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Plasma Science, IEEE Transactions on

Issue 3 • Date June 2003

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Displaying Results 1 - 18 of 18
  • Very slowly decaying afterglow plasma in cryogenic helium gas

    Publication Year: 2003 , Page(s): 429 - 437
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (525 KB) |  | HTML iconHTML  

    A late afterglow period of cryogenic plasma with density less than 108 cm-3 in 4.2-K helium gas is measured, where the plasma is lost mainly through ambipolar diffusion. We fabricate a large stainless-steel cylindrical discharge vessel of 16.6 cm in diameter and 8.2 cm in length. The vessel is a TE011 mode cavity with resonant frequency 2.85 GHz and Q-value larger than 3000. The diffusion length of the cavity, 2.1 cm, is much larger than those previously reported on cryogenic plasmas. A high-voltage pulse of 15 kV, 600 A with duration 2.5 μ s is applied between tungsten needle electrodes to produce a plasma repeatedly. Gas pressure is varied from 0.08 to 1.1 torr. Temporal changes in plasma density and electron-atom momentum transfer collision frequency are measured by an improved method of microwave interferometer including the cavity. The plasma decay with time constant on the order of 1 s is observed. We can see very slowly fading fluorescent light with our naked eyes. The decay time is increased, if gas temperature is cooled below 4.2 K. View full abstract»

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  • Second-harmonic generation of a Gaussian laser beam in a self created magnetized plasma channel

    Publication Year: 2003 , Page(s): 324 - 328
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (385 KB) |  | HTML iconHTML  

    The second-harmonic generation of an intense self-guided right circularly polarized laser beam in a magnetized plasma is investigated. The laser imparts oscillatory velocity to electrons and exerts a radial ponderomotive force on them to create a depleted density channel. The critical power for self-focusing shows huge reduction as electron cyclotron frequency approaches the laser frequency (ωc → ω). In the presence of the self-created radial density gradient, the laser drives a density perturbation at the fundamental frequency. The density perturbation beats with the oscillatory velocity to produce a second harmonic current density, driving second harmonic radiation copropagating with the laser. The second harmonic, however, is azimuthally asymmetric with θ-variation as exp(iθ). Its amplitude shows resonant enhancement as ωc → ω. View full abstract»

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  • New method for detection of multipaction

    Publication Year: 2003 , Page(s): 396 - 404
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1083 KB) |  | HTML iconHTML  

    A new global method for unambiguous detection of multipaction in microwave communication systems is presented. Theory as well as experiments demonstrate the potential and usefulness of the method. A short review of existing methods for multipaction detection is given as a background, in order to illustrate the advantages of the new method. View full abstract»

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  • Electric probe measurements of high-voltage sheath collapse in cathodic arc plasmas due to surface charging of insulators

    Publication Year: 2003 , Page(s): 438 - 443
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    High-voltage sheath dynamics near a negatively biased substrate in cathodic arc plasmas are investigated using a biased electrical probe. Since the sheath is devoid of electrons, the sheath boundary can be inferred from the position where a positively biased probe draws no electron current. The extent of the sheath is primarily dependent on the plasma density, the ion velocity and the applied voltage. Using insulating substrates, the sheath boundary eventually retracts due to a dynamic reduction in the applied voltage. This reduction is caused by positive charge accumulation on the insulator surface. The collapse time of the sheath is dependent on the plasma density and the substrate characteristics. We believe this to be the first direct observation of the reduction in the width of the high-voltage sheath when implanting an electrical insulator using plasma-based ion implantation (PBII). This information is important when determining the optimal parameters for plasma-based ion implantation of insulators. Our measurements are compared with theoretical predictions based on the Child-Langmuir equations for high-voltage sheaths. By choosing appropriate values for the secondary electron coefficient the theory could be made to fit the experimental data. A discussion of the validity of the choice of secondary electron coefficients is presented. View full abstract»

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  • Characteristics of charged and metastable species in micro-discharges of AC- plasma display panel

