UV emission from capacitive discharge in inert gas-iodine vapor mixture

We have studied the optical characteristics of capacitive discharge in binary mixtures of helium, neon, argon, and krypton with iodine vapor in a spectral range of 180–300 nm. It is established that the main power of UV radiation from the discharge plasma is concentrated in the emission lines at 183.0 and 206.2 nm. The intensity of emission due the spectral lines of iodine atom was optimized with respect to the inert gas type and partial pressure. The optimum results were obtained using He-I₂ mixture with partial pressures of helium within 0.8–2.0 kPa and iodine vapor below 50–60 Pa. Being excited with a trains of nanosecond current pulses at a repetition rate of 10–100 Hz, the capacitive discharge emitted pulses with duration not exceeding 400–500 ns.     

Bromine-iodine excimer electric-discharge lamp with continuous UV radiation spectrum

The optical characteristics of a small-size UV lamp filled with a working mixture of xenon and krypton with bromine and iodine vapor and pumped by longitudinal electric discharge have been studied. The lamp emits a resonance atomic line of iodine I* at 206.2 nm (with a full width at half maximum of 0.10 nm) and a continuum in the range 220–390 nm, which is formed by the emission bands of diatomic molecules [XeI(B-X), XeBr(B,D-X), Br₂(B-X), I₂(B-X), and IBr(B-X)]. The optimum partial pressure of iodine vapor is 100–200 Pa, that of bromine vapor ranges from 130 to 400 Pa, and that of heavy inert gases, from 400 to 800 Pa. The average total UV output radiation power was 10–12 W at an efficiency of 10–12%.     

A xenon-iodine electric discharge bactericidal lamp

We present the working characteristics of a continuous UV lamp emitting at λ=206 nm, pumped by a longitudinal glow discharge. The pressure of the working Xe-I₂ gas-vapor mixture was within 0.1–10 kPa. The power deposited in the discharge was varied within 10–130 W. The current-voltage characteristics, the emission spectra in a 200–600 nm wavelength range, the line emission intensity as a function of the power deposited in the discharge plasma, and the partial pressure of xenon in the lamp were studied. It is established that the lamp operates in the range of 206–342 nm on a resonance line of iodine at 206 nm and on the bands at 253 nm [XeI(B-X)] and 342 nm [I₂(B-X)]. Not less than half of the output UV emission power is concentrated in the bactericidal spectral interval (around λ=206 nm). The total UV emission power of the lamp reaches 6–7 W at an efficiency of ≤5%.     

The optimum characteristics of a halogen lamp pumped by transverse RF discharge

We report on the optimized characteristics of a small-size bactericidal lamp pumped by transverse RF (f=1.76 MHz) discharge, operating on a system of the molecular emission bands of chlorine in a wavelength range of 195–310 nm. The spectral characteristics of the plasma emission were measured and the intensity of chlorine emission bands were studied as functions of the total pressure and partial composition of a helium-chlorine mixture. Oscillograms of the pumping current and output radiation intensity were measured and the total output radiation power was determined. It is established that the lamp radiates predominantly in a bactericidal wavelength interval on an electron-vibrational transition at 200 nm in Cl₂** molecules. The optimum partial pressures of helium and chlorine are 100–300 and 90–120 Pa, respectively. The maximum output power of UV emission from the side cylindrical surface of the lamp reached 10 W. The lamp can be used in photochemistry, ecology, genetics, and medicine.     

Excited nitrogen molecule formation in a DC-glow-discharge-pumped excimer lamp

The plasma in an excimer lamp operating in the λ=258 nm [Cl₂(D′-A′)] and 175 nm [ArCl(B-X)] modes using an Ar-Cl₂ gas mixture excited with a longitudinal dc glow discharge was studied by the method of spectroscopic diagnostics. In the presence of small air admixtures (P≤30 Pa) in the working medium, the plasma exhibits the formation of excited nitrogen molecules decaying with the emission of molecular bands in the 193–271 nm wavelength range. The emission intensities of both molecular and excimer bands were measured and the conditions were determined under which the excited nitrogen molecules most significantly affect the optical characteristics of the discharge.     

