A high-power low-pressure iodine lamp pumped by glow discharge

We present the working characteristics of a high-power UV-VUV electric-discharge lamp filled with a working mixture of helium and iodine vapor (He-I₂) at a low pressure (0.1–1.5 kPa) and pumped by a dc glow discharge at a power of 15–200 W. The power of the total output UV radiation and the main emission peak at λ = 206.2 nm were studied as dependent on the electric power supplied to the glow discharge and on the partial pressure of helium in the He-I₂ mixture. The emission characteristics of the glow discharge plasma were studied in the spectral range from 200 to 350 nm. In this range, the lamp is operating predominantly on a resonance emission line of excited iodine atoms (λ = 206.2 nm, FWHM = 0.10–0.12 nm) and on a system of electronic-vibrational bands of excited iodine molecules with the main peak at λ = 342 nm. The contribution of the resonance emission due to excited iodine atoms to the total UV emission from the glow discharge plasma does not exceed 50%. The optimum partial pressure of helium is within 400–800 Pa. The total UV radiation power of the lamp operating in the optimum regime reaches 25 W at an efficiency of η ≤15%.     

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%.     

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.     

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.     

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.     

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.     

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.     

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.     

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 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.     

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.     

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%.     

Investigation of gas-dynamic processes in optical discharges with an ablating polymer wall in air and vacuum conditions

Experimental research results are presented on the formation dynamics and macrostructure of optical discharges of condensed matter of a polymer series ((C₂F₄) _n , (CH₂O) _n ) under the action of a femtosecond laser (τ _0.5 ∼ 45–70 fs) pulses (I ₀ ∼ 10¹³−10¹⁵ W/cm²) in the UV — NIR spectral region (λ ∼ 266, 400, 800 nm) under air and vacuum conditions. Electron density distributions in the near-surface area of the optical discharge, vapor expansion, and velocities of shock-wave front propagation are determined for the first time by precise laser pulse micro-interferometry with high spatial and time resolution. The correspondence is shown of the values of the laser ablation spectral-energy threshold, as determined by interference microscopy and the interferometry of a gas-plasma flow. An estimation technique for the total momentum of light-erosion gas-plasma flow in the sub-nanonewton range is proposed and implemented for the first time. The results of comparative analysis are presented on the laser radiation conversion efficiency at different stages of femtosecond optical discharges.     

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.     

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%.     

Inductively coupled RF oxygen plasma characterization by optical emission spectroscopy

Optical emission spectroscopy was applied for the characterization of inductively coupled RF oxygen plasma at pressures between 10 and 300 Pa. The plasma was generated with an RF generator at a frequency of 27.12 MHz and output power of 300 W. Spectra were measured in the range 200-1100 nm by an optical spectrometer. At high pressure, the main spectral features observed were the wavelengths of the atomic oxygen transitions at 777.2 and 844.6 nm. Molecular oxygen band at 762 nm was observed as well. The atomic emission intensity showed a maximum when the pressure was about 75 Pa, while molecular band intensity increased monotonically as the total pressure increased. On decreasing the oxygen pressure, other atomic and molecular features appeared in spectra, such as H atomic lines, molecular OH band, and O₂⁺ band. The behavior of spectral features was explained by collision phenomena in the ionized gas.     

The optical characteristics of plasma formed by laser erosion of CdGa2Se4 and CdGa2S4 crystals

The optical emission from fragments formed during a laser-induced erosion of the surface of CdGa₂Se(S)₄ single crystals was studied. The laser plasmas were generated by pulsed radiation of a Nd laser with a beam power density of (1–2)×10⁹ W/cm². The laser plasma exists in the form of a nucleus with a diameter of 2–3 mm, while no plasma torch is formed in the space above the target surface. In the 200–600 nm spectral range, the main emission lines observed in the spectrum of the plasma obtained from a laser-eroded CdGa₂Se₄ crystal corresponded to transitions from the lowest atomic energy levels of Ga(I), as well as to the intense transitions between the electron states of Se(II) and Se(III). The emission spectra of the plasma from a laser-eroded CdGa₂S₄ crystal surface exhibited a single intense line at 532.1 nm showing evidence of a prevailing contribution of the S(II) (4s–4p) transitions. The optical data agree with the results of the mass spectrometric analysis of the laser plasma generated from cadmium thiogallate crystals. The emission characteristics are of interest from the standpoint of the plasma diagnostics and optimization of the technology of laser sputter deposition of thin films with complicated compositions.     

A water-vapor electric-discharge vacuum ultraviolet source

The optical emission from a longitudinal dc glow discharge in water vapors (P=0.05–2.5 kPa) was studied in a wavelength range of λ=130–350 nm. It is shown that the discharge in low-pressure water vapors can be used as a source of the vacuum UV (VUV) radiation in the 140–190 nm wavelength range. As the vapor pressure was increased to 2.5 kPa, the emission intensity decreased by one-two orders of magnitude and the main peaks shifted to λ=286 and 306–315 nm. The bands of optical emission from the products of water decomposition agree in position with the emission band edges of the hydroxyl molecule. The obtained results are important for the development of a simple water-vapor electric-discharge VUV source.     

Optical properties of 2-(<Emphasis Type="Italic">p</Emphasis>-prolinol)-5-nitropyridine-fullerene system in the middle infrared range

The optical properties of 2-(p-prolinol)-5-nitropyridine (PNP) sensitized with fullerene C₆₀ have been studied in the middle IR range (λ=2940 nm). It is shown that materials based on the PNP-fullerene system can be used for limiting laser radiation in this spectral range.     

Characteristics and plasma parameters of a short-wavelength low-pressure discharge lamp

We have studied the working optical characteristics and electron kinetic coefficients of a short-wavelength, electric discharge exciplex-halogen UV-VUV lamp employing a mixture of argon and chlorine with a total pressure of P = 0.5–10 kPa. The lamp operates on a system of broadened electron-vibrational bands of ArCl (175 nm) and chlorine (200, 258 nm) molecules, which overlap to form a continuum in the spectral range of 160–260 nm. It is established that the optimum mixtures are those with p(Ar) − p(Cl₂) = (2–4)−(0.15–0.30) kPa. The average output power of the short-wavelength radiation is 1–2 W at an efficiency of ∼5%. The electron energy distribution functions (EDFs) and the discharge plasma parameters have been calculated by solving the Boltzmann equation for a gas mixture with the experimentally determined optimum composition in the range of E/P values from 1 to 200 V/(cm Torr), where E is the electric field strength and P is the total gas pressure. Using the obtained EDFs, the electron transport characteristics, specific discharge power losses for the main elementary processes, and rate constants of electron processes are determined.