The results of experimental studies of various generation modes of runaway electron beams (RAEBs) are presented. The main attention is paid to the mode when the RAEB with the highest amplitude are generated in air at atmospheric pressure. Other modes are discussed too: the most implemented and often mentioned by other authors generation mode as well as the mode when RAEB is generated after breakdown.
Our study describes effective techniques to transfer heat away from UV emitters based on dielectric barrier discharge excilamps. It presents findings from an investigation into the efficiency of excilamp radiation when cooled by air, inert gas, and liquid refrigerants. The devised cooling techniques were used to create radiation sources with a UV power density of up to 117 mW / cm2.
Cumulation effect of a beam of runaway electrons formed in a high-voltage nanosecond discharge in air at pressures of 3-105 Pa and discharge gap length d of 1 - 5 mm was studied. Optimal conditions of the effect in discharge gap with a tubular potential cathode and grounded flat anode was achieved at an air pressure of ~ 5 Pa and d of 2.7 mm. An electron beam current pulse was recorded behind a foil anode with high (up to ~ 80 ps) time resolution. It was found that, due to the cumulation effect, a through hole is formed in an aluminum foil 20 μm thick after 2-3 discharge pulses. The electron beam was found to register around the zone of maximum beam current density as well. As follows
The possibility of using method for measuring the absorbed energy by means of a shunt current was considered. Experimental results of such measurements in a plasma of pulsed electric discharges excited by nanosecond voltage pulses, which are applied to a nonlinear load through long transmission line, are presented. A comparison was made with the technique of measuring the absorbed energy by means of a voltage divider and a shunt current located directly in the load.
VUV radiation of run-away electron preionized discharge (REP DD) in different gas mixtures is studied. Efficient lasing was achieved on ArF* (193 nm) and F2* (157 nm) molecules. Narrowband VUV radiation (near 147 nm), corresponding to the optical transition of a heteronuclear dimer ArXe*, was recorded from the REP DD plasma in (He)-Ar-Xe mixture. Amplifying properties of the discharge plasma related to this radiation were found.
Laser action in run-away electron preionized discharge (REP DD) was studied. Efficient laser emission was obtained in wide spectral range from IR to VUV. It was shown that ultimate efficiency of non-chain chemical lasers on HF (DF) molecules and N2 laser at 337.1 nm can be achieved in REP DD. New mode of N2 laser operation with 2 or 3 peaks in successive REP DD current oscillations was found. Efficient lasing on KrF* and XeF* excimer molecules with parameter close to laser parameters of lasers pumped by conventional transverse discharge were demonstrated for the first time. Laser action on F2* at 157 nm and rare gas fluorides under REP DD pumping was obtained for the first time, as well. The efficiency and pulse duration of VUV F2* laser under REP DD excitation are comparable with those obtained in transverse discharges with preionization. VUV emission of REP DD in binary and ternary Ar-Xe-(He) and Ar-Kr-(He) mixtures at wavelength close to 147 nm was measured. Possibility of VUV lasing in mixtures of rare gases is considered.
Formation features of run-away electron preionized diffuse discharge (REP DD) and REP DD properties in different experimental conditions are studied. It was shown that sufficient uniformity of REP DD allows its application as an excitation source of lasers on different gas mixtures at elevated pressure. Promising results of REP DD application for development of gas lasers are shown. Stimulated radiation in the IR, visible and UV spectral ranges was obtained in the diffuse discharge. Ultimate efficiency of non-chain HF(DF) chemical and nitrogen lasers on mixtures of SF6 with H2(D2) and N2 was achieved. New operation mode of nitrogen laser is demonstrated under REP DD excitation. Kinetic model of the REP DD in mixtures of nitrogen with SF6 is developed allowing to predict the radiation parameters of nitrogen laser at λ = 337,1 nm. Long-pulse operation of rare gas halide lasers was achieved.
