Emission characteristics and parameters of a glow discharge in an argon-xenon-chlorine mixture

We present the results of a study of the emission characteristics of a low-pressure longitudinal glow discharge in an Ar-Xe-Cl₂ mixture (p = 0.5–6.0 kPa) and numerical modeling of its plasma parameters as a function of the parameter E/P. We optimized the average emission power of the discharge in the spectral range 160–310 nm as a function of the discharge current, the pressure and composition of the gas mixture. The plasma parameters were calculated for the optimal mixture (according to experimental data) and included obtaining the dependences of the electron transport and energy characteristics, the power losses per unit pressure in the discharge going toward elementary electron processes in the plasma, and also the ionization and attachment coefficients as a function of the parameter E/P. The results of numerical modeling of the glow discharge parameters allow us to provide a qualitative basis for the emission distribution in the spectrum of a plasma based on an Ar-Xe-Cl₂ mixture. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 563–567, July–August, 2008.     

Source of far and vacuum ultraviolet radiation based on a transverse high-frequency discharge

We present the results of an investigation of a short-wavelength radiation source (Δλ = 130–350 nm) with excitation by a transverse high-frequency (f = 1.76 MHz) discharge based on a mixture of argon and chlorine (p = 100–500 Pa). We have studied the spectral characteristics of the plasma, the oscilloscope traces of the voltage, the current and emission of the discharge, the dependence of the power of the emission on the electrical power of the discharge, and also the pressure and partial composition of the Ar/Cl₂ mixture. The UV-VUV source emits in a system of broadened and overlapping ArCl(B/X), Cl₂(D′/A′), and Cl**₂ molecular bands. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 648–651, September–October, 2007.     

Emission properties of a pulsed-periodic barrier discharge initiated in helium-iodine and argon-iodine mixtures

The subject of investigation is the emission properties of a pulsed-periodic barrier discharge initiated by submicrosecond pulses (f = 40–1000 Hz) in He-I₂ and Ar-I₂ mixtures. The investigation is carried out in the spectral range 200–400 nm at a pressure of the working medium of 1–100 kPa and an iodine partial pressure of 130–200 Pa. The dependence of UV emission from the plasma of the barrier discharge at the 342 nm I₂(D′ → A′) band and the iodine atom spectral line at 206.2 nm on the argon and helium partial pressures, excitation pulses repetition rate, and charging voltage of the capacitor of a short high-voltage pulse modulator is optimized. The contribution of the 206.2 nm I* spectral line to the UV emission of the barrier discharge is estimated.     

Glow-discharge-pumped broadband ultraviolet lamp

The optical characteristics of a UV broadband lamp that was excited by a longitudinal glow discharge and operated on Kr—Br₂—I₂, Xe—Br₂—I₂, and Kr—Xe—Br₂—I₂ mixtures are investigated. The interelectrode spacing in the lamp is 10 cm, the inner diameter of a discharge tube being 14 mm. The current-voltage characteristics, the emission spectra of the plasma, and the dependence of the intensity of spectral lines (the amplitude of radiation bands) on the power that was pumped into the plasma based on mixtures of various compositions and pressures, as well as the radiation power in the spectral range from 200 to 390 nm, are studied. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 840–842, November–December, 2005.     

Emissivity of the pulsed capacitive discharge in helium-iodine and neon-iodine mixtures

The emission parameters of a pulsed capacitive discharge initiated in helium-iodine and neon-iodine mixtures are reported. The discharge plasma emits at wavelengths of 183.0 and 206.2 nm, which correspond to iodine atom spectral lines. The capacitive discharge is initiated in a cylindrical quartz tube with an electrode distance of 10 cm. The discharge radiation is optimized in exciting pulse repetition rate and helium and neon pressures in He(Ne)-I₂ mixtures. The optimal pressures of helium, neon, and iodine vapor fall into the ranges 0.8–2.0 kPa, 0.5–1.0 Pa, and ≤60 Pa, respectively.     

Short-wavelength emission characteristics of a longitudinal bromine vapor glow discharge in a quartz tube

The output emission characteristics are presented in the spectral range 150–350 nm for a longitudinal bromine vapor glow discharge in a quartz tube (inner diameter 1.4 cm, interelectrode distance 10 cm). Pressure of the working mixtures: P = 0.2–1.0 kPa. The emission spectrum of the lamp based on an He-Br₂ mixture consists of the 163.3 nm and 157.6 nm spectral lines of the bromine atom and a system of molecular bromine bands (170–300 nm). The total power of UV-VUV emission of the lamp based on an He-Br₂ mixture is 5 W max for efficiency <10%. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 816–819, November–December, 2007.     