    Publication Year: 2003 , Page(s): 329 - 332
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB)  

    The temporal effects of charged and metastable particles in the micro-discharges of an AC plasma display panel (AC-PDP) were investigated under actual driving conditions. The discharge gas used in the 4-in PDP was Neon + 4% Xenon. The discharge characteristics in terms of the time scale related to the space-charge decay, wall charge decay, metastable decay, and charge accumulation were investigated using a pulse technique. For Neon + 4% Xenon gas-mixture discharges of 500 torr, 4 μs was related to the time scale of the space-charge decay and wall-charge accumulation time. The minimum sustain voltage started to dramatically increase at 20 μs, which was related to the time scale of the metastable particles. Whereas, after 40 μs, the minimum sustain voltage slowly increased with a slope of 0.01581, which was related to the inverse of the time scale of the wall charge decay. View full abstract»

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  • Triggering and guiding of an upward positive leader from a ground rod with an ultrashort laser pulse. I. Experimental results

    Publication Year: 2003 , Page(s): 377 - 386
    Cited by:  Papers (11)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (598 KB) |  | HTML iconHTML  

    Using a plasma channel produced by an ultrashort laser pulse, we have studied the laser triggering and guiding of a positive leader from the tip of a 2-m vertical rod standing on the bottom plane of a 7-m plane-plane gap. The purpose of this setup was to reproduce in the laboratory the electric field conditions leading to the onset of a positive upward leader from a ground rod as a downward negative leader is approaching during a thunderstorm, in order to demonstrate the working principle of a possible future laser lightning rod. The leader triggering properties of the laser-created plasma channel have been studied as a function of the synchronization of the laser pulse with the voltage impulse applied to the gap. We show that the laser pulse reduces the inception voltage of the leader compared to its normal value and that the laser plasma channel guides the propagation of the upward leader at a velocity ten times higher than that of an ordinary leader, with a significantly lower charge per unit length. We show that laser guiding of the leader significantly reduces the breakdown voltage of the gap and that the effect of the laser channel at the end of a lightning rod can be compared quite favorably with the effect of an additional metal rod of the same length. View full abstract»

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  • Doppler spectroscopy of hydrogen and deuterium Balmer alpha line in an abnormal glow discharge

    Publication Year: 2003 , Page(s): 444 - 454
    Cited by:  Papers (27)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB) |  | HTML iconHTML  

    The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative explanation of line wings intensity dependence is related to the sputtering of cathode material and back-scattering coefficients of incident hydrogen or deuterium ions and atoms from cathode surface. The influence of the light reflected on a cathode surface to the line shape measurements along discharge axis is considered. In hydrogen, deuterium, and Ar+3%H2 discharges, basic mechanisms of fast hydrogen generation and excitation are studied. The shape and intensities of the Hα line profiles in pure hydrogen and in argon-hydrogen mixture may be correlated with hydrogen atom-carrier gas collision excitation cross sections. In order to assess the importance of reflected fast hydrogen atoms back scattered from the cathode surface, for the Balmer line shape formation, a simulation program is used. The results are in a qualitative agreement with Balmer line shapes observations. View full abstract»

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  • Circuit model for two-electrode AC discharge

    Publication Year: 2003 , Page(s): 362 - 368
    Cited by:  Papers (4)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (501 KB) |  | HTML iconHTML  

    This paper presents a circuit model for a two-electrode AC discharge, which has two electrodes separated from the discharge gap by an insulator. The model consists of a series connection of an equivalent circuit for plasma and two capacitors for insulator. The equivalent circuit for plasma was constructed using the measured electrical properties of a two-electrode DC discharge. The validity of model was checked with experiments on a three-electrode test device; two electrodes exposed to the discharge gap and the other electrode separated from the discharge gap by an insulator. The measured voltages of the test device are compared with those obtained by circuit simulation. For various waveforms, which are being used widely to drive an AC plasma display panel, the results of circuit simulation agree well with experiment. View full abstract»

