Rate constants for the removal of O2 b1∑+g by collisions with O2, N2, CO2 and H2O have been determined at temperature 297 K. O2(b1 ∑+g) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed by observing the temporal behavior of the b1∑+g - X3∑-g fluorescence. The removal rate constants for CO2, N2 and H2O were not strongly dependent on temperature, and could be represented by the expressions kCO2=(1.8±0.05)×10-16; kN2=(2.2 ± 0.2)×10-15, and kH2O=(6.12±0.67)×10-12 cm3 molecule-1 s-1. Rate constant for O2(b1∑+ ) removal by O2(X), being orders of magnitude lower, represented by the fitted expression kO2=(3.67 ± 0.06)×10-17 cm3 molecule-1 s-1. All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.
A novel optical pumping scheme considering a two-step irradiation by light at wavelengths near 500 nm and 1315 nm is proposed in this work. Radiation at 500 nm is used to dissociate about 1% of iodine molecules. The radiation at 1315 nm excites atomic iodine to the 2P1/2 state. Singlet oxygen molecules are produced via the energy exchange process I(2P1/2)+O2(X3Σ)→ I(2P3/2)+O2(a1Δ), while I(2P1/2)+O2(a1Δ) energy pooling produces b1Σ oxygen. I(2P3/2) and O2(1Σ) then accelerate the dissociation of I2. After gas dynamic cooling in supersonic nozzle, active medium may reach ~100 W cm–2 and small signal gain of ~0.01 cm-1.
Results of experiments on dissociation of iodine molecules in the presence of singlet oxygen molecules are presented for wide range of oxygen-iodine media composition. Rate constants values have been obtained: 4.3⋅10-17cm3/s for the reaction O2(1Δ)+O2(1Δ)→O2(1Σ) +О2(3Σ) − (1), 2.8⋅10-13 cm3/s for the reactionO2(1Δ)+I(2P1/2)→O2(1Σ)+I(2P3/2) − (4) and 8.3⋅10-11 cm3/s for the reaction O2(1Σ) +I2→О2(3Σ)+2I − (2). Analysis of experiments shows that for the wide range of oxygen-iodine medium composition the dissociation occurs via the chain of reactions (1), (2), O2(1Δ)+I(2P3/2)→О2(3Σ)+I(2P1/2), (4) and via cascade process I2+I(2P1/2)→I2(v)+I(2P3/2), I2(v)+O2(1Δ)→2I+О2(3Σ). Contributions of each mechanism in the dissociation of the iodine are comparable for the typical composition of the active medium of the supersonic chemical oxygen-iodine laser. The experiments did not reveal the contribution of vibrationally excited oxygen molecules in the dissociation of iodine. Thus, the experiments and the following conclusions are fully confirmed iodine dissociation mechanism previously proposed by Heidner et al. (J. Phys. Chem., 87, 2348 (1983)).
KEYWORDS: Oxygen, Iodine, Molecules, iodine lasers, Chemical lasers, Gas lasers, Optical pumping, Chemical species, Active optics, Chemical oxygen iodine lasers, Laser optics, Semiconductor lasers, Aerospace engineering, Laser systems engineering
The kinetics of the processes in an O2/I2/Ar/H2O gas flow that is irradiated simultaneously by light at wavelengths near 500 nm and 1315 nm, is considered. Radiation at 500 nm is used to photodissociate about 1% of the iodine molecules. The radiation at 1315 nm excites atomic iodine to the 2P1/2 state. Singlet oxygen molecules are produced via the energy exchange process I(2P1/2)+O2(X3Σ) → I(2P3/2) + O2(a1Δ), while I(2P1/2)+O2(a1Δ) energy pooling produces b1Σ oxygen. I(2P1/2) and O2(b1Σ) then accelerate the dissociation of I2. This active medium may reach ~40 W/cm–2 at an optical efficiency of 50%.