The effect of water vapor on the characteristics of a pulsed-periodic ultraviolet radiation source

The effect of a small admixture of water vapor on the optical characteristics of an UV radiation source using a He-air-H₂O mixture as the working medium was studied. The gas mixture was excited in a short-pulse transverse volume discharge operating at a charging voltage of U _ch ≤10 kV. As the partial pressure of helium was varied in the 10–45 kPa range at an air pressure of P(air)=130 Pa and the water vapor pressure within P(H₂O)=50–100 Pa, the main optical emission from plasma in the UV wavelength range was concentrated in a broad band peaked at λ_max=309.7 nm and was two times greater than the intensity of the base emission bands of the nitrogen molecule in this spectral range (λ=337.1 and 315.9 nm, N₂(C-B)). Adding water vapor to the He-air mixture increases the spectral range of the UV source toward shortwave region, which is related to a spontaneous decay of the products of dissociation of water molecules.     

A Broadband Excimer-Halogen Emitter Utilizing Xenon Bromide and Iodide

The results are given of an investigation of the output characteristics of an electric-discharge excimer-halogen UV emitter utilizing a Xe/Br₂/J₂ mixture. A longitudinal glow discharge with an interelectrode spacing of 50 cm and inside diameter of the discharge tube of 1.4 cm is ignited at the working mixture pressure of 1 kPa and power input to the plasma of 10–350 W. A study is performed of the current-voltage characteristics of the discharge, plasma radiation spectra in the 190–350 nm range, and distributions of the brightness of radiation of molecules as a function of the pumping conditions, as well as of pressure and partial composition of the gas mixture. It is demonstrated that the plasma of the discharge being investigated is a source of broadband UV radiation in a system of bands of 253 nm XeJ, 282 nm XeBr, and 292–310 nm Br₂ ^*, which are joined by the radiation of resonance line of iodine atom with = 206 nm. The total power of UV radiation of plasma increases linearly with the electrical power of the glow discharge.     

The formation of excited chlorine atoms in a low-pressure transverse volume discharge

The characteristics of a transverse volume discharge (TVD) in chlorine at low pressures (P(Cl₂)=0.1–1.5 kPa) were studied. The excited chlorine atoms were formed in a 18×2.2× (0.5–1.0) cm volume using relatively low values of the capacitor bank charging voltage (U _ch ≤ 10 kV) in the pulsed discharge voltage source. The optical emission from plasma was studied in a spectral range from 500 to 900 nm. Homogeneous TVD pulses of short duration (τ; ≤ 100 ns) obtained under these conditions are of interest for use in UV-VUV lamps employed in pulsed plasmachemical reactors for dry etching of thin films. The density of excited atomic chlorine radicals can be monitored on medium-resolution spectrometers using the ClI emission lines with λ=725, 754, and 821 (2) nm.     

An effective high-power KrCl excimer barrier-discharge lamp

The effect of the pumping pulse power and shape on the discharge character and the efficiency of emission from KrCl* molecules (λ∼222 nm) is studied. In the coaxial quartz tube KrCl excimer lamps excited by a barrier discharge, the maximum emission efficiencies are observed for a discharge in the form of diffuse cones. Based on these results, an excimer lamp with an average output power of up to 100 W is created.     

Short-wavelength XeBr-Br gas discharge lamp

The output characteristics of a small-size gas-discharge lamp emitting in the 160–300 nm wavelength range are reported. The working medium—a mixture of xenon and bromine vapor—was excited in a longitudinal glow discharge in a quartz tube with an interelectrode distance of 100 mm. The emission spectrum is formed by the molecular lines of xenon bromide at 282 nm [XeBr(B-X)] and 220 nm [XeBr(D-X)] and the atomic resonance lines of bromine at 163.3 and 157.6 nm. An increase in the partial pressure of xenon in the working mixture from 130 to 800 Pa is accompanied by a decrease in the intensity of emission lines due to atomic bromine and an increase in the intensity of emission from xenon bromide molecules. The operation regime was optimized with respect to the energy supplied to the glow discharge and the working gas mixture pressure and composition. The optimum partial pressure of xenon is within 600–800 Pa, and that of bromine vapor, within 50–100 Pa. The average total VUV-UV output radiation power reached 7 W.     

