Proceedings Volume 5483

Atomic and Molecular Pulsed Lasers V

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Proceedings Volume 5483

Atomic and Molecular Pulsed Lasers V

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Volume Details

Date Published: 3 May 2004
Contents: 6 Sessions, 44 Papers, 0 Presentations
Conference: Atomic and Molecular Pulsed Lasers V 2003
Volume Number: 5483

Table of Contents

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Table of Contents

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  • Gas and Plasma Lasers
  • Metal Vapor Lasers
  • Dye Lasers and Photoprocesses in Complex Organic Molecules
  • Physical Processes in Gas Lasers
  • Laser Systems and Applications
  • Incoherent UV and VUV Sources and Laser Output Conversion
Gas and Plasma Lasers
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Study of fission-fragment excited xenon laser in He-Xe, Ar-Xe, and He-Ar-Xe mixtures
A. A. Abramov, S. P. Melnikov, A. Kh. Mukhamatullin, et al.
Data on energy and threshold characteristics of xenon laser in the He-Xe (2.65 μm), Ar-Xe (1.73 μm), and He-Ar-Xe (2.03 and 2.65 μm) mixtures have been measured as a function of xenon partial pressure and output mirror reflectivity. Investigations were carried out using LUNA-2M setup irradiated by neutron flux of VIR-2M pulse reactor with pulse duration of about 3 ms. Using the experimental data and Rigrod model, small-signal gains and saturations intensities were determined.
Kinetics of CO first negative system excitation by ionized radiation
Investigation of the possibility of the quasicontinuous UV carbon monoxide first negative system laser development is interesting with the fact that quantum efficiency for 0-0 transition (λ = 219 nm) is 13.3%. H2, D2, Kr have high values of the deactivation rate constants of X2 Σ+ level. So the possibility of quasicontinuous laser on B-X transition of CO+ is determined by the ratio of the upper and lower laser levels quenching rates of H2, D2 molecules, Kr atoms. In the present work the luminescence spectra of gas mixtures with carbon monoxide under α-particle excitation are investigated. CO+ (B) quenching rate constants are obtained from dependence of the CO first negative system intensity on gases partial pressure in He+CO+H2 (D2, Kr) mixtures. At the analysis of experimental dates the population of the upper level during He2+-CO charge exchange was taken into account. Efficiency of B2 Σ+u, v=0 level population was defined by the ratio of the intensities of 1- system of N2 and Baldet-Johnson system in He-N2 and He-CO mixtures. The upper limit for the CO+ (B) quenching rate constant in collisions with H2(D2, Kr) is estimated as: kq<10-10 cm3 s-1. The results indicate the possibility of the efficient quasicontinuous laser action on the carbon monoxide first negative system in UV spectral region under ionized radiation source pumping.
Efficient long-pulsed XeCl lasers
Evgenii H. Baksht, Jingry Liu, Alexei N. Panchenko, et al.
Development of a long-pulse spark preionized XeCl-lasers pumped by a self-sustained discharge using a double-discharge circuit is reported. The pre-pulse is formed by novel generator with an inductive energy storage and semiconductor opening switch. The lasers produce up to 1-1.5 J in a pulse with total duration up to 500 ns and total efficiency up to 1.5-2%. Circuit for the discharge current correction is suggested for further extension of the optical pulse. The laser producing 300 ns (FWHM) was used as a master oscillator in a powerful XeCl-laser system.
Pulsed repetitive CO2 laser pumped by longitudinal discharge
Igor D. Kostyrya, Victor M. Orlovskii, Victor F. Tarasenko, et al.
Experimental results obtained on the pulsed repetitive CO2 laser pumped by a longitudinal discharge are reported. The laser pumping system included both the inductive energy storage with semiconductor opening switch and capacitive energy storage. The average radiation power of 300 mW was reached at the pulsed repetitive rate of 10 Hz. The duration of radiation pulse at FWHM was 60 μs, and the intrinsic efficiency was 5,5%. It has been shown that the radiation energy in a pulse at this parallel-flat cavity laser is sufficient for glass marking.
Efficient non-chain discharge HF and DF lasers
Effect of pumping pulse duration and specific input energy on the output of discharge non-chain HF (DF)-lasers is studied using excitation by inductive and LC-generators. Experimental conditions providing maximal performance of discharge non-chain HF- and DF-lasers are determined. High discharge uniformity obtained with the use of special shaped electrodes along with uniform UV preionisation was found to be key parameter for improving efficiency of discharge HF (DF)-laser. Intrinsic efficiency of HF and DF lasers up to ηin~10 % and 7%, respectively, is obtained in the SF6-H2(D2) mixtures. With the LC-generator, maximal total efficiency of the lasers up to η0=6% was obtained and the output over 1 J was realized.