Main parameters of plasma formed during the pulse and pulse-periodic runaway electron preionized diffuse discharge (REP DD) in argon, nitrogen and air at high pressure were measured. An electron concentration in the plasma of pulse and pulse-periodic REP DD in the elevated pressure argon was determined. Average for pulse value of electron density in the argon plasma of pulse REP DD was ~ 3·1015 cm-3. Dynamics of electron density in the atmospheric-pressure plasma of the argon during the REP DD was determined. Measured average values of an electron concentration in the plasma of the pulse-periodic REP DD in atmospheric-pressure air and nitrogen were ~ 3·1014 and ~ 4·1014 cm-3, respectively. In addition, for the plasma formed during the pulse-periodic REP DD in atmospheric-pressure nitrogen and air average values of an electron temperature and reduced electric field, as well their dynamics were determined. Average value of an electron temperature during the pulse duration for nitrogen and air plasmas was ~ 2 eV. Dynamics of an electron temperature and reduced electric field strength was registered. Data on rotational and gas temperatures in the discharge plasma of atmospheric-pressure nitrogen formed in pulse (Tr ≈ 350 K, Tg ≈ 380 K) and pulse-periodic (Tr ≈ 750 K, Tg ≈ 820 K) modes were obtained. In addition, measured value of vibrational temperature in REP DD’s plasma formed in pulse mode in nitrogen at pressure of 1 bar was Tv ≈ 3000 K.
It was shown that run-away electron preionized volume (diffuse) discharge (REP DD) can be used as an excitation source of gas mixtures at elevated pressures and can produce laser emission. We report experimental and simulated results of application of the REP DD for excitation of different active gas mixtures. Kinetic model of the REP DD in mixtures of nitrogen with SF6 is developed allowing predicting the radiation parameters of nitrogen laser at 337.1 nm. Peculiarities of the REP DD development in different gas mixtures are studied, as well. It was shown that the REP DD allows obtaining efficient lasing stimulated radiation in the IR, visible and UV spectral ranges. New operation mode of nitrogen laser is demonstrated under REP DD excitation. Laser action on N2, HF, and DF molecules was obtained with the efficiency close to the limiting value. Promising prospects of REP DD employment for exciting a series of gas lasers was demonstrated. It was established that the REP DD is most efficient for pumping lasers with the mixtures comprising electro-negative gases.
It was shown that run-away electron preionized volume (diffuse) discharge (REP DD) can be used as an excitation source of active gas mixtures at elevated pressures and can produce laser emission. We report experimental and calculated results of application of the REP DD for excitation of different active gas mixtures. It was shown that the REP DD allows to obtain efficient lasing stimulated radiation in the IR, visible and UV spectral ranges. Kinetic model of the REP DD in mixtures of nitrogen with SF6 is developed allowing to predict the radiation parameters of nitrogen laser at 337.1 nm. Promising prospects of REP DD employment for exciting a series of gas lasers was demonstrated. Lasing was obtained on molecules N2, HF, and DF with the efficiency close to the limiting value. It was established that the REP DD is most efficient for pumping lasers with the mixtures comprising electro-negative gases.
Breakdown of the gaps with a non-uniform electric field filled with nitrogen and air as well as with other gases under
high-voltage nanosecond pulses was investigated. It is shown that conditions of obtaining a diffuse discharge without a
source of additional ionization are extended at the voltage pulse duration decreasing. A volume discharge is formed due
to the gap pre-ionization by runaway electrons and X-ray quanta. At a negative polarity of the electrode with a small
radius of curvature, a volume (diffuse) discharge formation is determined by pre-ionization with runaway electrons
which are generated due to the electric field amplification near the cathode and in the gap. At a positive polarity of the
electrode with a small radius of curvature, the X-ray radiation, generated at the runaway electrons braking at the anode
and in the gap, is of great importance in a volume discharge formation. A runaway electrons preionized diffuse discharge
(REP DD) has two characteristic stages. In the first stage, the ionization wave overlaps the gap during a fraction of a
second. The discharge current is determined by the conductivity current in the dense plasma of the ionization wave and
the displacement current in the remaining part of the gap. The second stage of the discharge can be related to the
anomalous glow discharge with a high specific input power. During the second stage, the gap voltage decreases and the
cathode spots formed as a result of explosive electron emission can participate in the electron emission from the cathode.
