords: Alzheimer’s disease, EEG, linear predictive model, quasi-stationarity, robust statistics, multiple testing, FDR.
Multigroup Approximation of Radiation Transfer in SF6 Arc Plasmas
Milada Bartlova, Vladimir Aubrecht, Nadezhda Bogatyreva, Vladimir Holcman
The first order of the method of spherical harmonics (P1-approximation) has been used to evaluate the radiation properties of arc plasmas of various mixtures of SF6 and PTFE ((C2F4)n, polytetrafluoroethylene) in the temperature range (1000 ÷ 35 000) K and pressures from 0.5 to 5 MPa. Calculations have been performed for isothermal cylindrical plasma of various radii (0.01 ÷ 10) cm. The frequency dependence of the absorption coefficients has been handled using the Planck and Rosseland averaging methods for several frequency intervals. Results obtained using various means calculated for different choices of frequency intervals are discussed.
Keywords: SF6 and PTFE plasmas, radiation transfer, mean absorption coefficients, P1-approximation.
Development of the PETAL Laser Facility and its Diagnostic Tools
Dimitri Batani, Sebastien Hulin, Jean Eric Ducret, Emmanuel d’Humières, Vladimir Tikhonchuk et al.
The PETAL system (PETawatt Aquitaine Laser) is a high-energy short-pulse laser, currently in an advanced construction phase, to be combined with the French Mega-Joule Laser (LMJ). In a first operational phase (beginning in 2015 and 2016) PETAL will provide 1 kJ in 1 ps and will be coupled to the first four LMJ quads. The ultimate performance goal to reach 7PW (3.5 kJ with 0.5 ps pulses). Once in operation, LMJ and PETAL will form a unique facility in Europe for High Energy Density Physics (HEDP). PETAL is aiming at providing secondary sources of particles and radiation to diagnose the HED plasmas generated by the LMJ beams. It also will be used to create HED states by short-pulse heating of matter. Petal+ is an auxiliary project addressed to design and build diagnostics for experiments with PETAL. Within this project, three types of diagnostics are planned: a proton spectrometer, an electronspectrometer and a large-range X-ray spectrometer.
Keywords: plasma diagnostic, X-ray photon emission, proton radiography, particle laser acceleration, Laser MegaJoule, Petawatt laser, High Energy Density Physics, Electron spectrometer, X-ray spectrometer.
Computer Simulation of a Plasma Vibrator Antenna
Nikolay N. Bogachev, Irina L. Bogdankevich, Namik G. Gusein-zade, Vladimir P. Tarakanov
The use of new plasma technologies in antenna technology is widely discussed nowadays. The plasma antenna must receive and transmit signals in the frequency range of a transceiver. Many experiments have been carried out with plasma antennas to transmit and receive signals. Due to lack of experimental data and because experiments are difficult to carry out, there is a need for computer (numerical) modeling to calculate the parameters and characteristics of antennas, and to verify the parameters for future studies. Our study has modeled plasma vibrator (dipole) antennas (PDA) and metal vibrator (dipole) antennas (MDA), and has calculated the characteristics of PDAs and MDAs in the full KARAT electro-code. The correctness of the modeling has been tested by calculating a metal antenna using the MMANA program.
Keywords: computer simulation, plasma antenna, KARAT code, MMANA program.
The Process of Plasma Chemical Photoresist Film Ashing from the Surface of Silicon Wafers
Siarhei Bordusau, Siarhei Madveika, Anatolii Dostanko
At present, the research for finding new technical methods of treating materials with plasma, including the development of energy and resource saving technologies for microelectronic manufacturing, is particularly actual.In order to improve the efficiency of microwave plasma chemical ashing of photoresist films from the surface of silicon wafers a two-stage process of treating was developed. The idea of the developed process is that wafers coated with photoresist are pre-heated by microwave energy. This occurs because the microwave energy initially is not spent on the excitation and maintenance of a microwave discharge but it is absorbed by silicon wafers which have a high tangent of dielectric losses. During the next step after the excitation of the microwave discharge the interaction of oxygen plasma with a pre-heated photoresist films proceeds more intensively. The delay of the start of plasma forming process in the vacuum chamber of a plasmatron with respect to the beginning of microwave energy generation by a magnetron leads to the increase of the total rate of photoresist ashing from the surface of silicon wafers approximately 1.7 times. The advantage of this method of microwave plasma chemical processing of semi-conductor wafers is the possibility of intensifying the process without changing the design of microwave discharge module and without increasing the input microwave power supplied into the discharge.