Investigation on parallel spark array pre-ionization TEA CO2 laser
Majid Aram, F. Soltanmoradi, A. Behjat
Operation of a TEA CO2 laser with parallel spark array pre-ionization is investigated. Low repetition rate pulsed laser has been made having integrated pre-ionization and peaking circuits. The effect of gas mixture, applied voltage and capacity of the main, peaking and preionization capacitors on output power of the laser are presented. Total efficiency up to 7% was obtained and although the fraction of the He in gas mixture was only 58% stability of discharge was good (2 arc in 55 discharges).
Discharge-pumped XeCl laser triggered by e-beam
Output radiation performances of XeCl laser having 5.5 1 active medium volume depending on electric circuit parameters, intensity and uniformity of preionization are researched. The maximum output radiation energy of 7 J and pulse duration of 160 ns were obtained only in the presence of modulation of discharge current. It is shown that first of all laser efficiency depend on preionization homogeneity and not from its intensity. The largest laser output realized only in case the small percentage of Xe in gas mixture (≤0.25%).
Wide-aperture electric-discharge XeCl lasers
Ivan Konovalov, Valery F. Losev, Jingry Liu, et al.
Experimental results of long-pulse generation in X-ray preionized XeCl lasers with the 9x7 cm2 and 5.4x3 cm2 apertures are described. The lasers operate in the Ne-Xe-HCl mixture with the pressure up to 4 atm. Paper-oil pulse forming lines and a rail-gap switch for the discharge pumping were used. A 3.5 and 10 J output with the optical pulse duration of 250-300 ns (FWHM) has been extracted.
Peculiarities of short pulse electrical discharge XeCl laser
Yu. I. Bychkov, Valery F. Losev, Yury N. Panchenko, et al.
This paper reports on experimental results and simulation of XeCl-laser with short laser pulse duration. Experimental investigation was aimed at obtaining of maximal lasing power and efficiency. The processes taking place in plasma and in resonator were simulated. Temporal evolutions of plasma particle density as well as simulation rates of processes of ionization, recombination, attachment and formation of XeCl molecules in excited states were obtained. Simulation dependencies have been analyzed; mechanisms of initial parameter effect on lasing power have been established.
Waveguide pulsed gas lasers
Vladimir V. Salmin, Alexey A. Nekrasov, Alexander Sergeevich Provorov
Results of investigation of processes in waveguide pulsed gas lasers on atomic and molecular transitions are presented. Conditions of population inversion forming in N2(337 nm), XeCl, and Ne-H2(585 nm) lasers excited by longitudinal and barrier discharges in thin cells with various diameters were investigated. In the thin capillaries, significant changes of discharge forming conditions due to variation of Paschen’s curve have been observed. Particularly, in the capillaries with diameter less than 120 μm, optimal conditions of electronic temperature for the excitation of nitrogen laser at the self-breakdown have been achieved. We obtained the generation and investigated dependencies of an output power on gas pressure in the self-breakdown nitrogen laser. We studied the efficiency of XeCl excimer molecules formation in the plasma of the barrier discharge. Conditions required for efficient formation of excimer molecules in the plasma of barrier discharge was found. By double pulse technique the amplitude-frequency characteristics of efficiency of XeCl excimer molecules formation in the plasma of the barrier discharge were tested. Up to the frequency 30 kHz, there was no significant decrease of second pulse amplitude. We studied the dependence of efficiency of luminescence at the transition 3p’[1/2]0-3s’[1/2]0 of Ne (585,3 nm) on the gas pressure and the charging voltage of storage capacitors in pure Ne or with H2 additions in following ratios Ne:H2 (3:1, 2:1) with excitation by longitudinal discharge in narrow capillary 500 μm. The saturation of luminescence intensity occurs at the high pressure was found. The decreasing of luminescence at the additions of hydrogen was observed.
Metal Vapor Lasers
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Mechanism of pulsed inversion in a process of ion-ion recombination
Gueorgii G. Petrash, Konstantin I. Zemskov
Pulsed ion-ion recombination lasers can have high output power and efficiency if it will be possible to realize idealized mechanism of inversion suggested in our previous publications. How close it will be possible to come to realization of the idealized scheme depends on the proper choice of the active medium components (metal, buffer gas, electronegative molecule} as well as corresponding conditions of excitation and recombination. Some possible pairs of positive and negative ions of several metals with negative ions of Br, Cl, and I are discussed.
