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Title: Radiation Efficiency of AC-excited Micro Hollow Cathode Discharges

Abstract

This contribution reports on micro hollow cathode discharges (MHCD) generated in a device supplied by rectified but non-filtered low-frequency currents to preserve the cathode function of one micro electrode. The vacuum ultraviolet (VUV) radiation efficiency of such an MHCD was investigated in high-pressure argon in the frequency range from 40 kHz to 140 kHz. Both the currents and voltages of the MHCD device are nonlinear and the power input shows a flat maximum at about 50 kHz. The VUV relative efficiency also displays a more pronounced maximum at this frequency but remains still comparable with those of the dc supplied MHCD. Unfortunately, this VUV efficiency rather refers to the resonant lines of oxygen impurity at about 130.5 nm and not to the argon excimer radiation.

Authors:
; ;  [1]; ;  [2]
  1. Al.I.Cuza-University of Iasi, Dept. Plasma Phys., Blvd. Carol I, No. 11, R-700506 Iasi (Romania)
  2. F.A.-University of Erlangen-Nueremberg, Phys. Dept. I, Erwin-Rommel-Str., No.1, D-91058 Erlangen (Germany)
Publication Date:
OSTI Identifier:
20797929
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 812; Journal Issue: 1; Conference: PLASMA 2005: International conference on research and applications of plasmas; 3. German-Polish conference on plasma diagnostics for fusion and applications; 5. French-Polish seminar on thermal plasma in space and laboratory, Opole-Turawa (Poland), 6-9 Sep 2005; Other Information: DOI: 10.1063/1.2168854; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; EFFICIENCY; ELECTRIC CURRENTS; ELECTRIC POTENTIAL; FAR ULTRAVIOLET RADIATION; GLOW DISCHARGES; HOLLOW CATHODES; KHZ RANGE; LIGHT SOURCES; NONLINEAR PROBLEMS; OXYGEN; PLASMA DIAGNOSTICS; PLASMA IMPURITIES