Keywords: microwave plasma, microwave plasmatron, plasma chemical ashing of photoresist.
The Formation of a Power Multi-Pulse Extreme Ultraviolet Radiation in the Pulse Plasma Diode of Low Pressure
Ievgeniia V. Borgun, Mykola O. Azarenkov, Ahmed Hassanein, Oleksandr F. Tseluyko, Vasyl I. Maslov, Dmitro L. Ryabchikovk
In this paper results are presented on experimental studies of the temporal characteristics of spike extreme ultraviolet (EUV) radiation in the spectral range of 12.2 ÷ 15.8 nm from the anode region of high-current (I = 40 kA) pulsed discharges in tin vapor. It is observed that the intense multi-spike radiation in this range arises at an inductive stage of the discharge. It has been shown that the radiation spikes correlate with the sharp increase of active resistance and of pumped power, due to plasma heating by an electron beam, formed in the double layer of charged particles. It has been observed that for large number of spikes the conversion efficiency of pumped energy into radiationat double layer formation is essentially higher in comparison with collisional heating.
Keywords: EUV Sources, plasma discharge, Z–pinch, EUV radiation, conversion efficiency.
Growth and Physical Structure of Amorphous Boron Carbide Deposited by Magnetron Sputtering on a Silicon Substrate with a Titanium Interlayer
Roberto Caniello, Espedito Vassallo, Anna Cremona, Giovanni Grosso, David Dellasega, Maurizio Canetti, Enrico Miorin
Multilayer amorphous boron carbide coatings were produced by radiofrequency magnetron sputtering on silicon substrates. To improve the adhesion, titanium interlayers with different thickness were interposed between the substrate and the coating. Above three hundreds nanometer, the enhanced roughness of the titanium led to the growth of an amorphous boron carbide with a dense and continuing columnar structure, and no delamination effect was observed. Correspondingly, the adhesion of the coating became three time stronger than in the case of a bare silicon substrate. Physical structure and microstructural proprieties of the coatings were investigated by means of a scan electron microscopy, atomic force microscopy and X-ray diffraction. The adhesion of the films was measured by a scratch tester.
Keywords: boron carbide, magnetron sputtering, titanium, interlayer, scratch test.
Diffuse Coplanar Surface Barrier Discharge in Nitrogen: Microdischarges Statistical Behavior
Jan Cech, Jana Hanusova, Pavel Stahel, Pavel Slavicek
We studied statistical behavior of microdischarges of diffuse coplanar surface barrier discharge (DCSBD) operated in nitrogen atmosphere at two input voltage regimes. We measured spectrally unresolved discharge patterns together with discharge electrical parameters using highspeed iCCD camera and digital storage oscilloscope. External synchronization enabled us to measure the discharge pattern during positive and/or negative half-period of input high voltage in the single-shotmode of operation. The comparison of microdischarges behavior during positive, negative and both half periods of input high voltage was performed for two levels of input voltage, i.e. voltage slightly above ignition voltage and high above ignition voltage (“overvoltage”). The number of microchannels crossing discharge gap was counted and compared with number of microdischarge current peaks observed during corresponding half-period of input high voltage. The relations of those incidences was shown and discussed.
Keywords: DCSBD, diffuse coplanar surface barrier discharge, microdischarges, time resolved imaging, iCCD.
Local Magnetohydrodynamic Characteristics of the Plasma Stream generated by MPC
Tatyana N. Cherednychenko, Igor E. Garkusha, Vladimir V. Chebotarev, Dmytro G. Solyakov, Yuriy V. Petrov, Maryna S. Ladygina, Dmytro V. Eliseev, Alexander A. Chuvilo
This paper investigates the spatial distributions of electrical current which flows inside the plasma stream generated by a magnetoplasma compressor (MPC). Two different modes of MPC operation with different gas supply scenarios have been applied in the experiments presented here. The first is the operation mode with a pulse injection of xenon into the interelectrode space, and the second is the operation mode with residual helium in the chamber and local injection of xenon directly into the compression zone. The maximum value of the electric current observed outside the MPC channel is 15 ÷ 20% of the total discharge current. Electric current vortices were discovered in the plasma stream. The amplitude of the current in the vortices reaches 50% of the total discharge current. The maximum EUV radiation power was measured in the mode of MPC operation with local xenon injection. Power in the wave range 12.2 ÷ 15.8 nm achieves up to 16 ÷ 18 kW.