Optical characteristics of a transverse discharge in neon at atmospheric pressure

We present the results of investigation into radiation of a pulsed transverse discharge in neon at a pressure of 10–200 kPa. Survey spectra of plasma radiation, time characteristics of radiation, and the effect of small impurities of water vapors and air on the optical characteristics of a neon plasma were studied. We show that at a pressure of residual gases at a level of 10 Pa intense OH*, NO*, and N _* ² bands are observed in radiation of the plasma of a nanosecond transverse discharge in Ne against the background of continuous plasma radiation, and in the spectral region with λ>400 nm radiation was observed on the H_β 486.1 nm and NeI 585.3 nm lines, and (when P≥100 kPa) on the line at the 3s–3p-transitions of a Ne atom. The radiation intensity of the third continuum of neon increases with pressure and with energy contribution to plasma, with its maximum being located in the VUV spectral region (λ _max <200 nm). To whom correspondence should be adressed. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 5–10, January–February, 1999.     

Output characteristics and parameters of the plasma from a gas-discharge low-pressure ultraviolet source using helium-iodine and xenon-iodine mixtures

The output characteristics and parameters of the plasma of a powerful gas-discharge source of UV radiation are studied. The UV source uses He-I₂ and Xe-I₂ mixtures and is excited by a longitudinal glow discharge. The pressure of the gas mixtures is varied from 100 to 1500 Pa, and the discharge power falls into the range 15–250 W. The source (lamp) emits in the spectral interval 200–390 nm, which covers the spectral line of the iodine atom at 206.2 nm, the spectral band of XeI(B-X) with a maximum at 253 nm, and the spectral band of with a maximum at 342 nm. For He(Xe)-I₂ mixtures at a pressure of 800–1000 Pa (this pressure range is near-optimal according to our experimental data), the electron energy distribution functions and the electron kinetic coefficients as functions of parameter E/N (E is the electric field strength, and N is the particle concentration in the discharge) are calculated. The calculated plasma parameters are used in the qualitative analysis of key electronic processes in the plasma of an exciplex halogen UV source and will be subsequently employed in numerical simulation of the process kinetics and output characteristics of a UV source based on helium-iodine or xenon-iodine mixtures.     

Emission characteristics of a glow discharge plasma based on a mixture of helium with chlorine molecules

We present the results of a study of the emission characteristics of a longitudinal glow discharge based on a mixture of helium and chlorine. Study of the emission characteristics of the discharge showed that it emits most efficiently in the bands of the chlorine molecule with maxima at 200 nm and 258 nm in an He-Cl₂ mixture (P = 0.2–0.3 kPa). We present the optimization of the average emission power of a UV emitter as a function of the glow discharge parameters, the pressure, and the composition of the working gas mixture. Based on solution of the Boltzmann equation for the electron energy distribution function in a discharge based on the optimal mixture (according to experimental data), we calculated the power losses per unit pressure going toward elementary processes, the electron transport characteristics, the ionization and attachment coefficients as a function of the parameter E/P. The calculated parameters of the plasma for the UV emitter allowed us to provide a basis for the qualitative pattern of physicochemical processes in the studied plasma. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 121–124, January–February, 2008.     

Spectral characteristics of the emission from a barrier discharge plasma based on an Ar–H2O mixture in the UV spectral region

We present the results of a study of a barrier-discharge plasma in an Ar–H₂O mixture in the UV region of the spectrum (200–500 nm). The saturated water vapor pressure was varied over the range 2.0–2.5 kPa. A comparative study of the spectral characteristics of the plasma based on water vapor and the Ar–H₂O mixture showed that the intensity of the emission of the A → X band of the OH^● radical increases three-fold in the mixture of water with argon.     

Bipolar atmospheric-pressure corona discharge in a He/H2 mixture

Results are presented from a study of the characteristics of a steady-state plasma in a He/H₂ mixture at high pressures. The plasma is formed in the outer region of a multielectrode corona discharge. It is shown that molecules of helium hydride form in such a medium, and their decomposition is accompanied by continuum emission in the 350–650 nm region. The corona discharge is distributed over the length and can be used in systems for the transverse electric circulation of the working medium of atmospheric-pressure plasma radiation sources. The reference spectra of the plasma emission and the dependence of the relative intensity of the lines and the brightness of the bands of He ₂ ^* on the value of the discharge current, pressure, and composition of the working mixture are investigated. Zh. Tekh. Fiz. 69, 33–37 (July 1999)     

