Навчально-науковий інститут "Фізико-технічний факультет"
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Документ Experimental Study of a Low-Pressure Glow Discharge in Air in Large-Diameter Discharge Tubes: I. Conditions for the Normal Regime of a Glow Discharge(Plasma Physics Reports, 2000-12) Lisovskiy, V.; Yakovin, S.The initiation and characteristics of a low-pressure glow discharge in air in large-diameter discharge tubes are studied. A deviation from the Paschen law is observed: the breakdown curves Udc(pL) shift toward the higher values of Udc and pL as the interelectrode distance L increases. It is shown that the normal regime of a glow discharge is accompanied by gas ionization in the anode sheath. This takes place only for pL values lying to the right of the inflection point in the breakdown curve. The cathode-sheath characteristics in the normal and abnormal regimes of an air discharge for a duralumin cathode are determined. The axial profiles of the ion density, electron temperature, and plasma potential, as well as the anode voltage drop, are measured at various air pressures.Документ Scaling Law for a Low-Pressure Gas Breakdown in a Homogeneous DC Electric Field(Journal of Experimental and Theoretical Physics Letters, 2000-02) Lisovskiy, V.; Yakovin, S.Gas breakdown in nitrogen, air, and oxygen in a dc electric field at various interelectrode distances L is studied experimentally. A scaling law for a low-pressure gas breakdown Udc=f(pL,L/R) is deduced. According to this scaling law, the breakdown voltage Udc is a function not only of the product of the gas pressure p and the gap length L, but also of the ratio of the gap length L to the chamber radius R. It is shown that, for any dimensions of the cylindrical discharge chamber (in the range of L/R under investigation), the ratio of the breakdown electric field to the gas pressure p at the minimum of the ignition curve remains constant: (Edc/p)min = const. A method for calculating the ignition curve in a cylindrical discharge chamber with arbitrary values of L and R is proposed.Документ Low-pressure gas breakdown in uniform dc electric field(JOURNAL OF PHYSICS D: APPLIED PHYSICS, 2000-11) Lisovskiy, V.; Yakovin, S.; Yegorenkov, V.This paper studies in experiment and theory the breakdown of argon, nitrogen, air and oxygen in a uniform dc electric field at different discharge gaps L, discharge tube radii R and cathode materials. At arbitrary geometric dimensions of the cylindrical discharge vessel and cathode materials the ratio of the breakdown electric field value to the gas pressure p at the minimum of the breakdown curves is shown to remain constant, (Edc/p)min ≈ constant. A modified breakdown law for the low-pressure dc discharge Udc = f (pL, L/R) is obtained. That is, the breakdown voltage Udc is shown to depend not only on the product pL, but also on the ratio L/R. A method is presented enabling one to predict a dc breakdown curve in the cylindrical discharge vessel possessing arbitrary L and R values from the measured data on the dc breakdown.Документ Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen(www.elsevier.com/locate/vacuum, 2004-01) Lisovskiy, V.; Yegorenkov, V.We report the recorded current–voltage characteristics of a RF capacitive discharge in oxygen. Low-frequency oscillations of the plasma potential in a kilohertz frequency range are observed to accompany the transition of the discharge from a weak- (a-) to a strong-current (g-) regime in the low-pressure range. The weak-current regime of the RF capacitive discharge is observed within the pressure range limited not only from the medium pressure side but also from the lower-pressure one. Electron temperature and plasma density are registered with a probe technique.Документ The effect of discharge chamber geometry on the ignition of low-pressure rf capacitive discharges(PHYSICS OF PLASMAS, 2005-09) Lisovskiy, V.; Martins, S.; Landry, K.; Douai, D.; Booth, Jean-Paul; Cassagne, V.; Yegorenkov, V.This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder (“symmetric parallel plate”), parallel plates surrounded by a grounded metallic cylinder (“asymmetric parallel plate”), and parallel plates inside a much larger grounded metallic chamber (“large chamber”). The breakdown curves for the symmetric chamber have a multivalued section at low pressure. For the asymmetric chamber the breakdown curves are shifted to lower pressures and rf voltages, but the multivalued feature is still present. At higher pressures the breakdown voltages are much lower than for the symmetric geometry. For the large chamber geometry the multivalued behavior is not observed. The breakdown curves were also calculated using a numerical model based on fluid equations, giving results that are in satisfactory agreement with the measurements.