At the increase of the voltage pulse duration and specific input power, the REP DD transforms into a spark discharge
form. A REP DD is easily realized in various gases and at different pressures; see [1] and references in [1]. At pressure
decrease was obtained the anode electrons beam current to rise (up to ~2 kA/cm2 in helium). At the REP DD, the anode
is influenced by the plasma of a dense nanosecond discharge with the specific input power up to hundreds of megawatt
per a cubic centimeter, by the electrons beam, shock wave and optical radiation from discharge plasma of various
spectral ranges, including UV and VUV. This allows forecasting the REP DD application for modification and cleaning
of metal and dielectric surfaces. The REP DD is promising as well for creation of the VUV-range excilamps with a high
radiation power in a pulse. REP DD was use for pumping different gas lasers.
A windowless excilamp, a xenon excilamp with the high specific power of radiation and an air-cooling KrCl excilamp
for microelectronic applications are described. The excilamps have the total radiating surface up to 900 cm2. The VUV
specific average power of a windowless excilamp is 3 mW/cm2 and 5 mW/cm2 for argon (λ ~ 126 nm) and krypton (λ~146 nm) accordingly at distance of 3 cm from the emitting surface. The xenon excilamp (λ ~ 172 nm) has 50 W of the average total VUV power and 120 mW/cm2 of density and the
large-aperture air-cooling KrCl (λ ~222 nm) excilamp has
30 mW/cm2 of the radiation density and the radiation homogeneity 12 %.
Emission characteristics of a nanosecond discharge in nitrogen, inert gases and its halogenides without preionization of
the gap from an auxiliary source have been investigated. A volume discharge, initiated by an avalanche electron beam
(VDIAEB) was realized at pressures up to 12 atm. It has been shown that at VDIAEB excitation no less than 90%
energy in the 120-850 nm range is emitted by Xe, Kr, Ar dimers. Xenon spectra in the range 120-850 nm and time-amplitude
characteristics have been recorded and analyzed for various excitation regimes. In xenon at pressure of 1.2
atm, the energy of spontaneous radiation in the full solid angle was ~ 45 mJ/cm3, and the FWHM of a radiation pulse
was ~ 110 ns. The spontaneous radiation power rise in xenon was observed at pressures up to 12 atm. Pulsed power
densities of radiation of inert gases halogenides excited by VDIAEB was ~ 4.5 kW/cm2 at efficiency up to 5.5 %.
Spectral, energy and temporal parameters of a pulsed discharge in xenon are studied. It is shown that the use of unidirectional current pulse instead of oscillating one improves radiation power in the range 200-350 nm, while duration of the radiation pulse at half-maximum decreases. The use of SOS-diodes in the pulse generator allows obtaining the maximal radiant intensity 64 kW/sr in the range 200-350 nm and the pulse duration of ~2 μs FWHM.
Experimental time-amplitude and spectral characteristics of emission from B-X transitions of Xe*2 (λ = 172 nm), Kr*2 (λ = 146nm), and Ar*2 (λ = 126 nm) molecules excited by a dielectric barrier bounded pulsed corona discharge are presented as function of gas pressure, pulse repetition rate and average excitation power. In optimal experimental conditions emission efficiency of Xe and Kr dimers is 45-50% and 25-28%, respectively.
This paper describes the development of an intense xenon gas discharge UV flash-lamp. The emission of the flash-lamp is tailored to serve as a trigger for high voltage and current, photoconductive diamond switches. Xenon flash-lamps are broadly used for many applications, but have not been optimized at high currents (~10 kA), for short durations (<1 μs), and with emphasis on the UV spectral band of 220-250 nm. The diamond photoconductive switch requires trigger UV radiation in this band because it results in bulk and efficient absorption. We present the results of our flashlamp optimization, tailored for UV switching requirements of CVD diamond. The study's emphasis was on small diameter (≤10 mm), short A-K gap (0.5-5mm) xenon gas discharge lamps. Input electrical power on the order of 25MW was typical. Emission power, spectral energy distribution and their associated lamp efficiencies are presented. The optimization studies included variation of A-K gap, fill pressure, and driver current waveform, based on the dominant physics of the expansion of the gas discharge during sub-microsecond operation. Diamond response to UV exposure from xenon gas discharge lamps, in terms of bulk induced photoconductivity and induced charge carriers is discussed.
The studies devoted to free-expanding and bounded discharges, taking place in a Xe flashlamp, have been carried out. With such a discharge bounded by the walls of a bulb the maximal UV radiation power density was ~ 700 kW/cm2 on the internal surface ofthe bulb and ~ 380 kW/cm2 on its external surface.