Keywords: magnetoplasma compressor, toroidal current vortices, plasma discharge.
The Construction of the Fast Resistive Bolometer for a SXR Measurement on the GIT-12 Facility
Jakub Cikhardt, Daniel Klír, Pavel Kubeš, Josef Kravárik, Karel Rezác, Ondrej Šíla, Alexander V. Shishlov, Alexey Yu. Labetsky
A lot of kinds of instruments are used for the SXR measurement at pulsed power facilities, but most of them are difficult to calibrate absolutely. For the determination of the energy of SXR radiated by the discharge on Z-pinches, it is possible to use the bolometer which can be calibrated analytically. The bolometer can be constructed with the sufficient sensitivity and, at the same time, with the time resolution in the order of nanoseconds. This bolometer was designed and constructed for the measurement on the 5MA facility GIT-12 at the Institute of High Current Electronics (IHCE) of the Siberian Branch Russian Academy of Sciences in Tomsk. The experiments on GIT-12 with the neon and deuterium gas-puff load were diagnosed by the copper bolometer with the time resolution of 4 ns and the sensitivity of 12 V cm2 J−1.
Keywords: bolometers, X-rays, Z-pinches, plasma diagnostics.
Thomson Parabola Spectrometer for Energetic Ions Emitted from Sub-ns Laser Generated Plasmas
Mariapompea Cutroneo, Lorenzo Torrisi, Lucio Ando’, Salvatore Cavallaro, Jiri Ullschmied, Josef Krasa, Daniele Margarone, Andreji Velyhan, Eduard Krousky, Miroslav Pfeifer
Laser-generated plasmas were obtained in high vacuum by irradiating micrometric thin films (Au, Au/Mylar, Mylar) with the Asterix laser at the PALS Research Infrastructure in Prague. Irradiations at the fundamental wavelength, 300 ps pulse duration, at intensities up to about 1016W/cm2, enabled ions to be accelerated in forward direction with kinetic energies of the order of 2 MeV/charge state. Protons above 2 MeV were obtained in the direction orthogonal to the target surface in selffocusing conditions. Gold ions up to about 120 MeV and 60+ charge state were detected. Ion collectors and semiconductor SiC detectors were employed in time-of-flight arrangement in order to measure the ion velocities as a function of the angle around the normal direction to the target surface. A Thomson parabola spectrometer (TPS) with a multi-channel-plate detector was used to separate the different ion contributions to the charge emission in single laser shots, and to get information on the ion charge states, energy and proton acceleration. TPS experimental spectra were compared with accurate TOSCA simulations of TPS parabolas.
Keywords: Thomson parabola spectrometer, high intensity laser, focal position, Opera 3D Tosca code, simulation.
Plasma–Surface Interactions Under High Heat and Particle Fluxes
Gregory De Temmerman, Kirill Bystrov, Feng Liu, Wei Liu, Thomas Morgan, Irem Tanyeli, Miranda van den Berg, Haiyan Xu, Jakub Zielinski
The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface interactions studies under those very harsh conditions. While the ion energies on the divertor surfaces of a fusion device are comparable to those used in various plasma-assited deposition and etching techniques, the ion (and energy) fluxes are up to four orders of magnitude higher. This large upscale in particle flux maintains the surface under highly non-equilibrium conditions and bring new effects to light, some of which will be described in this paper.
Keywords: plasma-surface interactions, refractory metals, carbon, linear plasma generator.