Mathematical modeling of ion recombination strontium vapor laser
Gennady D. Chebotarev, Oleg O. Prutsakov, Evgeny L. Latush
In the present work, a self-consistent model of the He-Sr recombination laser is developed. With this model one can calculate plasma parameters and laser characteristics in pulsed-periodic regime and also carry out multiparametric optimization of the laser. The calculations carried out by the model show that under a wide range of conditions (pHe=3 Torr-3000 Torr) the model allows to trace rather precisely all trends in the behavior of plasma parameters and laser characteristics. The calculations of laser characteristics carried out for 7 active elements with different geometry (la=9-70 cm, d =0.3-1.55 cm) show good agreement with experiment. The developed model can serve as a convenient tool for investigating kinetics of the active medium of the He-Sr laser.
Kinetics of active media of He-Zn+, He-Cd+, He-TI+, and Ne-In+ hollow cathode lasers and new laser lines
Igor G. Ivanov
The results of the theoretical and experimental study of the Zn+, Cd+, Tl+ and In+ ion levels population, gain and laser output power dependencies on the variation of hollow cathode discharge (HCD) parameters are presented. Pumping of excited metal ion levels goes through the thermal energy charge-transfer (CT) reaction between ground state buffer gas ions and neutral metal atoms, and second-kind collisions of HCD slow plasma electrons and atoms with excited metal ions, in redistributing the population amongst excited levels. A detailed kinetic model for negative glow plasma of HCD is based on affirmation that the total CT pumping rate for all metal levels is equal to buffer gas ionization rat and does not depend on CT cross section. Model uses the metal ion levels partial CT cross-section values which calculated based on Landau-Zener theory and Vigner spin rule and corrected accounting the experimental data, and uses the calculated transition probabilities in the Zn+, Cd+, Tl+ and In+ spectra in Coulomb approach taking into account the resonant trapping. The numerical calculations were made for the typical electron temperature (0,2...1eV) and density (0...1016 cm-3), and other discharge parameters of the HCD laser plasma. The results of calculations for known laser transitions are in a good agreement with the experimental data and predict the laser action and laser parameters values at cw and pulsed regime of HCD for 7 new Zn+ laser transition (0,317...13,7 μm) in He-Tl mixture, for 15 new Cd+ laser transition (0,53...1,92 μm) in He-Cd mixture, for 45 new Tl+ laser transition (0,318...18,83μm) in He-Tl mixture and for 27 new In+ laser transition (0,294...11,08μm) in Ne-In mixture.
On the possibility of lasing on new transitions of Sr II under conditions of strongly nonstationary recombination kinetics
Evgeny L. Latush, Oleg O. Prutsakov, Gennady D. Chebotarev
A search for new laser transitions is carried out in the spectrum of Sr II by using a mathematical model of the He-Sr recombination laser. The calculations revealed that under strongly non-stationary conditions it is possible to obtain a population inversion and lasing at the leading edge of the recombination pumping pulse on the ultra-violet transitions 52D3/2,5/2→52P1/2,3/2Sr II (λ = 338.1 and 346.4 nm). In this regime, the inversion arises as a result of transient processes at the establishing of populations of laser levels and it exists several nanoseconds, similar to that of self-terminated lasers.
The influence of HBr additives on breakdown characteristics of Ne-H2-Cu laser mixture
Gueorgii G. Petrash, Vladimir V. Rybkin
Stationary criterion of the Ne-H2-Cu-HBr laser mixture breakdown has been calculated using solutions of Boltzmann kinetic equation for electron energy distribution function (EEDF). It was found that increase of HBr molar fraction in the mixture leads to increase of breakdown voltage and, as a consequence, to more favorable ratio of rate constants of electron excitation of 2P (upper laser) and 2D (lower laser) atomic copper levels. Increase of Cu molar fraction in the mixture also can lead to increase of breakdown voltage due to an influence of electron collisions with copper atoms on the process of EEDF formation.