Efficient radiation of Xe2*, KrBr*, KrCl*, XeI*, Cl2, XeBr*, XeCl* molecules and Iodine atoms was obtained. Some types of UV and VUV excilamps with different discharge geometry excited by capacitive discharge, barrier discharge and glow discharge are presented.
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.
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.
A discharge in high-pressure xenon excilamps is studied experimentally and theoretically. In the absence of an additional source of xenon preionization, the volume discharge is produced in the form of a diffuse cloud or diffuse cones at pressures of several hundreds of torrs. Under these conditions, radiation is emitted with a high efficiency within the VUV spectral range. The results of simulations have shown that, at the pressure on the order of 100 Torr and the field voltage on the order of 10 kV/cm, the established near-cathode layer is on the order of several tens of microns, which is much less than the wire radius. The cathode layer, the potential drop in the near-cathode area is much lower than the voltage applied to the discharge gap. We put forward a hypothesis that the formation of the volume discharge is due to the presence of dense plasma in the near-cathode area, and this plasma plays the role of a plasma cathode.
Experimental results obtained in study of spontaneous UV radiation source based on high-current pulsed discharge in xenon developed for irradiation of diamond crystal to convert it into conductive state are presented. It is shown that at the pressure of about 450 Torr radiation of Xe lines predominate in UV range of discharge radiation spectrum. The part of radiation energy in the range of 200 - 250 nm with respect to the radiation energy of the whole range recorded (200 - 650 nm) may reach 50%. The maximum density of radiation power was 185 kW/cm2. At pressure increasing up to 1200 Torr, the part of thermal radiation increases too. In this case the part of radiation energy in the range of 200 - 250 nm does not exceed 20%.
At present time, excilamps excited by a barrier discharge are the simplest and perspective as the sources of UV and VUV radiation. Much research is devoted to such excilamps. Traditionally, sinusoidal oscillators are used as excitation sources. The present work devoted to study the impact of excitation pulse form and other conditions on efficiency of a barrier KrCl and XeCl excilamps. The main results of the work performed are the following. The most high specific radiation power values were obtained at the excitation at the excilamp by voltage pulses of different polarity at maximum pulsed repetition rate (p.r.r) of 100 kHz, and made depending on operating conditions of excilamp, up to 120 mW/cm3. From the oscilloscope traces of voltage pulses, current and radiation it is seen that radiation is being registered within the whole current pulse duration. The most high values of average radiation power and efficiency were achieved, correspondingly, 100 W and 13%. Influence of pulse repetition rate of excitation of different temporal mode on the type of formed discharge, as well as efficiency and output parameters of Xe-Cl2 barrier discharge excilamp were studied. It has been found that at pulsed repetition rate of about 1 kHz and higher there are brightly glowing microdischarges - filaments observed in the discharge plasma. With this, the efficiency of excilamp practically keeps unchanged in the frequency range <EQ 1 kHz and monotonously decays either at further increase of excitation p.r.r. or at excitation power increase for the fixed frequency of excitation pulses.
In the present paper, Iodine XeI*, XeCl*, KrCl barrier, glow and capacitive discharge excilamps have been studied. Xe-I2 or Xe-He-I2 excilamps emit at iodine monatomic resonance lines in the range of 180-210 nm, and on XeI molecule band. Besides that, by varying pressure and mixture composition, it is possible to control relation between iodine monatomic lines and XeI* molecule band radiation intensity. The efficiency level is up to 12 percent. The lifetime in sealed-off excilamps was more 1000 h. It is shown that at barrier KrCl and XeCl excilamps excitation by short unipolar or bipolar voltage pulse the efficiency is higher than by sine pulses excitation. Output at (lambda) approximately 222 nm up to 100 W and at 308 nm up to 75 W from barrier discharge excilamps was obtained. Presence of filaments occurs to be a necessary condition to obtain high efficiency since in that case a demanded level of excitation specific power is being achieved. Radiation pulse delay relatively to excitation in the conditions of homogeneous discharge probably demonstrates low efficiency of KrCl* and XeCl* molecules formation at a low level of excitation power. Output at (lambda) approximately 222 nm up to 190 W and at 308 nm up to 91 W from glow discharge excilamps was demonstrated.