Synthesis of nanocrystalline titanium dioxide films in a cylindrical magnetron-type gas discharge and their optical characterization

The plasma-dynamic and spectral characteristics of a cylindrical magnetron-type gas discharge are studied experimentally. The radiation spectrum of the plasma is recorded in real time in the range 350–820 nm. Appropriate conditions for synthesis of TiO₂ binary compound are found. They are provided by maintaining the intensities of the spectral lines of reactants and a plasma-forming gas at a desired level. The feasibility of monitoring the TiO₂ film synthesis conditions from the spectral characteristics of the discharge plasma and from the variation of the discharge voltage is considered. Ellipsometric and spectral data for nanocrystalline titanium dioxide films indicate that the refractive index of the film depends on its thickness.     

X-ray generation in low-voltage vacuum discharges

The dynamics of x-ray emission from a low-voltage laser-induced discharge was studied with the aid of a picosecond x-ray streak camera. Directed x-ray emission in the spectral range from 100 eV to 10 keV in the form of point sources and thin layers with lifetimes ranging from 30 ps to 1 ns was observed in a low-voltage vacuum discharge (U=150 V) initiated by a picosecond laser beam. X-ray emission from a discharge was detected with a time delay (1–20 ns) relative to ignition by the laser beam in order to prevent the radiation of the laser plasma from entering the detector. Detection of directed x-ray emission in a low-voltage vacuum discharge is demonstrated. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 622–627 (10 May 1998)     

Compact X-ray radiograph based on a plasma gun

The results of the experiments on the formation of a plasma emitter with small spatial dimensions for pulsed radiography in the soft X-ray spectral range are presented. Emitting hot plasma was formed as a result of compression of the plasma jet by a current pulse with amplitude I _m = 215 kA and rise time T _fr = 200 ns. For the jet formation, we used a plasma gun based on the arc discharge (I _m = 8.5 kA and T _fr = 6 μs) initiated by breakdown over the surface of a dielectric in vacuum. The experiments were carried out with aluminum, tin, copper, and iron plasma jets. A single emitter, i.e., point Z-pinch (PZ-pinch), was formed when an interelectrode gap of a high current generator of 1.3–1.5 mm was used. The smallest spatial dimensions of the emitting region were obtained with the use of aluminum and tin. For a tin jet, the diameter of the emitting region was 7 ± 2 μm and its height was 17 ± 2 μm. The emission pulse duration at half-height was 2–3 ns. The total emission yield per pulse in the spectral range 1.56–1.90 keV was 30–50 mJ for the aluminum pinch and 10–30 mJ for the tin pinch. The developed method makes it possible to carry out radiographic examination of microobjects (including biological ones) 1–1000 μm in thickness, with spatial (10–20 μm) and time (2–3 ns) resolution.     

Spectroscopic investigation of the plasma of a high-current diffuse discharge in He/Ar/CF2Cl2(CCl4) mixtures

Survey emission spectra in the region of 190–600 nm and time and service-life characteristics of a transverse nanosecond discharge in He/Ar/CF₂Cl₂(CCl₄) mixtures at a pressure of 10–100 kPa are investigated. In the emission spectra, excited products of the decomposition of freons—C₂(A−X), CN(B−X), Cl ₂ ^* , C^*, Cl^*, and Cl^+*— and the emission of ArF at λ=193 nm are revealed. The emissions of Cl ₂ ^* at λ=258 nm and ArF at λ=193 nm were the most intense. The discharge in the He/Ar/CF₂Cl₂ mixture is a multiwave emission source with λ=258 nm Cl ₂ ^* 193 nm ArF, and probably, 175 nm Arcl. It is of interest for applications in UV-VUV-range pulse photometry. The duration of the emission on Cl ₂ ^* , ArF, ArI, ClI, and ClII transitions in the discharge in the Ar/CF₂Cl₂ mixture (P=10–20 kPa) was 200–300 nsec. With adding He and increasing pressure to 100 kPa the duration of the emission decreased by a factor of 1.5–2. The basic mechanisms of the formation of Cl₂, ArF, and CN(B) molecules in the transverse-discharge plasma are considered. Uzhgorod State University, 46, Pidgirna Str., Uzhgorod, 294000, Ukraine. Translated from Zhurnal. Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 241–246, March–April, 1999.     