Inactivation of Candida albicans by Corona Discharge: The Increase of Inhibition Zones Area After Far Subsequent Exposition
Vladyslava Fantova, Karol Bujaček, Vítezslav Kříha, Jaroslav Julák
The cold atmospheric pressure plasma generated by the negative corona discharge has inhibition effect on the microorganism growth. This effect is well-known and it can be demonstrated on the surface of cultivation agar plates by the formation of inhibition zones. We exposed the cultures of Candida albicans to the negative corona discharge plasma in a special arrangement in this study: The equal doses of plasma were applied subsequently twice or four times on the same culture on one Petri dish, while the distance between exposed points was variable. Only small differences were observed in decontaminated zone areas for twice exposed agar at the shortest distance between exposed points (1.5 cm). In case of the four times exposed agars, we observed significant differences in inhibition zone areas, dependent not only on the exposition site distances, but also on the exposition order. The largest inhibition zone size was observed for the first exposition decreasing to the fourth one. To check relevancy of these dependencies, we presume to conduct further set of experiments with lower yeast concentration. In conclusion, significant difference in partial inhibition zone sizes appeared only when four expositions on one Petri dish were carried out, whereas no significant difference was observed for two subsequent expositions. The explanation of this effect may be the subject of subsequent remote exposition(s), when minute amounts of scattered active particles act on the previously exposed areas; the influence of diffused ozone may also take place.
Keywords: cold atmospheric plasma decontamination, Candida albicans, direct and indirect treatment.
Systems of Electronic Overcurrent Protection in Pulse Power Generator Operating on Plasma Load
Dmitriy V. Godun, Sergey. V. Bordusov, Anatoliy P. Dostanko
Schematic peculiarities of pulsed power source and modulator-shaper for working on high instability plasma load are discussed. In its construction should be provided for several levels of overcurrent protection. First of all modules of electronic protection should be integrated into the control driver system of IGBT modules and must provide a quick disconnect power switches in excess of the allowable values of pulse current. The next level of overcurrent protection in pulse power generator is a protection against overcurrent in the load circuit. Operating threshold of current protection in this case must be set to the maximum value of current in the secondary circuit. In order to limit the emission of stray voltage on the power pulses in a moment of switching of power switches a restrictive RC snubbers parallel to the collectors and the emitters of transistors must be installed. It is also appropriate application of software-controlled configurating of electrical power at the outputof a pulsed power supply.
Keywords: plasma, high-voltage source, pulse voltage.
Physical and Electrical Properties of Yttria-Stabilized Zirconia Thin Films Prepared by Radio Frequency Magnetron Sputtering
Dmitriy A. Golosov, Sergey M. Zavatskiy, Sergey N. Melnikov
This paper presents the electrophysical characteristics of a 7 mol.% yttria-stabilized zirconia (YSZ) thin film deposited by radio-frequency magnetron sputtering. In order to form the crystallinestructure, the deposited films were annealed in air over a temperature range of 700 ÷ 900 °C. By XRD analysis it was established that as the deposited films were amorphous, they crystallized into a pure cubic structure as a result of annealing in air at a temperature above 820 °C.The electrophysical properties of YSZ films were investigated on structures such¨as Ni/YSZ/Pt/Ti/Si and Ni/YSZ/Si. Film features ε > 20 and tg δ < 0.05 were obtained. An estimate of the capacity–voltage characteristic proved that the Ni/YSZ/Si structures possessed a hysteresis. This hysteresis resulted from the drift of the mobile ions in the YSZ film. High-temperature ionic conductivity of the stabilized zirconia was determined by the measurements of the electric resistivity of the YSZ films at 1 kHz over the temperature range from ambient to 800 °C. The YSZ film conductivity obtained was 1.96 × 10−2 S/cm under 800 °C.
Keywords: yttria-stabilized zirconia, RF sputtering, X-ray diffraction, dielectric constant, loss tangent, capacity-voltage characteristic, ionic conductivity.
The Research on Atmospheric Pressure Water Vapour Plasma Generation and Application for the Destruction of Wastes
Viktorija Grigaitiene, Andrius Tamošiunas, Pranas Valatkevičius
In the Lithuanian Energy Institute an experimental atmospheric pressure Ar/water vapour plasma torch has been designed and tested. The power of plasma torch was estimated 40 ÷ 69 kW, the mean temperature of plasma jet at the exhaust nozzle was 2300÷2900K. The chemical compositionof water vapour plasma was established from the emission spectrum lines at 300 ÷ 800nm range. The main species observed in Ar/water vapour plasma were: Ar, OH, H, O, Cu. The experiments on water vapour steam reforming were performed. The results confirmed that water vapour plasma has the unique properties – high enthalpy and environmentally friendly conditions. It could be employed for environmental purposes such as destruction of wastes into simple molecules or conversion to synthetic gas.