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  • Interaction of electromagnetic waves with a magnetized nonuniform plasma slab

    Publication Year: 2003 , Page(s): 405 - 410
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB) |  | HTML iconHTML  

    The absorption, reflection, and transmission of electromagnetic waves by a nonuniform plasma slab immersed in an ambient uniform magnetic field of various strengths are studied in this paper. The effects of the plasma parameters and magnetic field strength on the absorbed, reflected, and transmitted power are discussed. The magnetized nonuniform plasma slab is modeled by a series of magnetized uniform plasma subslabs. The calculation results show that the effects of the magnetic field strength and density gradient on the absorbed power, as well as the frequency band of resonant absorption, are significant. A complete analysis utilizing the scattering matrix method is also used to compare the above calculation results which neglect multiple reflections between subslab interfaces. Broadband absorption of electromagnetic waves can be achieved by changing the magnetic field strength and plasma density. More than 90% of the electromagnetic wave power can be absorbed in a magnetized nonuniform plasma slab with width of 12 cm and the absorption bandwidth can range from 1 to 20 GHz with different plasma parameters and external magnetic field strengths. View full abstract»

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  • Comparison of excessive Balmer α line broadening of inductively and capacitively coupled RF, microwave, and glow-discharge hydrogen plasmas with certain catalysts

    Publication Year: 2003 , Page(s): 338 - 355
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (780 KB)  

    From the width of the 656.3-nm Balmer α line emitted from inductively and capacitively coupled radio frequency (RF), microwave, and glow-discharge plasmas, it was found that inductively coupled RF helium-hydrogen and argon-hydrogen plasmas showed extraordinary broadening corresponding to an average hydrogen atom energy of 250-310 and 180-230 eV, respectively, compared to 30-40 and 50-60 eV, respectively, for the corresponding capacitively coupled plasmas. Microwave helium-hydrogen and argon-hydrogen plasmas showed significant broadening corresponding to an average hydrogen atom energy of 180-210 and 110-130 eV, respectively. The corresponding results from the glow-discharge plasmas were 33-38 and 30-35 eV, respectively, compared to ≈ 4 eV for plasmas of pure hydrogen, neon-hydrogen, and xenon-hydrogen maintained in any of the sources. Similarly, the average electron temperatures Te for helium-hydrogen and argon-hydrogen inductively coupled RF and microwave plasmas were high (43 200 ± 5% K, 18 600 ± 5% K, 30 500 ± 5% K, and 13 700 ± 5% K, respectively); compared to 9300 ± 5% K, 7300 ± 5% K, 8000 ± 5% K, and 6700 ± 5% K for the corresponding plasmas of xenon-hydrogen and hydrogen alone, respectively. Stark broadening or acceleration of charged species due to high electric fields cannot explain the inductively coupled RF and microwave results since the electron density was low and no high field was present. Rather, a resonant energy transfer mechanism is proposed. View full abstract»

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  • Faraday dosimetry characteristics of PIII doping processes

    Publication Year: 2003 , Page(s): 369 - 376
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB) |  | HTML iconHTML  

    A Faraday cup dosimetry system was developed and characterized to address the issues of plasma immersion ion implantation (PIII) dose measurements. Pure ion current was measured by using an electrostatic suppression mechanism combined with high-bandwidth fiber-optic electronics to isolate high-voltage pulses and eliminate the primary and secondary electron and displacement currents. The ion-current waveform measured by the Faraday cup was verified by an XPDP1 particle-in-cell simulation. All of the positively charged ions striking the target surface were counted for implant dose by the Faraday cup so that both high-energy implant dose during the pulse and low-energy implant dose between pulses can be separately determined. The dose of the high-energy implant during pulses, which is more influential on the junction depth, can be measured with a fairly good accuracy, although the low-energy implant dose cannot be accurately measured due to more complicated surface effects. Compared with other dosimetry methods for PIII doping processes, the Faraday dosimetry technique offers better repeatability and controllability for PIII processes due to its direct, in-situ manner. View full abstract»