Effect of an external magnetic field on the output power of a copper bromide laser
An experiment for increasing the relaxation rate of the lower laser level of energy in a CuBr laser has been performed by applying a variable axial external magnetic field (EMF). A CuBr laser was employed. The effect of an axial EMF on the output power of the laser under different charging voltages and buffer gas pressures has been studied. We demonstrate that by applying an axial EMF, the output power of the laser can be optimized. The increase of the buffer gas pressure has a negative effect on this optimization. Simulation of the excitation electric field also shows that, by applying an EMF, attenuation of the electric field in radial direction and the delay between the electric field on the tube axis and the tube wall decreases.
Efficiency of charging circuit for metal vapor lasers
V. V. Tatur, P. V. Vybornov
Results are presented of investigation of characteristics of charging circuit for metal vapor lasers that is used for stabilization of power contribution into gas discharge tube. The circuit is shown for voltage stabilization on a reservoir capacitor that is used in transistor laser excitation source. The technical and exploitation advantages of this circuit are described.
Dye Lasers and Photoprocesses in Complex Organic Molecules
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Dichromatic laser photolysis of eosin in solid gelatinous matrix
A. G. Sizykh, E. A. Slyusareva
The laser irradiation of the thin films of solid solution of eosin in gelatinous matrix in the first and some upper dyes absorption bands leads to decrease of films optical density due to reaction of photoreduction. In the paper the kinetic of photoreduction of the dye eosin K in polymeric matrix in three cases of irradiation was experimentally investigated: a) irradiation by N2 laser (λ=337nm, second band of absorption, π=2 nsec, repetition rate-100 Hz, average power-2,2 mW), b) irradiation by Ar-laser (λ=488 nm, first band of absorption, 6,5-12 mW), c) under a simultaneous action of both Ar and N2-lasers. It was demonstrated that the most effective reaction of photoreduction took place in case of direct populating of upper singlet states with probable following nonradiative transition into equienergetic triplet states (energy ranges 35000-45000 sm-1).
Study of cresol phototransformations in neutral and acidic medium
T. V. Sokolova, Irina V. Sokolova, Edward A. Sosnin, et al.
It is well known that pH value and excitation energy have a directly impact on photolysis rate of phenols under Hg-lamp irradiation and oxidation process. The purpose of the current study is the research of o-cresol and para-cresol photolysis in acidic medium under various spontaneous radiation sources irradiation. Photochemical degradation was carried out through a high pressure mercury lamp OΚH-11M, and also with a new capacitive discharge excilamps on working molecules KrCl* (λ~222 nm) and XeBr* (λ~283 nm). Exposure time was varied from 1 to 40 minutes that corresponds radiation doses from 0.5 to 20 J/cm2. A comparison between phototransformations under different light excitation shows that cresol aqueous solutions acidation leads to increase of phototransformations efficiency. It was been found that both in neutral, and in acidic medium the photodecomposition of cresols is carried out more effectively under KrCl-excilamp irradiation.
Electron impact excitation of carbazole vapor
Vladimir A. Andreev, Anatoly L. Ivanov, Sergey M. Kazakov, et al.
With the help of electron impact spectrometer, energy loss spectra for carbazole vapour were measured in the energy range of the incident beam of electrons from 4 to 50 eV. Both optically resolved transitions S0-Sn and the forbidden transition S0-T1 were registered. Besides, spectra of fluorescence of molecules excited by electron beam with energy from the process threshold up to 500 eV were investigated and optical excitation functions of fluorescence band were measured.
Physical Processes in Gas Lasers
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On the mechanism of the runaway of electrons in a gas: the universal escape curves for He, Xe, N2
Sergey I. Yakovlenko, A. N. Tkachev
Basing on the simple form of the energy conservation law and taking into account a multiplication of electrons, we show that the Townsend mechanism of electron multiplication in a gas is valid at sufficiently large interelectrode distance even at so large values of an electric field strength, when it is possible to neglect ionization friction. Correspondingly, the runaway electron producing in a gas is determined not by the local criteria accepted presently, but by the ratio of interelectrode distance and the characteristic electron multiplication length. Basing on numerical simulations for nitrogen gas we show that the critical discharge voltage Ucr(pd), at which the runaway electrons begin prevail, is a function of the product of the interelectrode distance by the gas pressure pd. This function (escape curve of Ucr-pd dependence) separates the area of an effective multiplication of electrons and the area, in which electrons escape discharge gap not having time to be multiplied. The curve Ucr(pd) has the upper and lower branches. Using Ucr(pd) we obtain the analog of well-known Paschen curve, which describes additionally the absence of a self-sustained discharge at a high voltages sufficiently rapidly supplied across the electrodes. Escape curves for helium, xenon and nitrogen are presented.