Keywords: water steam plasma, dc plasma torch, optical emission spectrum, waste treatment.
Proton- and -radiation of the Micro-Pinch with the Boron-Containing Target
Anatolii A. Gurin, Andrii S. Adamenko, Stanislav V. Adamenko, Mykola M. Kuzmenko
Using ion pinhole camera and track detectors, the image of hot spot is recorded in a pulsed diode micro-pinch equipped with a solid anode target. The track image is a record of repeated fronts of fast protons with energies up to 1 MeV. Fluctuations in the ion luminosity of hot spot are associated with the wave-like nature of the proton accelerating processes in the dense plasma of target material, which is characterized by a mean energy of 100 keV. The results of the track analysis of a fast ions, detected in the Thomson analyser in experiments with boron-polyethylene targets, are presented. In 5% of the shots, the presence of -particles of energy up to 2 MeV in the flux of fast ions is discovered by means of Thomson analyser equipped with track detectors. Estimations of total amount of helium nuclei as products of nuclear reactions p(B11, 2 ) result in an output of 108 ÷ 109 per successive shot.
Keywords: micro-pinch, fast ions, proton, boron, target, -particles.
Pin Hole Discharge Creation in Na2SO4 Water Solutions
Lucie Hlavatá, Rodica Serbanescu, Lenka Hlochová, Zdenka Kozáková, František Krčma
This work deals with the diaphragm discharge generated in water solutions containing Na2SO4 as a supporting electrolyte. The solution conductivity was varied in the range of 270 ÷ 750 μScm−1. The batch plasma reactor with volume of 100 ml was divided into two electrode spaces by the Shapal-MTM ceramics dielectric barrier with a pin-hole (diameter of 0.6 mm). Three variable barrier thicknesses (0.3; 0.7 and 1.5 mm) and non-pulsed DC voltage up to 2 kV were used for the discharge creation. Each of the current–voltage characteristic can be divided into three parts: electrolysis, bubble formation and discharge operation. The experimental results showed that the discharge ignition moment in the pin-hole was significantly dependent on the dielectric diaphragm thickness. Breakdown voltage increases with the increase of the dielectric barrier thickness.
Keywords: pin hole discharge, discharge in liquids, discharge breakdown.
Instability Growth Rate Dependence on Input Parameters During the Beam–Target Plasma Interaction
Miroslav Horký
The two-stream instability without magnetic field is described by the well-known Buneman dispersion relation. For more complicated situations we need to use the Generalized Buneman Dispersion Relation derived by Kulhánek, Bren, and Bohata in 2011, which is a polynomial equation of 8th order. The maximal value of the imaginary part of the individual dispersion branches ωn(k) is very interesting from the physical point of view. It represents the instability growth rate which is responsible for the turbulence mode onset and subsequent reconnection on the ion radius scale accompanied by strong plasma thermalization. The paper presented here is focused on the instability growth rate dependence on various input parameters, such as magnitude of a magnetic field and sound velocity. The results are presented in well-arranged plots and can be used for a survey of the plasma parameters close to which the strong energy transfer and thermalization between the beam and the target occurs.
Keywords: Buneman instability, numerical simulations, plasma, dispersion relation.
The Influence of Nitrogen in Ar+N2 Mixture on Parameters of High-Temperature Device with Electric Arc
Ivana Jakubova, Josef Senk, Ilona Laznickova
The paper presents the results of numerous experiments carried out on a high temperature device consisting of an arc heater with intensively blasted electric arc and reaction chambers connected to its output. The influence of nitrogen mass concentration (up to 11 %) in working gas Ar+N2 on voltage–current characteristics, power losses of individual parts and efficiency is studied for two variants of electrical configuration of the device. A short description of the computation of necessary thermodynamic and transport properties of Ar+N2 mixture is included. The computed properties are then used for evaluation of mean temperature and velocity at certain cross-sections of the device. Conclusions can be useful for the design of high temperature devices operating with argon/nitrogenmixture.
Keywords: arc heater, gas mixture, argon, nitrogen.