KEYWORDS: Oxygen, Carbon dioxide, Molecules, Chemical analysis, Chlorine, Temperature metrology, Chemical lasers, Absorption, Spectroscopy, Chlorine gas
Measurements of the absolute spectral irradiance from O2(a)-O2-H2O gas, produced by a chemical singlet oxygen
generator, were performed. FWHM of singlet oxygen collision induced emission (CIE) at 634 and 703 nm have been
measured in the temperature range 150-400 K. The measured rate constant of CIE at 634 nm - (6.72±0.8)×10-23 cm3/s is
in agreement with the value of the band intensity of the collision induced absorption. The rate constant of CIE at 703 nm
relates to the rate constant of CIE at 634 nm as 1.06. The efficient rate constant of 8×10-17cm3/s for the reaction
O2(a)+O2(a)→"products" at about 360 K and the rate constant of (4.4±1)×10-17 cm3/s for the reaction
O2(a)+O2(a)→O2(b)+O2 at about 330 K have been measured. These rates are larger than listed in the standard chemical
oxygen-iodine laser (COIL) package. Nonequilibrium fraction of O2(b,v=1) was measured against water fraction. It was
deduced that the maximum number of oxygen vibrational quanta, generated in the sequences of the reactions
O2(a)+O2(a)→O2(b)+O2, O2(b)+H2O→O2+H2O, is less than 0.05. The analysis predicts that the fraction of
vibrationally excited oxygen molecules at the exit of most-used chemical SOG most likely corresponds to the thermal
equilibrium. Analysis of the data obtained from the tests of jet type SOG predicts O2(a) nascent yield of about 90%.
Experiments were carried out with a subsonic chemical oxygen-iodine laser (COIL), equipped with an electric discharge
generator of iodine atoms. CH3I entrained in a carrier flow of Ar was used as atomic iodine precursor. About 50% of
iodine contained in CH3I molecules was extracted in the generator. Up to 3.5% of electric power loaded into the
discharge was spent on CH3I dissociation. A straightforward comparison of COIL performance for two cases -
conventional, when I2 was injected in the singlet oxygen flow and when iodine atoms produced externally together with
other discharge products were injected - was made. In the latter case nearly four times increase in output power was
observed.
An efficient and compact centrifugal bubbling SOG was employed as energy source in supersonic COIL. A centrifugal
bubbling SOG generated gas at 100 torr of total pressure providing 90% of chlorine utilization and 60% of O2(1Δ) yield
with efficient depletion of BHP chemicals in single pass through SOG. A 1 kW class ejector COIL powered by this SOG
demonstrated a specific power of 12.5 W per 1cm3/s of BHP volumetric rate at chemical efficiency 22.7%.
A centrifugal bubbling SOG generated gas flow with partial oxygen pressure up to 40 torr at singlet oxygen yield about
60% and residual chlorine less than 10%. At initial BHP temperature 260K and ratio of chlorine molar flow rate to BHP
volumetric rate of 1mole/litre the output BHP temperature was 290K and water vapor fraction relative to the oxygen was
15%. An oxygen flux up to 6 mmole/s per 1 cm2 of the bubbler surface has been attained. An ejector nozzle bank generates gain medium flow at Mach number ~2 and temperature lower 200K with small signal gain higher 1%/cm. Ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of BHP volumetric rate.
A centrifugal bubbling SOG is a perspective source of oxygen at high pressure with high depletion of the BHP in the single burn dawn. The theoretical estimations show that at high centrifugal acceleration gas-liquid contact specific surface 30cm-1, frequency of the surface renewal can less than 10-3s and bubble rise velocity up to 500 cm/s be realized in the bubble SOG. The results of the measurements of O2(1&Dgr;) yield, chlorine utilization and water fraction at the exit of the centrifugal bubble SOG are presented. A high O2(1&Dgr;) yield and chlorine utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface. The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of the BHP volumetric rate.
An ejector nozzle bank powered by centrifugal bubbling SOG is considered like highly efficient gain generating system
for COIL. A high potential recovered pressure ~100 torr of the gain medium flow with a small signal gain higher than
1% cm-1 and low oxygen plenum pressure has been demonstrated. A centrifugal bubbling SOG is an efficient source of
oxygen at high pressure with high depletion of the BHP in the single burn dawn. A high 02(1&Dgr;) yield and chlorine
utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface.
The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power
6 kJ per 1 litre of the BHP in the single burn dawn. The combination of centrifugal bubble SOG with ejector nozzle bank
can be considered as a promising gain medium flow generation system for COIL.
