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Superlinear Enhancement of Discharge Driven Electric Oxygen-Iodine Laser by Increasing
Abstract
Continuing experiments with electric oxygen-iodine laser (ElectricOIL) technology have significantly increased laser power output by increasing the product of gain and gain-length, . The authors report on progress with recent ElectricOIL devices utilizing a new concentric discharge geometry with improved production at higher discharge operating pressure at higher system flow rates. produced in flowing radio-frequency discharge in gas mixture is used to pump by near-resonant energy transfer, and laser power is extracted on the transition at 1315 nm. Advancements in heat exchanger design reduce wall loss without sacrificing significant cooling efficiency improving best gain performance from 0.26 to 0.30% . Modeling of recent data is presented. By increasing the gain length (system size) by a factor of 3, a 5-fold increase in laser output on the 1315-nm transition of atomic iodine was achieved. Flow conditions with were used to extract a continuous wave average total laser power of 481 W. A low frequency oscillation in the total power was observed giving a peak outcoupled power of 538 W.
... Since the first reporting of a viable electric discharge driven oxygen-iodine laser system (also often referred to as ElectricOIL or DOIL in the literature), there have been a number of other successful demonstrations of gain and laser power; Ionin [Ionin, 2007] and Heaven [Heaven, 2010a] provide comprehensive topical reviews of discharge production of O2(a) and various EOIL studies. The highest EOIL output power reported to date is > 500 W and the technology shows superlinear scaling with g0L [Benavides, 2012]. Computational modeling of the discharge and post-discharge kinetics [Stafford, 2004;Palla, 2006;Palla, 2007;Palla, 2010] has been an invaluable tool in EOIL development, allowing analysis of the production and depletion of various discharge species [such as O2(a), O2(b 1 ), O-atoms, and O3] and determination of the influence of NOX species on system kinetics. ...
... During the evolution of the EOIL technology development it became clear that it was critical to create post-discharge heat exchangers (HXs) that would significantly cool the gas flow while simultaneously (i) minimizing any loss of the critical O2(a), (ii) significantly reducing the detrimental O-atoms, and (iii) minimizing pressure drop for downstream pressure recovery reasons. This led to a series of BLAZE studies in which different geometries of cross-flow HXs were tested to guide the design of the HX to be utilized in the 7 th generation EOIL cavity (CAV7) [Benavides, 2012;Benavides, 2014]. While a diamond shaped tube provided the best characteristics in the original survey [Benavides, 2014], a simple circular tube was found to provide adequate performance and was much more affordable to manufacture. ...
... Classic shock diamonds are present inside the nozzle, Fig. 10; the simulations are in excellent agreement with the experimental data including the predicted total outcoupled power of 200 mW, which is in excellent agreement with the 220 mW measured experimentally. While these simulations were performed for relatively early EOIL experiments, the hardware has since been dramatically improved to attain a gain of 0.30% cm -1 and laser power > 500 W [Benavides, 2012]. Figure 1 shows plasma simulations of the concentric EOIL discharge tubes used in Cav7 [Benavides, 2012], as well as 3D nozzle simulations illustrating the O2(a) concentration and the lasing mode of an earlier Cav5 system [Zimmerman, 2009]. ...
... Influence of molecular oxygen on iodine atoms production in an RF discharge P A Mikheyev 1,2 , N I Ufimtsev 1 , A V Demyanov 3 , I V Kochetov 3 , V N Azyazov 1,2 and A P Napartovich 3 Second, I 2 strongly deactivates I * , leading to energy loss, limiting the optimal [I] and small-signal gain. In the absence of I 2 , the optimal [I] and gain in the active medium could be increased. ...
... Glow discharges had proved to be suitable for atomic iodine production out of different precursor molecules both in dc and pulsed regimes [3][4][5][6][7]. An advantage of using precursors instead of molecular iodine is a small fraction of I 2 at the discharge generator outlet, because it is formed in discharge plasma only through the recombination of iodine atoms. ...
... Diffusion frequencies ( = × v D r 5.78 2 , where D-diffusion coefficient, r-tube radius) for I, O atoms and CH 3 radicals in Ar mixtures were equal to ~300, 800 and 630 s −1 , and in He-900, 1600 and 1400 s −1 , correspondingly. The probability of surface recombination for I atoms, CH 3 and O was chosen to be 1, although there are indications that on a clean surface for I atoms it might be considerably smaller [46] down to 10 −3 ÷ 10 −4 . Also, processes (15)-(16), (62)-(63), (96)-(97) and (99) with participation of CH 2 I 2 ; processes (17)-(21), (68)-(72), (78)-(79) with participation of C 2 H 6 and CH 4 and process (73) were added. ...
The results of the experiments and modeling of CH3I dissociation in a 40 MHz RF discharge plasma are presented. A discharge chamber of an original design, consisting of quartz tubes between two planar electrodes, permitted us to produce iodine atoms with a number density up to 2 × 1016 cm-3. In this discharge chamber, contrary to the previous experiments with a DC discharge and RF discharge with bare planar electrodes, contamination of the walls of the tubes did not disturb discharge stability, thus increasing iodine production rate. A substantial increase in CH3I dissociation efficiency due to the addition of oxygen into Ar(He) : CH3I mixtures was observed. Complete CH3I dissociation in the Ar : CH3I : O2 mixture occurred at 200 W discharge power, while a fraction of discharge power spent on iodine atoms production at 0.17 mmol s-1 CH3I flow rate amounted to 16%. Extensive numerical modeling showed satisfactory agreement with the experiments and permitted us to estimate a previously unknown rate of constants for the processes: Ar∗ + CH2I2 → Ar + CH2 + I + I - 1.5 × 10-11 cm3 s-1; Ar∗ + CH2I2 → Ar + CH2I+ + I + e - 10-11 cm3 s-1. Also, the cross section for the process CH2I2 + e → CH2 + I + I + e was estimated to be five times smaller than for the analogous process with CH3I.