Calculation of the Inductance of Plasma Column at PF-1000 Device with Assumed Current Distribution
Jiri Kortanek, Pavel Kubes
Processed data is taken from the D−D fusion reaction experiments on PF-1000 at IFPILM Warsaw, operating with 2 MA, 1011 neutron yield, using interferometry, temporal resolved neutron diagnostics, magnetic probe diagnostics and X-ray diagnostics. The inductance is calculated under two different circumstances: with the known distribution function determined by the magnetic probe signal, and with the border of the plasma column determined from interferograms using Matlab. The inductance of the whole column is calculated using the formula for the inductance of a coaxial cylinder.
Keywords: nuclear fusion, plasma focus, pinch, inductance, diagnostics, Matlab.
Atmospheric Argon Free burning Arcs with a Simplified Unified Model Using CFD-Arc Modeling
Won-Ho Lee, Jong-Chul Lee
Free burning arcs, where the work piece acts as an anode, are frequently used for a number of applications. Our investigation is exclusively concerned with a simplified unified model of arcs and their electrodes under steady state conditions at atmospheric pressure. The model is used to make predictions of arc and electrode temperatures and arc voltage for a 200 A arc in argon. The computed temperatures along the axis between the cathode tip and the anode surface compare well the measured data.
Keywords: free burning arcs, thermal plasmas, arc modeling, arc-electrode interaction, computational fluid dynamics.
High-Speed Monitoring of Dust Particles in ITER ELMs Simulation Experiments with QSPA Kh-50
Vadym A. Makhlaj, Igor E. Garkusha, Nikolay N. Aksenov, Alexander A. Chuvilo, Igor S. Landman
Dust generation under powerful plasma stream impacts has been studied in ITER ELM simulation experiments with QSPA Kh-50 plasma accelerator. Repetitive plasma exposures of tungsten have been performed by 0.25 ms plasma pulses and the heat load varied in the range (0.1÷1.1) MJm−2. Main characteristics of dust particles such as a number of ejected particles, their velocity, angular distribution and start time from the surface are investigated. Dust particles have not been observed under heat load below the cracking threshold. Quantity of dust particles rises with increasing heat load. Average velocities of dust particles are found to be strongly dependent on their start time from the surface after beginning of plasma-surface interaction. Maximal velocity achieved a few tens of meters per second.
Keywords: ITER, ELMs simulation experiments, QSPA, plasma-surface interaction, tungsten dust.
Materials for Fusion Applications
Jiří Matějíček
An overview of materials foreseen for use or already used in fusion devices is given. The operating conditions, material requirements and characteristics of candidate materials in several specific application segments are briefly reviewed. These include: construction materials, electrical insulation, permeation barriers and plasma facing components. Special attention will be paid to the latter and to the issues of plasma-material interaction, materials joining and fuctionally graded interlayers.
Keywords: nuclear fusion, materials, plasma facing components, plasma-material interaction, functionally graded materials.
Long-Lived Plasma Process, Created by Impulse Discharge in Micro-Disperse Droplet Environment
Serge Olszewski, Tamara Lisitchenko, Vitalij Yukhymenko
The processes of organic compound (phenol and cation-active surfactants) destruction in water solutions, which stay under the influence of plasma treatment have been investigated in different dynamic plasma-liquid systems (PLS) with discharges in droplet micro-disperse environments (DMDE). The long-lived plasma process with separate spectral properties has been observed for pulsed discharge in DMDE. The approximate computer model is being proposed for a description of this effect. According to the introduced model this long-lived process is the aggregation of correlated discharges between charged droplets.
Keywords: dynamic plasma–liquid system, plasma-chemical processing, ultrasonic nebulization, droplet micro-disperse environment.
Velikhov Electrothermal Instability Cancellation by a Modification of Electrical Conductivity Value in a Streamer by Magnetic Confinement
Jean P. Petit, Jean C. Dore
We present a method, confirmed experimentally, allowing the cancellation of Velikhov instability by operating a local magnetic field reduction along a lane, which enhances local electric conductivity and electron-gas collision frequency, due to a local passage into a Coulomb collision regime and the subsequent lowering of the Hall parameter below its critical value, close to 2.
Keywords: non equilibrium plasmas, MHD, Velikhov instability.