The paper is devoted to experimental study of discharge and radiation characteristics taking place in Xe one-barrier excilamps at broad variations of excitation pulse parameters and gas fill-pressures. The B-X band of the molecule Xe2* dominates the lamp spectrum and has high efficiency. Radiation of monatomic lines and luminescence of the lamp bulb can be observed too. The molecule Xe2* band B-X radiation of luminescence time dependence and luminescence of the lamp bulb quartz are similar, at the same time the radiation of Xe monatomic line (lambda) equals 467 nm has obviously some other form. Depending on excitation conditions, i.e. power, duration and excitation impulse form, a gas discharge Xe excilamp, different by homogeneity level and radiation efficiency types of discharge can be realized. Formation of discharge homogeneity is the necessary condition to obtain high efficiencies of excimer radiation in this type of lamp. In one-barrier xenon excilamps with internal small curvature of an electrode, a homogeneous discharge forms at pressures up to 300 Torr.
In the present paper, Xe-I2 and He-I2 glow and capacitive discharge excilamps have been studied. These excilamps emit at iodine monatomic resonance lines in the range of 180 - 210 nm, and on XeI* molecule band ((lambda) max equals 253 nm). Besides that, by varying pressure and mixture composition, it is possible to control relation between iodine monatomic lines and XeI* molecule band radiation intensity. The efficiency level is up to 10%. The lifetime in sealed-off and quasi-sealed-off modes is up to 1000 h.
In this paper, the calculations on decay of voltage, power and excitation energy in barrier discharge excilamps is presented. In order to verify these parameters calculations, measurements on energy input into the gas discharge plasma both using common techniques (calorimeter and volt-coulomb discharge characteristics of discharge) and integration of calculated excitation power were done. The obtained results are in good agreement that points to correct calculations done on necessary excitation parameters in the barrier discharge excilamps.
Excitation pulse form and power and some other discharge parameters influence on barrier discharge KrC1 excilamp efficiency was studied in present paper. It is shown that at barrier KrC1 excilamp excitation by short (2÷2,5 µs) unipolar or bipolar voltage pulses the efficiency is higher than by sine pulses excitation. Presence of filaments occurs to be a necessary condition to obtain high efficiency since in that case a demanded level of excitation specific power is being achieved. Radiation pulse delay relatively to excitation in the conditions of homogeneous discharge probably demonstrates low efficiency of KrCl* molecules formation at a low level of excitation power.
Power characteristics of four excilamps with short-pulse duration discharge plasma radiation have been investigated experimentally. At mixture pressure of 30 Torr the radiation pulse power density has made at (lambda) approximately 222 nm 0.2 kW/cm2, 0.15 kW/cm2, 0.09 kW/cm2 for I-, H- and L-type excilamps, respectively. The maximal radiation pulse power density was received for modernized I-type excilamp and it has made 0.3 kW/cm2. It has been revealed that pulse radiation output is mostly determined by excilamp voltage value, discharge geometry, value of peaking capacitance, and gas medium density.
The possibility of creation of capacitive discharge excilamps with short pulse duration was studied. There were three types of pulsed excilamps in experiments: cylindrical glow discharge lamp, capacitive discharge lamp, high pressure volume discharge planar lamp with UV-preionization of discharge gap. In capacitive discharge cylindrical KrCl-excilamp, at (lambda) approximately 222 nm the radiation pulse power through the end face of a lamp up to 2.5 kW has been obtained. Powerful radiation pulses of 50 ns in duration were obtained at pulse repetition rate of 1 kHz. In case of high pressure volume discharge at operating pressure of several atmospheres the radiation peak power density values were as much as 5 kW/cm2 at (lambda) approximately 250 nm, and 3.5 kW/cm2 at (lambda) approximately 222 nm and at (lambda) approximately 308 nm. In cylindrical longitudinal excilamp with inner electrodes with Xe- I2 mixture the total pulse power of 75 kW has been obtained. The first experiments with harnessing of inductive energy stores for excilamp excitation have been carried out.
