IEEE International Conference on Plasma Science

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  • ISSN
    0730-9244

Publications in this journal

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    ABSTRACT: form is given. This work considers the dynamics of long filamentary pulse discharge generated along the contact zone of two co-flown gases [1], basically: hydrocarbon fuel and oxidizer. The effect of the mixing actuation in compressible flow is observed because of the gas 863 dynamic instability arisen after the discharge generation. The mixing efficiency is examined qualitatively by means of Probe Discharge Breakdown Spectroscopy. An adequate measurement of the mixing efficiency is principally important for this study. The best way for that is to know the concentrations of main components and their spatial distribution. The idea is to realize breakdown of the so-called “probe” discharge that has much less power than the main one at some delay after the main breakdown and to analyze the spectrum of this probe discharge. The temporal resolution of this method is equal to the duration of probe discharge luminescence -
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 06/2013
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    ABSTRACT: form only given. Over the variety of available sensors dedicated to electric (E)-field characterization, the use of antennas constitutes the most widespread technique. While such probes are convenient and provide a good sensitivity, they remain invasive and bandwidth limited. At the opposite, fibered electro-optic transducers1 are fully dielectric, millimeter sized and allow to perform measurements of the E-field vector from DC to several gigahertz and even up to terahertz frequencies using equivalent-time sampling. Furthermore, recent developments lead to a simultaneous characterization of 2 transverse E-field vector components with a single EO probe2. Based on polarization state modulation, the EO transducer is linked to a remote (up to 30 meters) optoelectronic set-up including a ultra low noise laser feeding the probe and a real time optical set-up to manage the modulation treatment. The automated and servo controlled measurement bench is temperature dependent free. The available measurement dynamics exceeds 100 dB, ranging from less than 1 V. m-1. Hz-1/2 up to the breakdown electric field in air.An exhaustive comparison between BO sensors and other technologies will be firstly given during the conference. This analysis will be based on intrinsic sensor properties, such as sensitivity, frequency bandwidth, vectorial selectivity, spatial resolution and induced perturbation on the field to be measured. After recalling the principles of the BO effect, the optical arrangement of the optical probes will be described. The characterization of the BO system will be presented together with experimental results illustrating the potentialities of BO sensors. Among these examples, measurements of pulsed B-field in air (pulsed power), water (specific absorption rate evaluation in pulsed regime) or in plasma (real time evolution of the electrical discharge associated B-field) will be shown.
    IEEE Pulse Power and Plasma Science Conference, San Francisco – California – USA; 06/2013
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    ABSTRACT: This paper investigates the reaction of chloroform under non oxidative conditions in a quartz dielectric barrier discharge reactor. A non thermal plasma is generated in the dielectric barrier discharge reactor at atmospheric pressure where argon functions as a carrier gas and is mixed with chloroform and fed into the plasma zone. Parameters such as chloroform conversion, product distribution, reactor temperature and polymer characterisation are studied in this paper. A reaction mechanism outlining the reaction steps leading to the formation of major products is presented
    IEEE Pulsed Power and Plasma Science Conference; 06/2013
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    ABSTRACT: Spark gap switches are integral components in pulsed power applications ranging from pulsed microwaves and flash x-ray sources to, more recently, the linear transformer drivers (LTDs) powering next-generation petawatt-class pulsed power accelerators at Sandia National Laboratories (SNL) in Albuquerque, New Mexico. An LTD system uses a triggered switch to conduct current from two capacitors to form a magnetic field which accelerates particles down magnetically insulated transmission lines (MITLs). Existing spark gap switches suffer from limited lifetimes 1 and levels of jitter and inductance in excess of what will be required for these new accelerators2. Kinetech, under a contract from SNL, has designed, developed, and demonstrated a switch that exceeds all of the established requirements3 by firing for 57,200 shots with an inductance of 35 nH and a one-sigma switch jitter of 1.2 ns variation over a 1,000 shot sampling after 1k, 25k, and 50k shots. This paper will detail the design, development, and demonstration of this switch by Kinetech and SNL.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. The goal of streaked visible pyrometry experiments on Z is to determine the temperature of dynamic material samples using the Plank equation dL/dλ = ε 2hc2/λ5 (ehc/λkT-1) (1). The spectral irradiance dL/dl describes the amount of power emitted per unit area per unit solid angle per unit wavelength. Ideally, an absolute calibration is used to convert the measured signal such as CCD counts or film exposure to units of spectral irradiance (W/mm2/steradian/nm). Relative calibration, where measurements at different wavelengths are proportional to radiance by the same scaling factor can be useful for determining a “color” temperature. However, even at lower temperatures a relative measurement does not constrain the temperature as accurately as an absolute measurement. At higher temperature where there is little difference in the spectral irradiance at visible wavelengths, a relative calibration fails to constrain temperature at all. We have been unable to find a broadband calibration source that is bright enough to adequately expose our streaked pyrometer in a single step. Instead, this paper describes a multistage process for absolute calibration, taking care to link each stage into a complete calibration with minimum errors.