Positioning of the Precursor Gas Inlet in an Atmospheric Dielectric Barrier Reactor, and its Effect on the Quality of Deposited TiOx Thin Film Surface
Jan Píchal, Julia Klenko
Thin film technology has become pervasive in many applications in recent years, but it remains difficult to select the best deposition technique. A further consideration is that, due to ecological demands, we are forced to search for environmentally benign methods. One such method might be the application of cold plasmas, and there has already been a rapid growth in studies of cold plasma techniques. Plasma technologies operating at atmospheric pressure have been attracting increasing attention. The easiest way to obtain low temperature plasma at atmospheric pressure seems to be through atmospheric dielectric barrier discharge (ADBD). We used the plasma enhanced chemical vapour deposition (PECVD) method applying atmospheric dielectric barrier discharge (ADBD) plasmafor TiOx thin films deposition, employing titanium isopropoxide (TTIP) and oxygen as reactants, and argon as a working gas. ADBD was operated in filamentary mode. The films were deposited on glass. We studied the quality of the deposited TiOx thin film surface for various precursor gas inlet positions in the ADBD reactor. The best thin films quality was achieved when the precursor gases were brought close to the substrate surface directly through the inlet placed in one of the electrodes.High hydrophilicity of the samples was proved by contact angle tests (CA). The film morphology was tested by atomic force microscopy (AFM). The thickness of the thin films varied in the range of (80 ÷ 210) nm in dependence on the composition of the reactor atmosphere. XPS analyses indicate that composition of the films is more like the composition of TiOxCy.
Keywords: AFM, atmospheric dielectric barrier discharge, chemical composition, chemical vapour deposition, inlet position, precursor gas, surface quality, thin film, TiOx, TiOxCy, XPS.
Estimation of Amount of Scattered Neutrons at Devices PFZ and GIT-12 by MCNP Simulations
Ondrej Šíla, Pavel Kubeš, Josef Kravárik, Karel Rezác, Daniel Klír, Jakub Cikhardt
Our work is dedicated to pinch effect occurring during current discharge in deuterium plasma, and our results are connected with two devices – plasma focus PFZ, situated in the Faculty of Electrical Engineering, CTU, Prague, and Z-pinch GIT-12, which is situated in the Institute of High Current Electronics, Tomsk. During fusion reactions that proceed in plasma during discharge, neutrons are produced. We use neutrons as instrument for plasma diagnostics. Despite of the advantage that neutrons do not interact with electric and magnetic fields inside device, they are inevitably scattered by materials that are placed between their source and probe, and information about plasma from which they come from is distorted. For estimation of rate of neutron scattering we use MCNP code.
Keywords: plasma focus, pinch effect, D−D reaction, MCNP.
X-ray Spectroscopic Characterization of Shock-Ignition-Relevant plasmas
Michal Šmíd, Luca Antonelli, Oldřich Renner
Experiments with multilayer plastic/Cu targets performed at a PALS laser system aimed at the study of matter at conditions relevant to a shock ignition ICF scheme, and, in particular, at the investigation of hot electrons generation. Plasma temperature and density were obtained using high-resolution X-ray spectroscopy. 2D-spatially resolved quasi–monochromatic imaging was observing the hot electrons via fluorescence K emission in the copper tracer layer. Found values of plasma temperature 690 ± 10 eV, electron density 3 × 1022 cm−3 and the effective energy of hot electrons 45 ± 20 keV demonstrate the potential of X-ray methods in the characterization of the shock ignition environmental conditions.
Keywords: hot electrons, shock ignition, laser-produced plasma, X-ray spectroscopy, K radiation.
Modification of Composite Material Fillers by Atmospheric Plasma Discharge
David Tichy, Pavlina Hajkova
This work is focused on the observation of the influence of cold atmospheric dielectric barrier discharge (DBD) on a modification of textile samples. The main objective of the experiment is to research wettability change of textiles modified by different exposure times and also the observation of the influence of a modification ageing effect. An ambient air was used as a working gas for DBD plasma. The wettability evaluation was carried out by a drop method, in which an imprint of the dropwas observed on the textile surface during various time intervals. An ageing effect of the modification was monitored within an interval of 28 days. Considerable increase of wettability of all modified samples has been proved. A fibre surface analysis was carried out by means of SEM.
