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1 Apr 2012

Volume 111, Issue 7, Articles (07xxxx)

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J. Appl. Phys. 111, 071101 (2012); http://dx.doi.org/10.1063/1.3694674 (23 pages)

Shunfeng Li and Andreas Waag
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back to top Plasmas and Electrical Discharges

Photonic band structures of two-dimensional magnetized plasma photonic crystals

L. Qi

J. Appl. Phys. 111, 073301 (2012); http://dx.doi.org/10.1063/1.3699213 (8 pages) | Cited 3 times

Online Publication Date: 4 April 2012

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By using modified plane wave method, photonic band structures of the transverse electric polarization for two types of two-dimensional magnetized plasma photonic crystals are obtained, and influences of the external magnetic field, plasma density, and dielectric materials on the dispersion curves are studied, respectively. Results show that two areas of flat bands appear in the dispersion curves due to the role of external magnetic field, and the higher frequencies of the up and down flat bands are corresponding to the right-circled and left-circled cutoff frequencies, respectively. Adjusting external magnetic field and plasma density can not only control positions of the flat bands, but also can control the location and width of the local gap; increasing relative dielectric constant of the dielectric materials makes omni-direction gaps appear.
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42.70.Qs Photonic bandgap materials
52.25.-b Plasma properties
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Optical breakdown threshold investigation of 1064 nm laser induced air plasmas

Magesh Thiyagarajan and Shane Thompson

J. Appl. Phys. 111, 073302 (2012); http://dx.doi.org/10.1063/1.3699368 (8 pages)

Online Publication Date: 6 April 2012

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We present the theoretical and experimental measurements and analysis of the optical breakdown threshold for dry air by 1064 nm infrared laser radiation and the significance of the multiphoton and collisional cascade ionization process on the breakdown threshold measurements over pressures range from 10 to 2000 Torr. Theoretical estimates of the breakdown threshold laser intensities and electric fields are obtained using two distinct theories namely multiphoton and collisional cascade ionization theories. The theoretical estimates are validated by experimental measurements and analysis of laser induced breakdown processes in dry air at a wavelength of 1064 nm by focusing 450 mJ max, 6 ns, 75 MW max high-power 1064 nm IR laser radiation onto a 20 μm radius spot size that produces laser intensities up to 3 – 6 TW/cm2, sufficient for air ionization over the pressures of interest ranging from 10 to 2000 Torr. Analysis of the measured breakdown threshold laser intensities and electric fields are carried out in relation with classical and quantum theoretical ionization processes, operating pressures. Comparative analysis of the laser air breakdown results at 1064 nm with corresponding results of a shorter laser wavelength (193 nm) [M. Thiyagarajan and J. E. Scharer, IEEE Trans. Plasma Sci. 36, 2512 (2008)] and a longer microwave wavelength (108 nm) [A. D. MacDonald, Microwave Breakdown in Gases (Wiley, New York, 1966)]. A universal scaling analysis of the breakdown threshold measurements provided a direct comparison of breakdown threshold values over a wide range of frequencies ranging from microwave to ultraviolet frequencies. Comparison of 1064 nm laser induced effective field intensities for air breakdown measurements with data calculated based on the collisional cascade and multiphoton breakdown theories is used successfully to determine the scaled collisional microwave portion. The measured breakdown threshold of 1064 nm laser intensities are then scaled to classical microwave breakdown theory after correcting for the multiphoton ionization process for different pressures and good agreement, regarding both pressure dependence and breakdown threshold electric fields, is obtained. The effect of the presence of submicron particles on the 1064 nm breakdown threshold was also investigated. The measurements show that higher breakdown field is required, especially at lower pressures, and in close agreement with classical microwave breakdown theory and measurements in air.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.70.Gw Radio-frequency and microwave measurements
52.80.Pi High-frequency and RF discharges
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Jm Ionization of plasmas

Multiple scattering of ultra-high frequency electromagnetic waves by two plasma cylinders