Документ Double layer onset inside the near-electrode sheath of a RF capacitive discharge in oxygen(www.elsevier.com/locate/vacuum, 2006-04) Lisovskiy, V.; Yegorenkov, V.This paper reports the axial profiles of the electron temperature Te in the RF capacitive discharge in oxygen recorded with a probe technique. We observed the Te peaks near the boundaries of the sheaths as well as inside the near-electrode sheath. The Te peak inside the sheath is, probably, due to the formation of the double layer at the anode phase of this near-electrode sheath. The assumption of a double layer formation is also supported by the photos of the sheath glow making evident the bright region inside the sheath. The results of our measurements agree with our fluid simulation satisfactorily.Документ Electron drift velocity in argon, nitrogen, hydrogen, oxygen and ammonia in strong electric fields determined from rf breakdown curves(JOURNAL OF PHYSICS D: APPLIED PHYSICS, 2006-02) Lisovskiy, V.; Booth, Jean-Paul; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.We report measurements of the breakdown curves for low-pressure rf capacitive discharges in nitrogen, hydrogen, argon, oxygen and ammonia. The electron drift velocity in these gases was deduced, as a function of reduced electric field, from the low-pressure turning points of the breakdown curves. The equation for rf breakdown proposed by Kihara (1952 Rev. Mod. Phys. 24 52) allows the position of both the turning point and the breakdown curve minimum to be calculated from the transport properties of each gas. Therefore we propose a new technique to determine the electron drift velocity from the position of the rf breakdown curve minima. We have determined the drift velocity in the range E/p = 52–1324 Vcm−1 Torr−1 for nitrogen, E/p = 33–720 Vcm−1 Torr−1 for argon, E/p = 32–713 Vcm−1 Torr−1 for ammonia, E/p = 32–550 Vcm−1 Torr−1 for hydrogen and E/p = 69–1673 Vcm−1 Torr−1 for oxygen.Документ Electron drift velocity in N2O in strong electric fields determined from rf breakdown curves(JOURNAL OF PHYSICS D: APPLIED PHYSICS, 2006-04) Lisovskiy, V.; Booth, Jean-Paul; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.We report measurements of the breakdown curves of an rf capacitive discharge in low pressure nitrous oxide. The electron drift velocity was determined from the locations of the turning point and of the minimum in the breakdown curves in the range E/p = 87–840 Vcm−1 Torr−1. We compare our results with values calculated from the published cross-sections in the range E/p = 1–5000 Vcm−1 Torr−1 and find good agreement.Документ A technique for evaluating the RF voltage across the electrodes of a capacitively-coupled plasma reactor(http://www.edpsciences.org/epjap, 2006-10) Lisovskiy, V.; Booth, Jean-Paul; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.We propose a new technique for evaluating the RF voltage across the electrodes of low-pressure capacitively-coupled plasma reactors when direct measurements are not possible. It is based on determining the coordinates of the turning point in the RF breakdown curve and using known values of the electron drift velocity for the gas. The results are in good agreement with those obtained by direct measurements at the driven electrode. Furthermore it allows RF breakdown curves to be determined for different frequencies, giving results that are physically reasonable (coincidence of right-hand branches) and in agreement with other published results. The technique for determining RF voltage we proposed is valid when there is no discharge plasma between electrodes (e.g., before gas breakdown), as well as for negligibly small discharge currents (before extinction of the weak-current discharge mode).Документ Modes and the alpha-gamma transition in rf capacitive discharges in N2O at different rf frequencies(PHYSICS OF PLASMAS, 2006-10) Lisovskiy, V.; Booth, Jean-Paul; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.This paper reports current-voltage characteristics and pressure-voltage transition curves from the weak-current a-mode to the strong-current g-mode for rf capacitive discharges in N2O at frequencies of 2 MHz, 13.56 MHz, and 27.12 MHz. At 2 MHz the rf discharge is mostly resistive whereas at 13.56 MHz and 27.12 MHz it is mostly capacitive. The weak-current a-mode was found to exist only above a certain minimum gas pressure for all frequencies studied [N. Yatsenko Sov. Phys. Tech. Phys. 26, 678 (19810] previously proposed that the a−g transition corresponds to breakdown of the sheaths. However, we show that this is the case only for sufficiently high gas pressures. At lower pressure there is a smooth transition from the weak-current a-mode to a strong-current g-mode, in which the sheaths produce fast electrons but the sheath has not undergone breakdown.
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