Citation Formats

Biborosch, L. D., Popescu, S., Luca, D., Petzenhauser, I., and Frank, K. Radiation Efficiency of AC-excited Micro Hollow Cathode Discharges. United States: N. p., 2006. Web. doi:10.1063/1.2168854.
Biborosch, L. D., Popescu, S., Luca, D., Petzenhauser, I., & Frank, K. Radiation Efficiency of AC-excited Micro Hollow Cathode Discharges. United States. doi:10.1063/1.2168854.
Biborosch, L. D., Popescu, S., Luca, D., Petzenhauser, I., and Frank, K. Sun . "Radiation Efficiency of AC-excited Micro Hollow Cathode Discharges". United States. doi:10.1063/1.2168854.
@article{osti_20797929,
title = {Radiation Efficiency of AC-excited Micro Hollow Cathode Discharges},
author = {Biborosch, L. D. and Popescu, S. and Luca, D. and Petzenhauser, I. and Frank, K.},
abstractNote = {This contribution reports on micro hollow cathode discharges (MHCD) generated in a device supplied by rectified but non-filtered low-frequency currents to preserve the cathode function of one micro electrode. The vacuum ultraviolet (VUV) radiation efficiency of such an MHCD was investigated in high-pressure argon in the frequency range from 40 kHz to 140 kHz. Both the currents and voltages of the MHCD device are nonlinear and the power input shows a flat maximum at about 50 kHz. The VUV relative efficiency also displays a more pronounced maximum at this frequency but remains still comparable with those of the dc supplied MHCD. Unfortunately, this VUV efficiency rather refers to the resonant lines of oxygen impurity at about 130.5 nm and not to the argon excimer radiation.},
doi = {10.1063/1.2168854},
journal = {AIP Conference Proceedings},
number = 1,
volume = 812,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • A global (volume-averaged) model of the self-pulsing regime of micro-hollow cathode discharges working in argon gas is proposed. The power balance is done using an equivalent circuit model of the discharge that allows the current and voltage dynamics to be calculated. The fraction of the total power dissipated in the discharge that contributes to electron heating is deduced from a sheath model previously described. The particle balance is first done in a very simplified reaction scheme involving only electrons, argon atomic ions, and argon molecular ions. In a second step, the excited states (the metastable state Ar*({sup 3}P{sub 2}) andmore » the resonant state Ar*({sup 3}P{sub 1})) are included in the particle balance equations. The models are compared to experiments and several conclusions are drawn. The model without excited states underestimates the electron density and does not capture well the trends in pressure. The model with the excited states is in better agreement which shows that multi-step ionization plays a significant role. The time-evolution of the electron density follows closely that of the discharge current but the excited states density presents two peaks: (i) the first at the early stage of the current peak due to direct excitation with high electron temperature, (ii) the second at the end of the current (and electron density) peak due to large production of excited states by electron-ion recombination at very low electron temperature.« less
  • Micro hollow cathode discharges (MHCD) were produced using 250 μm thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 μm thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the measurement of He*({sup 3}S{sub 1}) metastable atomsmore » density by tunable diode laser spectroscopy. At the ignition of the microdischarges, 2 μs long current peak as high as 24 mA was observed, sometimes followed by low amplitude damped oscillations. At helium pressure above 400 Torr, an oscillatory behaviour of the discharge current was observed just before the extinction of the microdischarges. The same type of instability in the extinction period at high pressure also appeared on the density of He*({sup 3}S{sub 1}) metastable atoms, but delayed by a few μs relative to the current oscillations. Metastable atoms thus cannot be at the origin of the generation of the observed instabilities.« less
  • A novel, nonequilibrium, high-pressure, direct current discharge, the microhollow cathode discharge, has been found to be an intense source of xenon and argon excimer radiation peaking at wavelengths of 170 and 130 nm, respectively. In argon discharges with a 100 {mu}m diam hollow cathode, the intensity of the excimer radiation increased by a factor of 5 over the pressure range from 100 to 800 mbar. In xenon discharges, the intensity at 170 nm increased by two orders of magnitude when the pressure was raised from 250 mbar to 1 bar. Sustaining voltages were 200 V for argon and 400 Vmore » for xenon discharges, at current levels on the order of mA. The resistive current{endash}voltage characteristics of the microdischarges indicate the possibility to form arrays for direct current, flat panel excimer lamps. {copyright} {ital 1998 American Institute of Physics.}« less
  • By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 {mu}m, we were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure. High-pressure discharges in xenon were found to be strong sources of excimer radiation. Highest intensities at a wavelength of 172 nm were obtained at a pressure of 400 Torr. At this pressure, the vacuum ultraviolet (VUV) radiant power of a single discharge operating at a forward voltage of 220 V and currents exceeding 2 mA reaches values between 6{percent}more » and 9{percent} of the input electrical power. The possibility to form arrays of these discharges allows the generation of flat panel VUV lamps with radiant emittances exceeding 50 W/cm{sup 2}. {copyright} {ital 1998 American Institute of Physics.}« less
  • A detailed experimental study of space charge formation and ionization growth in Transient Hollow Cathode Discharges (THCD) is presented. The experiment was performed with an applied step voltage up to 30 kV, with rise time less than 50 ns. The discharge was operated in different gases, at pressures in the range 50--750 mTorr, with cathode apertures ranging from 1 to 5 mm diameter and 5 to 20 mm long, with 10 cm electrode separation. Spatial charge formation, both in the Hollow Cathode Region (HCR) and inter electrode space, has been studied with a capacitive probe array. Properties of high energymore » electron beams have been measured with a beam-target scintillator-photomultiplier arrangement. Detailed correlations of the electron beam evolution with the charge probe signals inside and outside the HCR clearly demonstrate the role of the electron beam in the initial formation and late evolution of a virtual anode and, in turn, the field enhanced ionization when the anode potential is brought close to the HCR. Theses results clearly identify the different regimes in which the Hollow Cathode plays a significant role in ionization growth in the inter electrode space and in the processes which eventually lead to electric breakdown.« less