Electron beams formation in helium-filled diode under atmospheric pressure
The formation of a beam of runaway electrons in a diode filled with helium at a pressure from 0.1 to 760 Torr was studied under conditions of a pulsed (4 ns) high (200 kV) voltage applied to the discharge gap. The experimental data results indicate that the electron beam is generated either at a large strength of electric field, when the fraction of runaway electrons is large, or in the field of low strength, where intensive electron multiplication takes place. In the latter case, cathode plasma propagates to anode at high velocity, at that with electrical field distribution in gas diode area the critical value of E/p is reached either due to geometric quotient leading to formation of nanosecond and subnanosecond electron beams. The electron beams obtained in the helium-filled diode had the current amplitude of up to 200 A (corresponding to the current density above 20 A/cm2) at electron energy of ~130 keV.
Formation of high-current electron beams in dense gases
Victor F. Tarasenko, Sergey I. Yakovlenko, Victor M. Orlovskii, et al.
Subnanosecond electron beams with the record current amplitude (~70 A in air and ~200 A in helium) were produced at the atmospheric pressure. The optimal generator open-circuit voltage was found for which the electron-beam current amplitude produced in a gas diode was maximal behind a foil. It was established that electron beam was produced at the stage when the cathode plasma closely approaches anode. It was shown that a high-current beam can be produced at high pressures because of the presence of the upper branches in the curves characterizing the electron-escape (runaway) criterion and the discharge-ignition criterion (Paschen curve).
Subnanosecond electron beam in air under atmospheric pressure
Victor F. Tarasenko, Sergey B. Alekseev, Igor D. Kostyrya, et al.
This paper reports on experimental study of subnanosecond e-beam formed in air under atmospheric pressure. An electron beam with amplitude of ~ 170 A with duration at FWHM ~0.3 ns has been obtained. Based on beam temporal characteristics and discharge spatial characteristics, the critical fields were supposed to be reached at plasma approach to anode. Simultaneously, the sharp high-energy pulse of e-beam current is generated. Of critical importance is cathode type and plasma protrusions occurred on the cathode. It is shown that in order to get maximum e-beam in gas diode, the discharge in gas diode should be volume.
Properties of plasma of volume nanosecond high-pressure discharge formed in non-uniform electric field
Victor F. Tarasenko, Sergey B. Alekseev, Igor D. Kostyrya, et al.
Properties of plasma produced in volume nanosecond high-pressure discharge and its formation conditions under elevated pressure in air, nitrogen, krypton, argon, neon and gas mixtures Ar-N2, Ar-Xe, CO2-N2-He in the gap with the cathode having small curvature radius have been investigated. Time-amplitude characteristics and radiation spectra of plasma in different gases in the range of 230-600 nm were defined. Lasing in the gas mixture Ar-Xe at active length of 1.5 cm has been achieved by excitation through volume nanosecond high-pressure discharge. Comparison of spectral radiation in nitrogen, krypton, argon, and neon under pumping of mentioned gases by volume discharge in non-uniform electric field, by nanosecond e-beam, and by volume pulsed discharge in the uniform electric field with high initial voltage was made. Lasing has also been obtained in the gas mixture CO2-N2-He under pumping by e-beam initiated discharge. The electron beam was formed in a gas diode filled the same gas mixture.
The calculation of charged particles densities in gas flow discharge chambers
Rafail K. Safioulline, K. R. Safioulline
Glow discharge in a gas flow is widely used for the creation of active mediums for powerful molecular gas lasers. In this paper transverse glow discharge chambers in electronegative gas flow were investigated numerically by alternating direction method. A case of continuous anode and partitioned cathode was considered. The rates of ionization and of electron attachment were received by means of the electron energy distribution function (EEDF) calculation. As a result, two-dimensional distributions of charged particles and of electric potential inside such chambers were obtained.
Numerical simulation of the processes in fast flow gas discharge CO2 lasers
Ravil S. Galeev, Rafail K. Safioulline
In the report the results of numerical simulation of the processes in discharge chambers (DC) of fast flow CO2 lasers, are presented. The investigations for longitudinal glow discharge (quasi-one-dimensional and two-dimensional flow) using four- and six-temperature models, were performed. Distributions of gas dynamic quantities, densities of charged particles, electric field strength, as well as vibrational temperatures of CO2, N2 and CO species, within the DC were calculated. Quasi-one-dimensional consideration of processes for powerful CO2 lasers with conic discharge tubes has shown that narrowed along the gas flow tubes must be more effective for laser operation than cylindrical ones. The calculated quantities are in satisfactory agreement with available experimental data.