High-power source of 200–350 nm spontaneous emission excited by unipolar current pulses

Spectral, energy, and temporal characteristics of pulse discharge in xenon have been experimentally studied. Upon passing from an oscillatory regime to unipolar pulses of discharge current, the power of emission in the wavelength interval 200–350 nm increases, while the emission pulse full width at half maximum (FWHM) decreases. A quartz pulsed discharge lamp excited by a generator based on high-current high-voltage diodes radiates in the 200–350 nm interval at a peak radiant intensity above 65 kW/sr and at a pulse FWHM ∼ 2 μs.     

Shortwave krypton-bromine excimer low-pressure lamp

The emission characteristics are reported for a small short-wavelength (UV) lamp filled with a krypton-bromine mixture and pumped by longitudinal glow discharge at a 100-mm distance between electrodes in a quartz tube with an internal diameter of 14 mm. The emission spectrum is formed by the resonance atomic lines of bromine (163.3 and 157.6 nm) and the molecular lines of bromine (Br₂) and krypton bromide (KrBr). An increase in the partial pressure of bromine in the working mixture from 50 to 270 Pa is accompanied by a decrease in the intensity of emission lines due to atomic bromine and leads to the formation of VUV-UV continuum based on the molecular bands due to Br₂ and KrBr. The operation regime was optimized with respect to the glow discharge current and the gas mixture pressure and composition. The optimum partial pressure of krypton is within 500–800 Pa, and that of bromine vapor is within 100–250 Pa. The average total VUV-UV output radiation power reached 5 W at an efficiency of 8–10%.     

A pulsed-periodic low-pressure volume discharge in a krypton-chlorine gas mixture

The initiation conditions and characteristics of a volume discharge in a krypton-chlorine mixture at low pressures (P≤1.0 kPa) were studied. It is shown that a constant voltage of U _ch 1.0 kV applied to a spherical anode-flat cathode system gives rise to a pulsed-periodic discharge with a pulse repetition rate of 1–50 kHz. The current-voltage characteristics of the discharge, the spectra of emission in a wavelength interval of Δ λ=130–350 nm, and oscillograms of the current and the total output emission intensity were studied as dependent on the partial composition and pressure of the krypton-chlorine mixture. It is shown that the discharge is a selective source of emission in the electronic-vibrational bands with λ=257 nm [Cl₂(D′-A′)], 222 nm [KrCl(B-X)], and 200 nm [C1₂**]. The volume discharge in the Kr-Cl₂ mixture can be used for the development of pulsed-periodic low-pressure excimer-halogen lamps.     

The emission characteristics of low-pressure water vapor discharge UV emitters

We have studied the characteristics of UV emission sources operating on low-pressure normal (H₂O) and heavy (D₂O) water vapor excited by periodic-pulsed and glow discharges. The emission in a 300–330 nm wavelength interval has been studied in detail for water vapor pressures ranging from 50 to 2500 Pa. A comparison of the characteristics of emission from discharge plasma at low (50–150 Pa) and elevated (2.0–2.5 kPa) water vapor pressures reveals significant differences in the character of emission spectra, which can be related to the different types of emitting species (hydroxy radicals versus small clusters of such radicals and water molecules). Discharge current and emission intensity pulses in the periodic-pulsed discharge regime have been measured.     

KrCl and XeCl exciplex glow discharge lamps with an output power of ∼1.5 kW

A high-power multisection cylindrical exciplex lamp pumped by a glow discharge is created. The energy, temporal, and spectral characteristics of the emission from KrCl* (λ～-222 nm) and XeCl* (λ～308 nm) molecules are studied. The average output UV radiation power is 1.6 kW (for 222 nm) and 1.1 kW (for 308 nm) at a power pumping efficiency of up to 14%.     