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  • Modeling refraction characteristics of silicon nitride film deposited in a SiH4-NH3-N2 plasma using neural network

    Publication Year: 2003 , Page(s): 317 - 323
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (627 KB) |  | HTML iconHTML  

    Silicon nitride has been deposited using plasma-enhanced chemical deposition (PECVD) equipment. The PECVD process was characterized by conducting a 26-1 fractional factorial experiment on six experimental factors, including substrate temperature, pressure, radio frequency (RF) power, ammonia NH3, silane SiH4, and nitrogen N2 flow rates. Refractive characteristics of the deposited film were examined by modeling the refractive index as a function of experimental factors. A helium-neon laser with a wavelength 6328 Å was used to measure the refractive index. To evaluate the appropriateness of the model, the network trained with 32 experiments was then tested with 12 experiments not pertaining to the training data. Several learning factors involved in training neural networks were optimized and an accurate prediction model with the root mean-squared error of 0.018 was achieved. Compared to statistical regression model, the neural network model demonstrated an improvement of more than 65%. Using various three-dimensional plots, underlying deposition mechanisms were qualitatively estimated. For the limited experimental ranges, the index increased with increasing SiH4 flow rate. With an increase in either NH3 or N2, meanwhile, the index decreased consistently. The index also increased with increasing substrate temperature or pressure. The effects of the temperature were very complex as it interacted with other factors. View full abstract»

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  • Triggering and guiding of an upward positive leader from a ground rod with an ultrashort laser pulse. II. Modeling

    Publication Year: 2003 , Page(s): 387 - 395
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (362 KB) |  | HTML iconHTML  

    We have used the Bondio-Gallimberti model of positive leader propagation to simulate laboratory experiments of laser triggering and guiding of upward leaders initiated from a ground rod. The model proves to be capable of reproducing all the important features of laser-guided leader propagation that have been observed experimentally. The leader guiding effect of the laser-created plasma channel is taken into account in the model by adjusting the value of the charge per unit length of the leader, which has been measured in the laboratory to be lower for a laser-guided leader than for an ordinary one. The charge per unit length of the leader is related in the model to the critical temperature at which the air in the transition region at the leader tip must be heated to be conductive enough to become a new leader portion. For an ordinary leader, this critical temperature is 1500 K, at which the electrons all detach from the negative ions in the leader corona, increasing the air conductivity. We give the interpretation that in the case of the laser-guided leaders, because of the relatively high density of negative ions per unit length in the laser-ionized channel, the right conditions of conductivity can be met in the transition region without the electrons being all detached from the ions, allowing a reduction of the critical temperature and of the charge per unit length. View full abstract»

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  • Control of implantation area in direct-current plasma immersion ion implantation (DC-PIII)

    Publication Year: 2003 , Page(s): 356 - 361
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    In plasma immersion ion implantation (PIII) of planar samples such as silicon wafers in the PIII-ion-cut as well as separation by plasma implantation of oxygen (SPIMOX) processes, the only important ions are the ones arriving at the top surface. Ions implanted into the other surfaces are, in fact, undesirable as they reduce the efficiency of the power supply and plasma source and give rise to metallic contamination. We have demonstrated direct-current PIII (DC-PIII) by using a grounded grid to separate the vacuum chamber for planar sample implantation. The advantages include lower equipment cost, higher power and time efficiency, larger impact energy, and last but not least, smaller instrument footprint. In this paper, we investigate the control of the implantation area by adjusting the radius of the extraction hole, the distance between the conducting grid and the sample, and the radius of the wafer stage. Theoretical simulation is conducted using particle-in-cell and experiments are also carried out. Our results indicate that the implanted area increases with the radius of the extraction hole and wafer stage, but decreases with a larger distance between the grid and sample. The effects of the extraction hole radius Gr are the largest, followed by the placement of the sample to the conducting grid H. The wafer stage poses the least influence in this respect, but a proper wafer stage dimension improves the lateral implant dose and incident angle homogeneity. Our simulation and experimental results suggest optimal ratios of these parameters for each wafer size. View full abstract»