Investigation was made ofthe characteristics ofXeCl (λ ~ 308 nm), KrC1 (λ ~ 222 nm) and Xci (λ ~ 253 nm) capacitive discharge excilamps. High efficiency of exciplex molecules and simple design have been obtained under capacitive HF discharge excitation. Cylindrical excilamps with radiation output through side surface ofthe cylinder and through one or two windows placed on the tube ends have been developed. High UV radiation power and electrical power deposition to fluorescence conversion resulted in efficiencies of up
to 12%. The study of XeC1, KrCl and XeI excilamps have shown, that it is possible to create sealed-off samples with lifetime more than 1000 hours. The stability of output parameters ofthe capacitive discharge excilamps is studied and the mechanism of chlorine losses in low pressure halogencontaimng excilamps made of quartz was determined.
The possibility of creation of capacitive discharge excilamps with short pulse duration was studied. In capacitive discharge cylindrical KrClexcilamp, at λ~222 nm the radiation pulse power up to 2.5 kW was obtained. Powerful radiation pulses 50 ns in duration were obtained at pulse repetition rate of 1 kHz.
The results of experimental study of Ne emission in the wavelength range of 200 - 600 nm under excitation by electric discharge and short-duration e-beam are presented. It was found that temporary behavior of the emission intensity distinguished in different spectral regions. The nature of the radiation in the ranges of 120 - 300 nm and of 300 - 500 nm was suggested due to transitions of molecular ions and those from Rydberg states Ne2R, respectively.
Operating parameters of powerful excilamps with different discharge geometry pumped by glow discharges, high-pressure volume discharge with UV-preionization and barrier discharge are presented. Intense radiation of Ar2*, Kr2*, Xe2*, ArF*, KrBr*, Cl2, KrCl*, KrF*, XeI*, XeBr*, XeCl*, XeF*, I2 and IBR molecules was obtained in rare gas or in rare gas -- F2 (CH3Br, Cl2, HCl, I2, NF3) mixtures. Excilamps with high spatial uniformity of the output, narrow emission line and high gas life-time were developed. It was shown that efficiency of luminescence of exciplex molecules KrCl* of about 30% can be obtained in high- voltage glow discharge and positive column of glow discharge. Output at (lambda) approximately 222 and 308 nm up to 200 W from single excilamp and 500 W from three excilamps operating in parallel was demonstrated. It was shown that the efficiency of barrier discharge excilamps pumped by sinusoidal pulses several tens microseconds in duration can be sufficiently improved.
Excilamps with different tube geometry pumped by continuous glow and barrier discharges are described. It was shown that the efficiency of barrier discharge excilamps pumped by sinusoidal pulses with duration of several tens microseconds can be sufficiently improved. The range of UV wavelength emitted by glow discharge excilamps was extended. Intense radiation of KrBr*, XeBr*, I2* and IBr* molecules was obtained in rare gas - CH3Br (I2) mixtures pumped by glow discharge KrCl* excilamp ((lambda) approximately 222 nm) with output power up to 200 W was developed. UV power of 500 W from three KrCl* excilamps operating in parallel was demonstrated. Efficiency of exciplex molecule luminescence in the positive column of glow discharge was found to be as high as approximately 30%.
The present report describes gas lasers pumped by generators with inductive energy storage and semiconducting opening switch. It is shown that these generators significantly improves output parameters of different gas lasers. Longitudinal small-scale N2 laser and CO2 and non- chain HF transverse discharge lasers are developed using this pumping technique. Efficiencies of CO2 and HF lasers up to 17% and 5,5%, respectively, were demonstrated. Advantages of generators with inductive energy storage are discussed.
Novel single block process facility including UV excilamp and sources of atomic hydrogen is described. Circular sealed-off KrCl* excilamp emitting two intensive bands at 195 and 222 nm was used. The source of atomic hydrogen on the base of reflecting Penning arc discharge was placed in line with the lamp. Semiconducting structures were treated in an expanding effusion jet of atomic hydrogen. The possibility to realize the process of cleaning GaAs surface under joint action of atomic hydrogen and UV radiation has been investigated. Effect of UV radiation on the rate of removing oxide layer is found at low temperature (18 - 100 degree(s)C). The mechanism providing an explanation for this event is suggested. The possibility to realize GaAs surface cleaning using successive performing the procedures of the surface treatment by atomic hydrogen, its oxidation with UV- stimulation and additional treatment by atomic hydrogen was also studied. The sources of atomic hydrogen and UV radiation developed allows to improve cleaning control and provides a way of producing the surface with specified properties.