A high-frequency UV-VUV radiation source operating on a mixture of argon with chlorine molecules

We present the working optical characteristics of a short-wavelength electric-discharge lamp operating at 150–270 nm (UV-VUV spectral range). The working medium is a mixture of argon with chlorine molecules (Ar-Cl₂) excited in a high-frequency transverse discharge between a metal electrode and a semitransparent nickel grid with an interelectrode distance of 2.2 cm. The proposed UV-VUV radiation source operates on the broadened emission lines of chlorine (Cl₂) and argon chloride (ArCl) molecules, which form a continuum in the 150–270 nm wavelength range. The source operation was optimized depending on the pumping power and the pressure and composition of the Ar-Cl₂ mixture. For a discharge excitation power within 50–300 W, the optimum working media were Ar-Cl₂ mixtures with the partial pressures P(Ar) = 300?400 Pa and P(Cl₂) = 30?40 Pa. The average total output power of the UV-VUV radiation extracted from the optimized source amounted to 15 W.     

Pulsed microwave radiator for the band system λ=175 nm ArCl(B-X)/236 nm XeCl(D−X)/258 nm Cl2*/308 nm XeCl(B-X)

Parameters of a multiwave radiator pumped with transverse volume discharge in an Ar-Xe-Cl₂ mixture at a pressure of P=5–30 kPa were optimized. It is shown that, at a partial xenon pressure in the mixture below 0.4 kPa, the discharge may serve a multiwave radiation source operating on the electron-vibrational transitions with λ=175 nm ArCl(B-X), 236 nm XeCl(D-X), 258 nm Cl₂(D′-A′), and 308 nm XeCl(B-X). The emission line intensities have comparable values, which may be of interest for applications in the short-wave pulsed photometry, microelectronics, and photochemistry.     

Vacuum-UV emitter using low-pressure discharge in helium-water vapor mixture

The spectral characteristics of emission from plasma of periodic-pulsed capacitive discharge in a mixture of water vapor with helium have been studied in a spectral range of 140–315 nm. Dependences of the intensity of the characteristic emission lines of hydroxy groups in He-H₂O plasma on the partial pressure of water vapor at a helium pressure of p(He) = 2.6 kPa are presented. The results provide a basis for the creation of simple sources of vacuum-UV radiation with a cheap working medium based on water vapor.     

Bactericidal iodine lamp excited by capacitive discharge

A new capacitive discharge lamp is created in which the main contribution to the output radiation is due to the iodine atomic emission line at 206 nm. The lamp has an average output power at λ=206 nm reaching 6 W, an efficiency of 8% (with respect to the electric energy supplied to the discharge), and a working life exceeding 1700 h. The results of tests on Escherichia coli and Staphylococcus aureus bacterial cultures reliably confirmed the bactericidal action of radiation of the proposed lamp.     

A planar excimer-halogen radiation source pumped by transverse RF discharge

We present the characteristics of a planar source of wideband shortwave radiation pumped by transverse RF (f=1.76 MHz) discharge in a Kr/Xe/Cl₂ mixture (P≤500 Pa). The spectral characteristics of the plasma emission were studied in the wavelength interval of 130–600 nm. The oscillograms of the voltage, current, and output radiation intensity and the diagrams of the output power depending on the gas pressure, partial composition of the working gas mixture, and discharge power are presented. It is established that the source produces emission predominantly in the spectral interval of 170–330 nm, representing a system of the molecular emission bands XeCl(D, B-X), KrCl(B-X), Cl₂(D′-A′), and Cl₂**. For a maximum output power in the UV-VUV range, the optimum working gas mixture is Kr/Xe/Cl₂ with the partial pressures P(Kr)/P(Xe)/P(Cl₂)=150–200/150–200/20–40 Pa. The maximum power irradiated within a solid angle of 4π via two output holes with a total area of S≤ 100 cm² reaches 30–40 W. In the region of a threshold with respect to the transverse discharge initiation, there are narrow peaks of plasma emission that are probably related to the jumps in the density of electrons and the positive and negative ions at the boundary between the plasma and the RF discharge layer.