Wu Xiao-po, Shi Jia-ming, Wang Jia-chun, Yuan Zhong-cai, Xu Bo, Zhao Da-peng, Chen Zong-sheng, and Lin Zhi-dan

J. Appl. Phys. 111, 073303 (2012); http://dx.doi.org/10.1063/1.3702406 (6 pages)

Online Publication Date: 9 April 2012

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Multiple scattering of ultrahigh frequency (UHF) electromagnetic waves by two argon plasma cylinders is investigated, rigorously applying the boundary value method. The results are verified and validated with the method of moments. Approximate expressions for the far field, taking into account the interaction between the plasma cylinders, are derived briefly after some mathematical manipulations. Numerical results are presented for the case of E-polarized UHF incidence with varied striking angles and different separation distances between the cylinders; comparisons of the scattering distributions are given in detail as well. It is found that the interaction between the plasma cylinders plays a non-negligible role in scattered energy redistributing, which is useful in the future research of intelligent plasma antennas.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
02.60.-x Numerical approximation and analysis

Atmospheric pressure dielectric barrier microplasmas inside hollow-core optical fibers

Longfei Ji, Dongping Liu, Ying Song, and Jinhai Niu

J. Appl. Phys. 111, 073304 (2012); http://dx.doi.org/10.1063/1.3702818 (6 pages) | Cited 3 times

Online Publication Date: 12 April 2012

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An atmospheric glow microplasma is generated in the hollow core of microns-thick optical fibers (>1 m long) when the sinusoidal voltage with a peak voltage of 5 kV and a frequency of 5.0 kHz is applied to these microelectrodes along the outside of optical fibers. Measurements show that the atmospheric glow microdischarge consists of current pulses with amplitudes of tens of amperes and pulse widths of several microseconds. Atmospheric surface barrier discharges are formed along the inner surface of hollow optical fibers between adjacent microelectrodes, which results in the pulsed glow microdischarges. By flowing octafluorocyclobutane (c-C4F8)/helium (He) mixtures through the hollow-core optical fiber, fluorocarbon polymer (FCP) coatings are deposited on the inner surface of the > 1 m long optical fiber. Analysis indicates that the glow microdischarge contributes to the uniform deposition of FCP coatings on the inner surface of hollow fibers. The in situ optical emission measurements show that various carbon-containing species, such as CF2, CN, and C2 are generated in the visually uniform microplasmas. The discharge mechanism is discussed based on the I-V and optical emission measurements and FCP coating characterizations.
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42.79.-e Optical elements, devices, and systems
42.81.-i Fiber optics

Stability of very-high pressure arc discharges against perturbations of the electron temperature

M. S. Benilov and U. Hechtfischer

J. Appl. Phys. 111, 073305 (2012); http://dx.doi.org/10.1063/1.3702469 (8 pages) | Cited 1 time

Online Publication Date: 13 April 2012

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See Also: Publisher's Note

Show Abstract
We study the stability of the energy balance of the electron gas in very high–pressure plasmas against longitudinal perturbations, using a local dispersion analysis. After deriving a dispersion equation, we apply the model to a very high–pressure (100 bar) xenon plasma and find instability for electron temperatures, Te, in a window between 2400 K and 5500-7000 K, depending on the current density (106–108 A/m2). The instability can be traced back to the Joule heating of the electron gas being a growing function of Te, which is due to a rising dependence of the electron-atom collision frequency on Te. We then analyze the Te range occurring in very high–pressure xenon lamps and conclude that only the near-anode region exhibits Te sufficiently low for this instability to occur. Indeed, previous experiments have revealed that such lamps develop, under certain conditions, voltage oscillations accompanied by electromagnetic interference, and this instability has been pinned down to the plasma-anode interaction. A relation between the mechanisms of the considered instability and multiple anodic attachments of high-pressure arcs is discussed.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Fi Transport properties
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
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