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14 Feb 2013

Volume 113, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 064301 (2013); http://dx.doi.org/10.1063/1.4789897 (11 pages)

Y. G. Marinov, G. B. Hadjichristov, A. G. Petrov, S. Marino, C. Versace, and N. Scaramuzza
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back to top Plasmas and Electrical Discharges

Joule heat generation in thermionic cathodes of high-pressure arc discharges

M. S. Benilov and M. D. Cunha

J. Appl. Phys. 113, 063301 (2013); http://dx.doi.org/10.1063/1.4790709 (11 pages)

Online Publication Date: 8 February 2013

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The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
84.47.+w Vacuum tubes
52.25.Mq Dielectric properties
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.40.Hf Plasma-material interactions; boundary layer effects
52.50.Lp Plasma production and heating by shock waves and compression

Deposition and tuning of nanostructured hydrocarbon deposits: From superhydrophobic to superhydrophilic and back

J. Berndt, H. Acid, E. Kovacevic, C. Cachoncinlle, Th. Strunskus, and L. Boufendi

J. Appl. Phys. 113, 063302 (2013); http://dx.doi.org/10.1063/1.4789949 (7 pages)

Online Publication Date: 11 February 2013

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Carbonaceous fluorine free nanoparticles synthesized in a low temperature acetylene discharge are used in a first step for the production of (super)hydrophobic coatings. In a second step, the influence of different plasma and UV induced functionalizations on the wetting characteristics of these materials is investigated. The experiments show that the superhydrophobic surfaces can be turned continuously and reversibly into hydrophilic (superhydrophilic) surfaces by means of the different treatment methods. The reversibility of these processes is studied in a third step. It is shown that the changes of the surface which are induced by the plasma treatment can be undone by means of EUV irradiation. The switchability of the surface due to external stimuli can be easily used for the controlled production of patterned surfaces. This is demonstrated by means of one simple example.
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81.65.-b Surface treatments
68.55.am Polymers and organics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Rx Nanocrystalline materials
68.08.Bc Wetting

High-temperature inert gas plasma magnetohydrodynamic energy conversion by using linear-shaped Faraday-type channel

Tomoyuki Murakami, Yunqin Zhuang, and Yoshihiro Okuno

J. Appl. Phys. 113, 063303 (2013); http://dx.doi.org/10.1063/1.4792056 (6 pages)

Online Publication Date: 14 February 2013

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We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact linear-shaped Faraday-type MHD electrical power generator is used. Short-time-duration single-pulse shock-tunnel-based experiments demonstrate the MHD energy conversion with varying total inflow temperature up to 9000 K and applied magnetic-flux density up to 4.0 T. The high-temperature plasma is transformed from the thermal-equilibrium state at the entrance to the weak-nonequilibrium state in the supersonic MHD channel. The discharge structure is reasonably homogeneous without suffering from serious streamer development. The power generation performance is monotonically improved by increasing total inflow temperature and strength of magnetic field. The enthalpy extraction efficiency of 13.1% and overall power density of 0.16 GW/m3 are attained. The local power density at the middle of the channel reaches 0.24 GW/m3.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Tc Shock waves and discontinuities
52.80.-s Electric discharges
52.25.Fi Transport properties
52.25.Kn Thermodynamics of plasmas

Linear stability of electron flow produced by field emission

A. Rokhlenko and J. L. Lebowitz

J. Appl. Phys. 113, 063304 (2013); http://dx.doi.org/10.1063/1.4792059 (8 pages)

Online Publication Date: 14 February 2013

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A linear stability analysis of the planar one dimensional space charge limited flow is performed when the current is determined by a current-field relation, e.g., the Fowler-Nordheim or any other emission model. The initial velocity is assumed the same for all emitted electrons. The flow is shown to be stable with decaying oscillations depending on the nature of the emission law, including in some situations non-oscillating slowly decaying modes. When the emission variations are due only to changes of the initial flow velocity, the time of decay can be much longer than the electron transit time for a given flow setup.
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79.70.+q Field emission, ionization, evaporation, and desorption
77.22.Jp Dielectric breakdown and space-charge effects
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