Effective electron impact excitation cross-sections of SrI singlet levels
Anatoly N. Soldatov, L. V. Gorchakov, A. V. Stebeneva
Kinetic calculations of the active medium of a Sr-vapor laser require knowledge of effective cross sections of the processes developing in a discharge plasma. We have calculated effective electron-impact excitation cross sections of SrI singlet levels using the Born approximation. The calculations were performed for the incoming electron energy lying in the range between the excitation threshold and 600 eV. The results obtained were compared with experimental and theoretical data known from the literature. The closest agreement was observed for the excitation cross section of the resonance 5p 1P01 level (upper laser level for lasing at λ=6.45 µm). A number of the calculated effective cross sections for excitation of high-lying states are presented.
Laser Systems and Applications
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Photoconductive response of type IIa diamond in the 222-353-nm range
Mahadevan Krishnan, Evgenii E. I. Lipatov, D. Parks, et al.
Diamond radiation detectors (DRDs) operate on the principle of photoconductive response of the normally insulating, Type IIa diamond when dosed by electromagnetic radiation or high energy particles. As detectors, they offer fast response (~100 ps) and can handle high radiation doses (~1 GGy) without degradation. Diamond also offers significant advantages over semiconducting materials as a compact, bi-polar, high voltage switching medium because of its high dielectric strength and thermal conductivity. However, the wide band-gap of diamond and its normally insulating state impose stringent requirements on the trigger radiation that is used to make the diamond conductive. This paper describes a simple model for conduction in diamond, and compares this model with experimental conductivity as measured in a natural diamond Type IIa radiation detector that was irradiated by laser excitation at various wavelengths from 222-353 nm. The DRD geometry consisted of a 3x1x0.5 mm3 Type IIa diamond with metallization on the 3x0.5mm2 sides. The DRD was exposed to laser light in the orthogonal 3x1 mm2 plane. Agreement with the measured data is achieved by fitting a parameter (defined here as β) at the various irradiation wavelengths. This fitting parameter is itself a function of two physical quantities: α, the absorption coefficient of the diamond and εo, the ionization cost to produce a hole-pair. Using published values of α, we deduce values of εo and compare them with published values for Type IIa diamond in the deep UV to soft x-ray regions. This model also provides a basis for design of high voltage diamond switches that are triggered by near-bandgap (220-250 nm) UV radiation.
Modification of thin metal and ceramic films by UV and IR laser radiation
Investigation of the modes of thin metal and ceramic films (0,3-1 μm) removal from the glass and stainless steel substrate by IR and UV laser radiation has been performed. It is presented that the efficient film destruction and removal occurs due to laser induced thermal strength under laser fluxes of ~0.5 J/cm2 not sufficient for phase transformation.
Effect of plasma needle on cultured cells
I. E. Kieft, N. A. Dvinskikh, Jos L. V. Broers, et al.
To investigate a possible application of plasma in fine surgery, we studied the effects of a small atmospheric glow discharge on living cultured cells. The plasma source used for this purpose was the "plasma needle". Plasma needle is a small (below 1mm) non-thermal radio-frequency glow, operating in helium mixtures with air at ambient pressure. Plasma treatment of cultured cells resulted in detachment of the cells. Viability tests using propidium iodide staining in combination with confocal laser scanning microscopy confirmed that detached cells as well as surrounding cells remained alive. When the cells received a low dose of plasma treatment, they reattached within a few hours to the surface of the culture flask and to each other. Removal of cells with high precision, without damage to adjacent cells, promises to become a new surgical technique. For investigation of the mechanism causing this detachment we investigated the gas mixture of the plasma with Raman scattering measurements. Radicals diffusing from the plasma into a liquid were detected by means of fluorescent probe in combination with laser-induced fluorescence spectroscopy.
A sealed-off strontium vapor laser
Anatoly N. Soldatov, Alexander G. Filonov, Alexei S. Shumeiko, et al.