Emission of cyan upon excitation of nitrogen,air, and N<Subscript>2</Subscript>-CH<Subscript>4</Subscript> mixture by discharge pulses in an inhomogeneous electric field

We have studied spectral and amplitude-time characteristics of the emission by nitrogen, air, and the N₂-CH₄ mixture upon excitation by nanosecond and microsecond high-voltage discharge pulses in an inhomogeneous electric field in the pressure range of 0.01–3 atm. In the pulsed and pulse-periodic discharge regimes, we have observed emission bands of the violet system of cyan, the transition B ²Σ⁺ → X ²Σ⁺, which were comparable in intensity with bands of the (2⁺) system of nitrogen. We show that, in the pulsed regime, the highest intensity of the violet system of cyan is observed in the N₂-CH₄ mixture. We show that, in the pulse-periodic discharge in nitrogen with a small amount of a carbon-containing admixture, upon contracting the discharge, the efficiencies of formation and emission of the violet system of cyan considerably increase. We confirm that admixtures of oxygen to nitrogen lead to suppression of the emission of the violet system of cyan molecules.     

VUV lamp based on mixtures of inert gases with water molecules pumped by a pulsed-periodic capacitive discharge

The spectral characteristics of the emission in the 140-315 nm range from pulsed-periodic capacitive discharges in mixtures of water vapor and helium and argon are described. In the VUV the most intense bands have maxima at λ = 156.0, 180.3, and 186.0 nm, and in the region of 300–315 nm, at λ = 312.1 and 313.4 nm. The brightness of the emission from the capacitive discharge plasma is optimized with respect to the partial pressures of helium, argon, and water vapor. The electron kinetic coefficients of discharges in argon and water vapor mixtures are calculated for E/N = 1–1000 Td.     

Ultraviolet radiation sources on (H2O,D2O) water vapor

Emission characteristics of ultraviolet (UV) radiation from water vapor (H₂O, D₂O, and a mixture of H₂O and D₂O vapors) excited by pulse-periodic discharges with open electrodes, as well as electrodes outside the discharge tube (capacitive discharge), are presented. Radiation is studied in a spectral range of 175–350 nm. The emission characteristics of a UV radiation source based on vapors of ordinary and “heavy” water, as well as the results of optimization of brightness of radiation bands from the OH and OD radicals as functions of pressure and the composition of the He-H₂O and He-D₂O mixtures, are reported.     

Electrical and optical characterization of pulsed plasma of N<Subscript>2</Subscript>–H<Subscript>2</Subscript>

This paper considers the electrical and optical characterization of glow discharge pulsed plasma in N₂/H₂ gas mixtures at a pressures range between 0.5 and 4.0 Torr and discharge current between 0.2 and 0.6 A. Electron temperature and ion density measurements were performed employing a double Langmuir probe. They were found to increase rapidly as the H₂ percentage in the mixture was increased up to 20%. This increase slows down as the H₂ percentage in the gas mixture was increased above 20% at the same pressure. Emission spectroscopy was employed to observe emission from the pulsed plasma of a steady-state electric discharge. The discharge mainly emits within the range 280–500 nm. The emission consists of N₂ (C-X) 316, 336, 358 nm narrow peaks and a broad band with a maximum at λ_max = 427 nm. Also lines of N₂, N₂ ⁺ and NH excited states were observed. All lines and bands have their maximum intensity at the discharge current of 0.417 A. The intensities of the main bands and spectral lines are determined as functions of the total pressure and discharge current. Agreement with other theoretical and experimental groups was established.     

Radiative characteristics and kinetics of processes in low-pressure gas-discharge lamps based on a mixture of helium and iodine vapors

The UV radiation of glow- and capacitive-discharge lamps based on mixtures of inert gases with iodine vapors are optimized in the spectral range of 175–360 nm, in which working helium-iodine mixtures of different compositions are used. The most intense spectral lines in the bactericidal region of the spectrum were the atomic lines of iodine (183.0, 206.2 nm), and in the region of 320–360 nm, emission of the spectral band of an iodine molecule prevailed with a maximum at λ = 342 nm. For a capacitive lamp with a casing opaque in the spectral range λ < 250 nm, the main part of the plasma emission power is concentrated in the A′-D′ band of an iodine molecule with a maximum at 342 nm. The emission brightness of this lamp is optimized in iodine molecule transitions depending on the partial helium pressure. We present the results of simulating the kinetics of processes in a glow-discharge plasma in mixtures of He, Xe, and iodine vapors. We establish the dependence of the main part of the emission intensity of the 206.2 nm spectral line of an iodine atom and the 342 nm band of an iodine molecule on the helium pressure in a glow-discharge lamp operating on a He-I₂ mixture.