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. Low surface energy of polymers is the chief obstacle to prevention of their wide application. Homogeneous non-thermal plasma at atmospheric pressure allows functional groups to be grafted on the surface of polymeric substrates, which is highly effective for the improvement in their printability and adhesion. We propose a dielectric barrier discharge (DBD) reactor consisting of two back-to-back L-shaped electrodes, driven by bipolar voltage pulses of opposite polarity. The discharge characteristics inside and outside the reactor are analyzed with the help of specifically designed reactor structure. The time-averaged image and temporal evolution of the discharge are taken by using an intensified charge-coupled device for different voltages. The discharge image is synchronized with the voltage-current waveforms by using the trigger pulse from the power supply. Finally, the applicability of the DBD reactor to the polymer surface treatment is discussed based on the experimental results.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. The stellarator Wendelstein 7-X, currently in its final construction phase at Greifswald, Germany, will employ a 10 MW, 140 GHz, continuous wave (CW) gyrotron-based electron-cyclotron resonance heating (ECRH) and-current drive (ECCD) system. To fulfill this demand for CW millimeter-wave power, Karlsruhe Institute of Technology (KIT) and Thales Electron Devices (TED, France) have been maintaining a successful series production of reliable megawatt-class 140 GHz gyrotrons throughout the last years, providing numerous opportunities for experimetal gyrotron research during the ongoing factory and site acceptance tests of the various tubes. Recently, a novel time-based pulse spectrum analysis system was developed at KIT, capable of recording time-dependent unambiguous frequency spectra with multiple GHz of instantaneous bandwidth in the millimeter-wave domain. Using this spectrum analysis system, the highly transient event of an RF arc at the dielectric microwave output window of a gyrotron in coincidence with a cavity mode switch was documented. It happened during experimental parameter-space exploration of W7-X series gyrotron SN5 in the KIT gyrotron test facility. In this report, co-simulations using the self-consistent slow-variables gyrotron interaction simulation code SELFT3 are presented, which aim at providing a deeper understanding of the mechanisms involved in the undesired event. Major focus is also placed on the similarities as well as differences between measured and simulated behavior, investigating the overall challenges and limitations of the undertaking.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. Atmospheric-pressure room-temperature plasma jets are commonly used in plasma medicine, nanotechnology, as well as surface and materials processing. Most of the applications require room-temperature operation while completely avoiding the glow-to-arc transitions. To meet these requirements, the atmospheric plasma jets are usually sustained in noble gases. However, this is very challenging for the open-air operation. Moreover, the cross-sections of the plasma plumes are typically very small, which make large-area surface processing particularly difficult. One promising way to overcome this shortcoming is by using the plasma jet arrays. However, since the individual plasma plumes generated by the arrayed plasma jets are in most cases independent and do not merge in open air, it is very difficult to achieve uniform plasmas and surface treatment effects. In this paper, we demonstrate a homogenous cold air plasma glow with a large cross-section generated by a direct current power supply. There is no risk of glow-to-arc transitions, and the plasma glow appears uniform regardless of the gap between the nozzle and the surface being processed. Detailed studies show that both the position of the quartz tube and the gas flow rate affect the plasma characteristics. Further investigation indicates that the residual charges trapped on the inner surface of the quartz tube may be responsible for the generation of the air plasma plume with a large cross-section. Moreover, the spatially resolved optical emission spectroscopy reveals that the air plasma plume is uniform as it propagates out of the nozzle. The air plasma plume with remarkable improvement of the plasma uniformity is used to improve the bio-compatibility of a glass coverslip over a reasonably large area. This improvement is demonstrated by a much more uniform and effective attachment and proliferation of human embryonic kidney 293 (HEK 293) cells on the plasma-treated surface.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: The electrical characteristics and current capabilities of a low inductance Marx generator used to drive a high power microwave (HPM) source are described. The operating frequency of many HPM sources is dependent upon various characteristics of the input voltage pulse from the pulsed power generator. Texas Tech University has developed an 8 stage, 80 J Marx generator used to drive HPM sources at repetition rates up to 500 Hz. The Marx generator is constructed using pulse forming networks rather than discrete capacitors. Experimental efforts have shown stable frequency operation of a virtual cathode oscillator (Vircator) source using a low energy, PFN Marx. Efforts were taken to reduce parasitic inductance of the PFN Marx resulting in a voltage pulse with a risetime less than 25ns with 50ns FWHM. Additionally, efforts were taken to improve impedance matching between the PFN Marx and the vircator load. This article presents experimental results of an 80 J Marx at voltages ranging from 150 kV to 250 kV operating in burst mode. Voltage and current waveforms from the Marx are shown as well as some typical results of compact sealed tube vircator operation.