Keywords: atmospheric plasma, dielectric barrier discharge, glass textiles, basalt textiles, wettability.
Nuclear Fusion Effects Induced in Intense Laser-Generated Plasmas
Lorenzo Torrisi, Salvatore Cavallaro, Mariapompea Cutroneo, Josef Krasa
Deutered polyethylene (CD2)n thin and thick targets were irradiated in high vacuum by infrared laser pulses at 1015W/cm2 intensity. The high laser energy transferred to the polymer generates plasma, expanding in vacuum at supersonic velocity, accelerating hydrogen and carbon ions. Deuterium ions at kinetic energies above 4 MeV have been measured by using ion collectors and SiC detectors in time-of-flight configuration. At these energies the deuterium–deuterium collisions may induce over threshold fusion effects, in agreement with the high D−D cross-section valuesaround 3 MeV energy. At the first instants of the plasma generation, during which high temperature, density and ionacceleration occur, the D−D fusions occur as confirmed by the detection of mono-energetic protonsand neutrons with a kinetic energy of 3.0 MeV and 2.5 MeV, respectively, produced by the nuclear reaction. The number of fusion events depends strongly on the experimental set-up, i.e. on the laser parameters (intensity, wavelength, focal spot dimension), target conditions (thickness, chemical composition, absorption coefficient, presence of secondary targets) and used geometry (incidence angle, laser spot, secondary target positions).A number of D−D fusion events of the order of 106÷7 per laser shot has been measured.
Keywords: D−D fusion, plasma laser, D−D cross section, proton detection, neutron detection.
Stimulated Raman Backscattering in Plasma — a Promising Tool for the Generation of Ultra-High Power Laser Beams
Hana Turčičová, Jaroslav Huynh
In the last fifteen years stimulated Raman backscattering (SRBS) in plasma has been intensively elaborated as a promising tool on the way towards high intense lasers. There are several advantages of this technique in comparison to the world-wide used the CPA-Chirped Pulse Amplification technique for a laser amplification. We present the principle of the SRBS technique, the best results so far obtained in theory and experiment, and a possible SRBS project at the PALS Research Centre in Prague.
Keywords: stimulated Raman scattering, laser plasma, high intensity lasers.
Ignition Features of Plasma-Beam Discharge in Gas-Discharge Electron Gun Operation
Valery A. Tutyk, Anatoliy N. Ovcharuk, Michail I. Gasik, Dmitriy V. Maslenikov
The current paper presents the results of experimental researches to determine the mode features of plasma-beam discharge (PBD) generation by an electron beam injected by a low-vacuum gasdischarge electron gun (LGEG) with the cold cathode and hollow anode on the basis of the high-voltage glow discharge and in the range of helium pressure of P 10 ÷ 130 Pa. The PBD boundaries and their dependences on parameters of an electron beam are found. The influence of PBD on parameters of low-vacuum gas-discharge electron gun is revealed. It causes an avalanche increase of electron beam current and burning of plasma-beam discharge in the whole space of the vacuum chamber volume and generation of electromagnetic radiation is revealed. Achieved results will be used for implementation of various vacuum technologies in the medium of reaction gas and generated electromagnetic radiation.
Keywords: plasma-beam discharge, vacuum, electron beam, electron gun, electromagnetic radiation.
Emittance Characterization of Ion Beams Provided by Laser Plasma
Luciano Velardi, Domenico Delle Side, Massimo De Marco, Vincenzo Nassisi
Laser ion sources offer the possibility to obtain ion beams useful for particle accelerators. Nanosecond pulsed lasers at intensities of the order of 108 W/cm2, interacting with solid matter in a vacuum, produce plasma of high temperature and high density. To increase the ion energy, an external post-acceleration system can be employed by means of high voltage power supplies of some tens of kV. In this work, we characterize the ion beams provided by an LIS source and post-accelerated. We calculated the produced charge and the emittance. Applying 60 kV of accelerating voltage and laser irradiance of 0.1 GW/cm2 on the Cu target, we obtain 5.5 mA of output current and normalized beam emittance of 0.2 mm mrad. The brightness of the beams was 137 mA (mm mrad)−2.
Keywords: LIS source, ion beam, emittance.