A sealed-off strontium-vapor laser for medical applications is examined. This is an integrated system that accommodates an excitation circuit, a laser cavity, and an active element. The active medium is excited by means of a modified Blumlein circuit. An unstable resonator of the telescopic type allows a near-diffraction-limited laser beam to be generated. Lasing is obtained in atomic strontium lines at λ=2.06, 2.2, 2.69, 2.92, 3.011, and 6.45 μm and in ionic strontium lines at λ=1.033 and 1.091 μm. We have studied experimentally the behavior of spectral distribution of the output power at varying power delivered to the discharge. It is found that 95% of laser radiation is concentrated in the line at λ=6.456 μm, which corresponds to a lasing power of ~ 2.5 W. Moreover, the time characteristics of lasing pulses are investigated. The radial inhomogeneity of the laser beam is examined. We have conducted lifetime testing of Sr-vapor active elements. The average output power exhibits a modest decrease (5%) within 300 h of a continuous operation. Notably, the pumping characteristics remain unchanged.
A comparative evaluation of efficiency of different methods of treating pretumoral changes of bronchial epithelium by clinical-immunological data
O. V. Cheremisina, E. L. Choinzonov, V. A. Evtushenko, et al.
No Abstract Available
Influence of nitric oxide on antitumor activity of photodynamic therapy: laser systems for PDT
V. A. Evtushenko, G. V. Zagrebelnaya, Anatoly N. Soldatov, et al.
Photodynamic therapy (PDT) is a promising therapeutic modality used for the cancer treatment. The principle of PDT is based on the formation of singlet oxygen and other activated oxygen metabolites that result in apoptotic tumor cell death. However, the resistance of some tumors to radiation therapy is recorded. The search for the chemical agents, therefore, which are able to enhance the antitumor activity of radiation therapy and induce the tumor cell apoptosis is of great importance. The use of pharmacologic agents such as donors of nitric oxide (NO) or modulators of NO-synthase may be one of the approaches to improve the therapeutic efficiency of PDT. The aim of our study was to evaluate the feasibility of using nitric oxide in combination with PDT for enhancing the induction of tumor cell apoptosis.
Incoherent UV and VUV Sources and Laser Output Conversion
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Excimer lamps: history, discharge physics, and industrial applications
Ulrich Kogelschatz
The development of modern excimer lamps (excilamps) is reviewed. These lamps provide high intensity ultraviolet (UV) of vacuum ultraviolet (VUV) radiation generated by decaying excimer complexes formed in various non-equilibrium discharges. Due to the absence of self-absorption in the plasma this process can be highly efficient and tolerates high power loadings. With different fill gases narrow-band radiation at various UV and VUV wavelengths can be obtained. Phosphor coatings can be used to obtain visible radiation. Cylindrical as well as flat planar configurations are used to provide high photon fluxes over large areas. The special characteristics of excimer lamps led to a number of novel applications for low-temperature materials processing (oxidation, deposition, annealing, etching, cleaning, micro-structuring) and to applications in photochemical purification of air and water using advanced oxidation processes (AOPs) based on O2 and H2O photolysis. Further applications are expected in analytical instrumentation.
Electron-beam-pumped ultraviolet light sources
Jochen Wieser, Andrei Morozov, Fabian Muehlberger, et al.
Low energy electron beam excitation of dense gases is used for developing UV and VUV light sources. Emission spectra for various gases are shown and a first application for single photoionization in a time of flight mass spectrometer is presented.
The VUV dimer spectra excited in condensed krypton
Gennady N. Gerasimov, Boris E. Krylov, Reinhold Hallin
The vacuum ultraviolet (VUV) emission spectra of krypton homonuclear molecules (dimers) were observed in the wavelength range 120-200 nm. The krypton dimers were excited in a DC capillary discharge and the wall of tube could be cooled with liquid nitrogen. The homogeneous DC discharge was a straight channel in the middle of capillary tube. The gas krypton pressure in the discharge channel could be stabilized in the pressure range from 3 hPa to 1000 hPa. The DC discharge current density and the electron concentration were ~ 10 A/cm2 and ~ 2-4 1014 cm-3, respectively. The VUV krypton spectra excited in vicinity of solid krypton were compared with the spectra recorded without condensed krypton. The VUV spectral lines intensities were observed as nonlinear function of the discharge length. This nonlinear increase of intensity with the length of the tube has still to be explained.
Compact XUV excimer radiation sources and their application
Andrei V. Fedenev, Andrei Morozov, Jochen Wieser, et al.
Low energy electron beam excitation of dense helium and neon was used for light production in the extreme ultraviolet (XUV) wavelength range. The entire system was completely filled with the working gas avoiding the use of vacuum equipment for light production, propagation and detection. Emission spectra from He and Ne are dominated by the second continua with peak intensities at 80 and 83 nm, respectively. The hydrogen Lyman-α line was observed as the dominant impurity line. This XUV light source was used for transmission measurements of LiF near its absorption edge.