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. This work presents a novel theory of breakdown susceptibility for dielectric-loaded systems in DC, targeting multipactor as the lowest-order effect. Models from [1] are simulated with 2D particle-in-cell (PIC) using the method of [2], and susceptibility limits are developed employing the theory of [3]. Considering secondary electrons near the dielectric surface have a lifetime defined by the perpendicular (to the surface) electric field and an impact energy defined by the parallel field, a lower limit, (E⊥/E∥)1, and an upper limit, (E⊥/E∥)2, in E⊥/E∥-space can be formulated for multipactor in vacuum under quasi-static conditions neglecting space charge: (E⊥/E∥)1,2 = 2ν⊥0/(ν∥0-(√(2W1,2/me- -ν⊥02))) ν||0 and ν⊥0 are parallel and perpendicular initial velocities of an emitted secondary, respectively, and W1 and W2 are the first-crossover and second-crossover energies, respectively [3]. The evolution of the surface fields tracked via simulation can be plotted against these limits in E⊥/E||-space to determine multipactor-breakdown characteristics. The effects of secondary-emission energy and angle, applied voltage, space charge, and dielectric characteristics will be discussed. The effect of gases on susceptibility will also be discussed, targeting argon and air. As described in [4], gaseous breakdown in DC develops oscillatory behavior as a result of space-charge coupling between charged species and the charged dielectric surface. Near-surface ionization electrons will be involved in early-transient multipactor, influencing the drive to- saturation depending on impact characteristics. Increased pressure will non-linearly affect secondary impact characteristics as a result of increased space-charge and accelerated sheath formation. Gas species will also influence breakdown saturation and periodicity via interaction cross-sections, inertia, and drift characteristics via field interactions. Methods for incorporating these various parameters into the theory of susceptibility will be discussed.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: Literature indicates that introduction of Nano fillers into PP films will improve its electrical characteristics, such as the PD resistance, breakdown strength and loss factor [1]. Some dielectric properties of Nano filled polymers have shown remarkable improvements such as permittivity and space charge accumulation [2]. This research work investigates the effect of Nano fillers content on the PD resistance and Breakdown strength of the polypropylene films with 0%, 2% and 6% organoclay Nano fillers when the samples are subjected to Surface Discharges. The degree of erosion is quantified through microscopic and surface profilometer measurements that will help to figure out the resistance of the sample to surface discharges.
    Electrical Insulation Conference (EIC), 2013 IEEE; 01/2013
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    ABSTRACT: form only given. In his classic paper, Taylor [1] considered the instability on the surfaces of a fluid slab of a finite thickness that is accelerated by a much lighter fluid on either side of the fluid slab. The maximum number of e-foldings in the amplitude growth of the Taylor instability of this fluid slab is given by sqrt(2ks), where k is the wavenumber of the interface perturbation, and s is the distance traveled by the accelerated fluid slab, according to the linear theory. We show that this bound is independent of the magnitude and sign of the acceleration, of the magnitude and sign of the initial velocity of the slab, and of the width of the fluid slab. The primary dependence on the accelerated distance is illustrated in the resistive MHD radiation-hydrodynamics code, HYDRA [2], in which an aluminum slab with an initial sinusoidal surface ripple is accelerated by an intense magnetic pressure. Despite the nine times increase in magnetic pressure (from B = 200 T to 600 T), there is little difference in the Rayleigh-Taylor instability growth after the slab is accelerated for the same distance. This insensitivity to B appears to be the case in the simulation with or without the stabilization effect of the magnetic tension.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013
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    ABSTRACT: form only given. The ZaP Flow Z-pinch experiment1 at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Profiles of the plasma's axial flow are measured with a multi-chord ion Doppler spectrometer. A sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by the following diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density2; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements3; and fast framing photography for global structure. Recent experimental modifications demonstrate that the plasma lifetime appears to only be limited by plasma supply and current waveform. With a new gas injection configuration, stable plasmas persist for the duration of the current pulse. The flow Z-pinch concept provides an approach to achieve high energy density plasmas4 (HEDP), energy densities exceeding 1011 Pa, which are large, easy to diagnose, and persist for longer durations. A new experiment, ZaP-HD, will investigate this approach. Experimental plans and scaling analyses will be presented.
    Plasma Science (ICOPS), 2013 Abstracts IEEE International Conference on; 01/2013