°The cross-flow SOG with filament-guided jets (FJSOG) was developed for COIL. It was found that chlorine utilization strongly depended on chlorine molar flow rate and BHP volumetric rate, and slowly depended on the working pressure for fixed chlorine molar flow rate. The increase of BHP temperature from -25°C to -7C resulted in the increase of chlorine utilization and water vapor fraction in the gas flow from FJSOG. The supersonic COIL with ejector nozzle bank was supplied by oxygen flow from FJSOG. The FJSOG worked very stable without droplet carry out and in laser experiments the clogging of nozzles by dry deposit was not observed. The chemical efficiency more than 24% have been obtained in ejector COIL driven by FJSOG.
Experimental results of investigation of the ECOIL with supersonic nozzles for driver N2 are presented. Employment of the supersonic nozzles and extremely high-pressure driver nitrogen gives possibility to minimize the plenum oxygen pressure at high oxygen flux, to reach high gain and chemical efficiency.
The activity of development a COIL with high potential recovered pressure, high gain and efficiency is described. Two nozzle banks with conical supersonic nozzles for the driver nitrogen but with different nozzle arrangements have been developed for generation of the gain flow of chemical oxygen-iodine laser. The nozzle banks were supplied by oxygen flow from the cross-flow singlet oxygen generator with filament-guided jets. Results of aerodynamic tests, visualization of flows by laser induced fluorescence, scanning of the excited iodine atoms distribution and laser power extraction are presented. The efficient penetration of the driver buffer flow into the gain flow was observed at distances less than 100 mm from the nozzle banks. The total power exceeding 1 kW with chemical efficiency more than 24% was obtained in 5 cm gain length COIL without helium dilution. The lasing was observed for both nozzle banks at total mirror transmission more than 10%.
The historical ejector-like chemical oxygen iodine laser (COIL) contribution at the Lebedev Physical Institute, Samara Branch is briefly presented. Two possible schemes of such COIL which provide the high exhaust pressure are considered. The high-pressure hot driver nitrogen is carrier of iodine vapor in the first scheme. In the second version the additional nozzles with the low-pressure secondary nitrogen are employed for injection iodine vapor but the pure high-pressure driver nitrogen has the room temperature. The last COIL version was investigated in Lebedev Physical Institute in more detail and results of these investigations are presented. This ejector nozzle bank generates gain medium with high Mach number, low temperature and high gain. A high chemical efficiency up to 25% and the potential pressure recovery up to 90 torr have been achieved simultaneously.
A one-dimensional kinetic computer model of the subsonic Chemical Oxygen-Iodine Laser (COIL) is discussed. The computational results are used for a re-interpretation of data published earlier on the performance of a subsonic COIL experimental device in the Institute of Physics, Prague.
Experimental lasing results for the Chemical Oxygen Iodine Laser, (COIL), using four different ejector nozzle configurations are presented. These nozzle banks differed in the location of Iodine injection, the area of the oxygen nozzles, and the nozzle contour of the primary driver nitrogen. The aerodynamic choking of the oxygen jets caused by the under expanded primary driver nitrogen resulted in a reduction of the O2 (1(Delta) ) yield and chemical efficiency. Dilution of chlorine with helium in the ratio of 1:1 reduces the partial pressure of oxygen and increases the velocity resulting in a chemical efficiency of 25% at 250 mmoles/sec and 23% at 500mmoles/sec of driver nitrogen respectively. The corresponding Pitot pressures are 50 and 90 torr.
The developed supersonic COIL with 5 cm gain length was driven by Verti Jet SOG having 0.28 liter of working volume. The oxygen was diluted by the primary nitrogen downstream from the JSOG. Two types of nozzles were tested: single throat nozzle with 10 mm throat height and double throat height 15 mm. The COIL with single throat nozzle operated at the primary nitrogen dilution O2:N2 equals 1:1 and the chlorine flow rate less than 40 mmole/s to maintain the designed gas flow conditions in the reactor of JSOG. The maximum power 765 W has been achieved at 39 mmole/s of the chlorine molar flow rate. The using of double throat nozzle allowed to increase chlorine moral flow rate up to 75 mmole/s. In this case the maximum power 1.4 kW has been reached for primary nitrogen ratio O2:N2 equals 1:1.28. The specific performance so f 5 kW per 1 liter of the reactor volume, of 100 W/cm2 per unit of the stream cross section are in the cavity and of 2,7W of the pump capacity were obtained.