Modeling of barrier filaments as miniglow discharge: Xe2 (172 nm) and XeCl (308 nm) excilamps
A. M. Boichenko, Mikhail I. Lomaev, Victor F. Tarasenko, et al.
The modeling of Xe2 and XeCl excilamps with glow discharge pumping is performed. The comparison with available experimental data is done. The modeling is connected with possibility of description of barrier discharge filaments by glow discharges.
New bactericidal UV light sources: excilamps
Edward A. Sosnin, Larisa V. Lavrent'eva, Mikhail V. Erofeev, et al.
A reliable bactericidal effect on Escherichia coli cells irradiation by excilamps has been established. Both on primary and secondary irradiation there exists the reciprocally proportional dependence between irradiation doze (or exposure time) and survived cells number. The microorganisms survived after primary irradiation are shown to have not changed sensitivity to excilamps irradiation. The best results have been obtained during XeBr-excilamp irradiation. Owing to their technical parameters, the excilamps are promising systems for UV-sterilization. Comparison of capacitive discharge excilamp characteristics with other conventional UV light sources in presented. A comparative study on UV doze effect of a barrier discharge KrCl-excilamp (λ = 222 nm) on Staphylococcus aureus and Escherichia coli inactivation was carried out. KrCl-excilamp emission power is 65 W, and emitting area is 0.1 m2. It has been demonstrated that Staphylococcus aureus cell sensitivity to UV radiation at this wavelength is higher than that of Escherichia coli.
Biological objects pretreatment optimization using XeBr excilamps for mercury concentration control by ASVA method
Valentina N. Batalova, Oksana A. Bylatskaya, Edward A. Sosnin
Simplified pretreatment of biological objects united chemical (HNO3+H2O2) and further photochemical sample oxidation has been suggested. Optimization of conditions was performed using the method of fractional factorial design of experiments. Availability of excimer gas discharge excilamp based on working molecule XeBr* has been shown as an alternative to mercury quartz at pretreatment of biological objects of complex organics. The XeBr-excilamp is remarkable by its long lifetime and operation reliability.
Study of photocatalytic effect of narrow band irradiation at 206 and 282 nm on oil in aqueous solution using TiO2
Yuri P. Meshalkin, Elena S. Samoilova, Edward A. Sosnin, et al.
Kinetics of oil water solutions photodegradation under action of narrow band irradiation of XeBr*-excilamp (λ~283 nm) and iodine lamp (λ~206 nm) is presented. Power of lamps reached 10 mW/cm2. In all experiments TiO2 (rutile) powder was used as a catalytic agent. Photocatalytic degradation kinetics was controlled by laser fluorescence spectrometer. The measuring complex was based on the pulse-repetitive Nd:YAG laser (266 nm) with Q-switching. Dependencies of fluorescence intensity on irradiation time were made using laser-induced fluorescence spectra. It has been found that at initial time of irradiation, the photodegradation rate in oil aqueous solutions was higher in the case of XeBr* lamp, however, after 20 minutes of irradiation, major photodegradation was observed in the both cases.
Small-sized KrCl, XeCl, and XeBr excilamps
Mikhail V. Erofeev, N. L. Medvedev, Edward A. Sosnin, et al.
Simple configuration small-sized KrCl-, XeBr- and XeCl-excilamps based on near-surface capacitive discharge are offered. The devices are demonstrated to possess high specific energy characteristics (radiation power density of up to 10 mW/cm2), permanently small radiation volume, as well as narrow radiation band. Operating lifetime of a sealed-off excilamp is above 1000 hrs.
Spontaneous UV source based on pulsed discharge in Xe (Kr, Ar)
Mikhail I. Lomaev, D. V. Rybka, Victor F. Tarasenko, et al.
This paper reports on experimental results obtained during study of the source of UV spontaneous radiation based on high-current pulsed discharge in xenon and krypton being developed for the purposes of influence upon diamond detector. It has been shown that xenon lines have the highest emission spectral density in the UV range of discharge. The energy share of radiation in the range 200-250 nm with respect to the complete radiation energy in the whole control band 200-650 nm versus excitation pulse duration reaches 30-50%. Maximal density of radiation power above 50 kW/cm2 in UV range has been registered under xenon pressure of 550-650 Torr. Changing xenon for krypton (argon) lead to double decrease of emission energy. Minimal resistance of 1×3 mm2 irradiated diamond crystal, registered at the moment of current maximum in diamond detector circuit is 300.Ω.