KEYWORDS: Hydrogen fluoride lasers, Energy efficiency, Pulsed laser operation, Laser energy, Electron beams, Chemical lasers, Switches, Chemical reactions, Diodes, Argon
Non-chain HF lasers initiated by electric discharge and e- beam are described. A generator with an inductive energy storage and semiconducting opening switch was used for discharge formation. The generator was shown to be very promising for development of efficient discharge HF lasers with high output energy. It produces very uniform discharge in SF6-H2(C3H8) gas mixtures at elevated pressure and increases its stability. Discharge HF laser efficiency up to 5.5% was demonstrated. Radially convergent e-beam was used to pump 30 1 HF laser. Optimal gas mixture SF6:H2 equals 8:1 under pressure of 0.45 atm was chosen to provide no more than two-fold specific output power variations across the laser beam area. Output energy as high as 115 J and efficiency with respect to e-beam energy deposited into gas mixture up to 7-8% were demonstrated. Total laser energy and efficiency with respect to deposited energy at pressure of 1.1 atm when the output distribution was non-uniform were found to be up to 200 J and 11%, respectively. The `jump' of pressure in SF6-H2 mixture at the instance of e-beam injection was found to be lower than that in excimer laser mixtures due to SF6 high density. This simplifies creation of wide-aperture e- beam HF-lasers. We expect that the use of pulse generators and wide-aperture laser setup available at HCEI enable us to develop 1 kJ non-chain HF laser initiated either by self- sustained discharge or e-beam.
Design and operating parameters of powerful KrCl((lambda) approximately 222nm), XeCl((lambda) approximately 308nm) excilamps with different discharge geometry pumped by continuous glow discharges along with Ar2((lambda) approximately 126nm) and Kr2((lambda) approximately 146nm) excilamps pumped by barrier discharge are presented. Excilamps with high spatial uniformity of the output and gas lifetime up to 100 hours were developed. It was shown that efficiency of luminescence of exciplex molecules of about 30 percent can be obtained in high-voltage glow discharge and positive column of glow discharge. Output at (lambda) approximately 222nm up to 200 W from single excilamp and 500 W from three excilamps, operated in parallel, was demonstrated.
Results of the experimental study of powerful lasers pumped by a radially convergent electron beam and powerful excilamps are presented. Laser radiation energies of 110, 90, 100, and 50 have been obtained at (lambda) equals 308, 249, 1730 and 2030 nm, respectively. Excilamp average power of 130 W have been obtained at (lambda) approximately 222 and 208 nm, the efficiency was up to 14%.
Simple readily manufacturable laser designs pumped by a self-sustained discharge are outlined. The outcomes of tests on laser action from exciplex molecules (ArF*, KrCl*, XeCl*, and XeF*) on electronic transitions in N2, N2+, F2, and F and vibration transitions in CO2 and HF are presented.
The results of an experimental study of coaxial exciplex lamps pumped by various types of discharge (the longitudinal discharge, barrier discharge, or continuous glow discharge) are presented. The mixture compositions and pressures as well as the pumping pulse parameters have been optimized for the production of radiation with (lambda) equals 350, 308, 249, 222, and 193 nm. Exciplex lamps with a radiating surface area of 570, 840 and 1300 cm2 have been created. The average radiation power achieved for (lambda) equals 222 nm is up to 4 W and for (lambda) approximately 308 and 350 nm is approximately 10 W. The possibility of an inductive energy store with a semiconductor opening switch being used for pumping a longitudinal-discharge-based exciplex lamp has been demonstrated.
E. Abdullin, Alexander Bugaev, S. Gorbachev, Anatoly Efremov, Boris Koval'chuk, Nikolai Koval, Sergey Loginov, Mikhail Lomaev, Victor Skakun, Victor Tarasenko, V. Tolkachev, Andrei Fedenev, E. Fomin, P. Shchanin
The results of an experimental study of the laser action on XeCl*, KrF*, and N2 molecules and by the atomic transitions of xenon and neon are presented. Laser radiation energies of 110, 90, 3, 100, 50, and 0.5 J have been obtained at (lambda) equals 308, 249, 358, 1730, 2030, and 585 nm, respectively. The experiments were carried out on two accelerators producing radially convergent electron beams, that pumped laser chambers 20 mm in diameter with a beam current of FWHM duration 0.3, 30, and 100 microsecond(s) .
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