The axial flow COIL is a convenient device to study the gain and storage energy life-length along the gas flow. When the velocity of the axial flow close to the sonic velocity and the active medium is preliminary cooled the conditions like in the supersonic transverse flow COIL can be realized. The presented axial flow COIL was driven by jet type SOG. The next gas flow rates were used in all experiments: 20 mmole/s of the primary buffer gas, 10 mmole/s of secondary buffer gas and 10 mmole/s of chlorine through the jet SOG. The maximum output power 106 wt was obtained at ~0.05 mmole/s of the iodine flow rate with primary and secondary nitrogen buffer gas. The cooling of the primary nitrogen to 80°K resulted in 130 wt output power. The using helium at 80°K instead of nitrogen resulted in 186 wt output power or 20.5% total chemical efficiency for 0.1 mmole/s of the iodine flow rate. The exposition of the laser beam at the black wood target showed that the main part of laser power was inside the circle 22 mm in diameter.
KEYWORDS: Chemical oxygen iodine lasers, Oxygen, Iodine, Chlorine, Laser resonators, Chemical lasers, Nitrogen, Industrial chemicals, Chemical analysis, Chlorine gas
The chemical oxygen-iodine laser (COIL) is a scaleable high power laser promising for industrial applications. The principles of singlet oxygen generation in the jet type singlet oxygen generator and COIL operation are considered. The progress in high pressure jet type singlet oxygen generators allowed to develop the compact highly efficient COIL. The different types of efficient mixing schemes were tested in COIL based on the high pressure jet singlet oxygen generator. The preliminary cooling of active medium via mixing of oxygen with cold buffer nitrogen gas result in high efficiency operation of the small scale COIL with subsonic gas flow in the laser cavity. The project of COIL with high pressure of oxygen in laser cavity is discussed.
The experimental results of study of sub- and supersonic chemical oxygen-iodine lasers (COIL) based on the jet type singlet oxygen generator are presented. The progress in the high pressure jet type singlet oxygen generators allowed to develop the compact highly efficient COIL. The different types of the mixing schemes were tested in supersonic COIL based on the high pressure jet singlet oxygen generator. The preliminary cooling of the active medium by mixing of oxygen with the cold buffer nitrogen gas results in high efficiency operation of the small scale COIL with subsonic and supersonic gas flow in the laser cavity. In COIL with the fast axial gas flow the chemical efficiency more than 20% was achieved.
The mechanism of Cl2 absorption and O2(1(Delta) ) generation in JSOG were considered. The concentration of oxygen dissolved in BHP can in 103 times more than equilibrium oxygen concentration. But it is not enough for spontaneous generation of oxygen bubbles. The 'burying' of oxygen into bulk of BHP occurs during macroscopic renewal of BHP surface. It was found that this effect doesn't result in essential O2(1(Delta) ) yield decreasing. Three dimensionless criteria have been derived from one-dimensional model for dynamic scaling of JSOG. The approximate values of these criteria were calculated to achieve 90% Cl2 utilization and 60% O2(1(Delta) ) yield. The measurements of Cl2 utilization and O2(1(Delta) ) yield from JSOG allowed to make more precisely these three criteria. It was found that the rate of chlorine absorption in JSOG is higher than it follows from one-dimension model. It was explained by hydrodynamic renewal of surface of BHP jets. The O2(1(Delta) ) yield from JSOG is less than calculated according to one-dimension model. It was explained by additional unknown reactions in reaction zone of JSOG. The dimensionless criteria can be used for the first step of scaling of JSOG. The droplet content at the exit of JSOG with vertical gas outlet is expected to be less than in JSOG with side gas outlet. The Verty-JSOG with initial Cl2 flux 8 mmole/s/cm2 is projected.