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  • Diagnostics of dielectric barrier discharges in noble gases: atmospheric pressure glow and pseudoglow discharges and spatio-temporal patterns

    Publication Year: 2003 , Page(s): 411 - 421
    Cited by:  Papers (63)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2444 KB) |  | HTML iconHTML  

    We present experimental results of atmospheric pressure glow discharges (APGD) in a dielectric barrier discharge reactor. These are examined in different noble gases and in the N2/O2 system (air and pure N2), under varying experimental conditions (frequency f; gap length d; and electric field intensity E). Discharge diagnostics have been carried out using ultrahigh speed imaging, and synchronous dual-detection of light emission and current-voltage measurements, the former using a photomultiplier . The time evolutions of the discharges and of columnar patterns in regular geometric arrangements at atmospheric pressure under different experimental conditions are reported for all of the noble gases studied here. We present evidence that columnar patterns and APGD are manifestations of the same discharge physics, which is discussed with reference to recent work reported by others. View full abstract»

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  • Industrial-scale experiments of desulfuration of coal flue gas using a pulsed corona discharge plasma

    Publication Year: 2003 , Page(s): 333 - 337
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (246 KB) |  | HTML iconHTML  

    The flow rate of flue gas in the industrial experiments was 3000 Nm3/h. The flue gas from the boiler burning coal was used. The influences of operating parameters on the efficiency of desulfuration (DeSO2) were studied, which include the retention period of flue gas in the reactor, the initial concentration of SO2 in flue gas, a mole ratio of NH3 to SO2 in the gas, the temperature of the gas, as well as the power consumption of pulsed corona discharges. The experimental results shown that the efficiency of DeSO2 was above 80%, when the initial concentration of SO2 was 1000 ∼ 2000 ppm, the gas temperature was 60 °C ∼ 75 °C, the retention period was more than 5.8 s, a mole ratio of NH3 to SO2 was 2 : 1, the water content in flue gas was above 6%, and he consumption was 2.5 ∼ 3.5 Wh/Nm3. View full abstract»

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  • Large-gap AC coplanar plasma display cells: macro-cell experiments and 3-D simulations

    Publication Year: 2003 , Page(s): 422 - 428
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB) |  | HTML iconHTML  

    We present experimental and simulation studies of the plasma in a macroscopic AC plasma display panel discharge cell operating with a large coplanar gap. We find that the xenon excitation efficiency is much larger than that in the conventional, small-gap electrode configuration but with larger sustaining voltage. We discuss the discharge mode and efficiency in such large gap configurations, with the help of time resolved optical diagnostics and simulations. View full abstract»

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  • Temperatures and charged particle densities in a metal-halide arc lamp; comparison of nonequilibrium spectroscopy and thermochemical calculations

    Publication Year: 2003 , Page(s): 310 - 316
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (414 KB) |  | HTML iconHTML  

    Mass and energy spatial flows within high-pressure lighting plasmas containing metal halides may affect the plasma state of equilibrium. In this study, the effect of the thermochemical equilibrium assumptions on the determination of the plasma parameters in a sodium-iodide arc lamp is experimentally investigated. The electron temperature and electron, mercury-ion, and sodium-ion density as a function of the radial distance from the arc axis in a sodium-iodide arc lamp are determined using an emission spectroscopy technique, which is free of equilibrium assumptions. Comparison of the results with those assuming thermochemical equilibrium shows that the actual plasma state differs from that at equilibrium. Possible factors causing the observed differences are discussed. View full abstract»

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Aims & Scope

IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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Editor-in-Chief
Steven J. Gitomer, Ph.D.
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Guest Scientist, Los Alamos National Laboratory
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