We report on studies of a 5 cm gain length chemical oxygen- iodine laser (COIL) energized by a jet-type singlet oxygen generator (JSOG) are presented. For 10 mmole/s of Cl2 flow rate, output power of 132 W with chemical efficiency of 14.5% were obtained without a water vapor trap. One-hundred-sixty- three watts and 18% were achieved when cooled (173 K) He was introduced downstream of the JSOG; under these conditions the small signal gain was estimated to be 0.32% cm-1. Wattage of 190 and 10.5% were obtained for 20 mmole/s of Cl2 flow rate. Replacing He by N2 as a buffer gas resulted in a 13% power decrease only. The main key for increasing the chemical efficiency of a COIL without a water vapor trap for a given iodine-oxygen mixing system is found to be high oxygen pressure and low water vapor pressure inside the reaction zone of the JSOG. The last goal was achieved by optimizing the composition and temperature of the basic hydrogen peroxide solution (BHP). The experimental results are discussed and related to the composition and flow conditions of the gaseous reactants and of the BHP. We also report on preliminary results of efficient COIL operation without primary buffer gas using rectangular nozzles with iodine injection in the throat.
Experimental investigation of a jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was performed aimed to evaluation of the effects of BHP temperature and composition on the water content and other output generator parameters. Laser experiments on a small-scale system were realized to prove the obtained results.
The increasing of stagnation pressure and Re number of gas flow is a very important for supersonic oxygen-iodine laser (COIL). This goal can be achieved with the aid of high pressure singlet oxygen generator (SOG) and high dilution of oxygen with buffer gas of high molecular weight downstream of SOG. The study of COIL operated with jet type SOG at 10 and 20 mmole/s of chlorine flow rate and 50 torr output of pure oxygen is presented. Two experimental set-up were tested. In the first one the mixing of chlorine with buffer gas was provided upstream of SOG gas inlet. In the second one the pure chlorine was injected into SOG and oxygen was mixed with buffer gas downstream of SOG outlet. The stability of jet SOG in the first set-up strongly depended on partial buffer gas pressure and its molecular weight: at higher pressures and molecular weight the stability of SOG operation was worse. In the second set-up the operation of SOG didn't depend on buffer gas pressure and its molecular weight. COIL output power was highest for first set-up with dilution of chlorine by buffer gas until SOG stable operated. In the second set-up the output power was in twice less and strongly depend on type and position of buffer gas injector between SOG and iodine injector. This dependence strongly demonstrated the importance of gas mixing to molecular level for achieving highest COIL power. Another problem considered in this work is connected with BHP heating that important for recirculation of liquid in long time duration COIL operating system. The correlation of BHP heating and O2(1(Delta) ) yield is presented. It is shown that nacsent O2(1(Delta) ) yield is close to 100%.
Jet singlet oxygen generator (JSOG) is one of the most efficient sources of electronically excited O2(1(Delta) ). The JSOG can operate at very high partial O2(1(Delta) ) pressure. This feature of JSOG allows supersonic COIL operation without water vapor trap. The prediction of output parameters of JSOG is very important for correct design and engineering of COIL. The one-dimensional model of JSOG has been developed to predict output parameters (chlorine utilization, O2(1(Delta) ) yield). The comparisons of calculated and measured output parameters are presented. The main attention is paid to discrepancies of calculated and measured output parameters and limitation of the one-dimensional model. It is shown that for extremely high pressure JSOG the role of effects that cannot be included into a one-dimensional model is very important. The difference between input and output BHP temperature in JSOG is correlated with chlorine utilization and O2(1(Delta) ) yield.
KEYWORDS: Liquids, Chemical lasers, Chlorine, Throat, Chemical oxygen iodine lasers, Oxygen, Absorption, Resistance, Thermal effects, High power lasers
Results of experimental and theoretical study of the liquid jet O2(1(Delta) ) generator in P.N. Lebedev Institute Samara Branch are presented. This study includes hydrodynamic and gasdynamic effects, heat and mass transfer, droplet generation and separation. The dependence of O2(1(Delta) ) and Cl2 yields on geometrical and physical parameters of generator are presented. High O2(1(Delta) ) yield and operation of small scale subsonic chemical oxygen-iodine laser up to 100 torr of active gas pressure in jet liquid generator have been achieved. Counterflowing jet liquid O2(1(Delta) ) generator is a very perspective for high power supersonic oxygen-iodine laser without water vapor trap and droplet separator.
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