... Influence of molecular oxygen on iodine atoms production in an RF discharge P A Mikheyev 1,2 , N I Ufimtsev 1 , A V Demyanov 3 , I V Kochetov 3 , V N Azyazov 1,2 and A P Napartovich 3 Second, I 2 strongly deactivates I * , leading to energy loss, limiting the optimal [I] and small-signal gain. In the absence of I 2 , the optimal [I] and gain in the active medium could be increased. ...
... Glow discharges had proved to be suitable for atomic iodine production out of different precursor molecules both in dc and pulsed regimes [3][4][5][6][7]. An advantage of using precursors instead of molecular iodine is a small fraction of I 2 at the discharge generator outlet, because it is formed in discharge plasma only through the recombination of iodine atoms. ...
... Diffusion frequencies ( = × v D r 5.78 2 , where D-diffusion coefficient, r-tube radius) for I, O atoms and CH 3 radicals in Ar mixtures were equal to ~300, 800 and 630 s −1 , and in He-900, 1600 and 1400 s −1 , correspondingly. The probability of surface recombination for I atoms, CH 3 and O was chosen to be 1, although there are indications that on a clean surface for I atoms it might be considerably smaller [46] down to 10 −3 ÷ 10 −4 . Also, processes (15)-(16), (62)-(63), (96)-(97) and (99) with participation of CH 2 I 2 ; processes (17)-(21), (68)-(72), (78)-(79) with participation of C 2 H 6 and CH 4 and process (73) were added. ...
Results of experiments and modeling of CH3I dissociation in a 40 MHz RF discharge in a discharge chamber of original design to produce iodine atoms for cw oxygen-iodine laser are presented. In experiments a substantial increase in CH3I dissociation efficiency due to addition of oxygen into Ar:CH3I mixture was observed. Complete CH3I dissociation in Ar:CH3I:O2 mixture occurred at 200 W discharge power. Fraction of discharge power spent on iodine atoms production was equal to 16% at 0.17 mmol/s CH3I flow rate. The rate of carbon atoms production as a function of molecular oxygen and water contents in CH3I:Ar mixtures was studied with the help of numerical modeling. It was found that addition of water vapor resulted in increase while addition of molecular oxygen and HI in decrease of the rate of carbon atoms production. Due to diffusion most of carbon atoms had enough time to deposit on the walls of the discharge chamber. However, contrary to the situation in a DC discharge, in the RF discharge accumulation of carbon on the walls of the discharge chamber did not hamper discharge stability and iodine production, as it was observed in our experiments.
... Ionin et al. [Ionin, 2007] and Heaven [Heaven, 2010a] provide comprehensive topical reviews of discharge production of O 2 (a) and various ElectricOIL studies. The highest gain in an ElectricOIL device reported to date is 0.30 % cm -1 [Benavides, 2012], and the highest output power reported is 538 W [Benavides, 2012]. ...
... Ionin et al. [Ionin, 2007] and Heaven [Heaven, 2010a] provide comprehensive topical reviews of discharge production of O 2 (a) and various ElectricOIL studies. The highest gain in an ElectricOIL device reported to date is 0.30 % cm -1 [Benavides, 2012], and the highest output power reported is 538 W [Benavides, 2012]. ...
... Some trade studies used to develop heat-exchangers for ElectricOIL are summarized in [Woodard, 2011] and . The design used in Cav7 experiments is reported in [Benavides, 2012]. ...
Over the last decade new advanced gas lasers have emerged as possible candidates for high power laser systems that may supplant more conventional chemical and gas laser systems. Among these are the electric oxygen-iodine laser (ElectricOIL), the diode pumped alkali laser (DPAL), the exciplex pumped alkali laser (XPAL), and the optically pumped metastable rare gas laser. In this paper we will primarily focus on the ElectricOIL and XPAL systems, and discuss some of the recent experiments and modeling of these systems. © 2012 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc.
... Experiments [1] with Electric Oxygen-Iodine Laser (ElectricOIL) heat exchanger technology have demonstrated improved control of oxygen atom density and thermal energy, with minimal quenching of O 2 (a 1 ), and increasing small signal gain from 0.26% cm -1 to 0.30% cm -1 . Heat exchanger technological improvements were achieved through both experimental and modeling studies, including estimation of O 2 (a 1 ) surface quenching coefficients for select ElectricOIL materials downstream of a radio-frequency discharge-driven singlet oxygen generator. ...
... Ionin [16] and Heaven [17] provide comprehensive topical reviews of discharge production of O 2 (a) and various ElectricOIL studies. Currently, the highest reported peak gain and laser power in an ElectricOIL device are 0.30% cm −1 and 538 W, respectively [1] . ...
... Thinner walls lead to greater temperature gradients, yielding comparable bulk flow temperature reduction with less surface area (better preserving the O 2 (a) population). The fundamental goal of these investigations was to define the STER-7 geometry for the 7 th generation ElectricOIL cavity [1] (CAV7). ...
Experiments[1] with Electric Oxygen-Iodine Laser (ElectricOIL) heat exchanger technology have demonstrated improved control of oxygen atom density and thermal energy, with minimal quenching of O2(a1Δ), and increasing small signal gain from 0.26% cm-1 to 0.30% cm-1. Heat exchanger technological improvements were achieved through both experimental and modeling studies, including estimation of O2(a1Δ) surface quenching coefficients for select ElectricOIL materials downstream of a radio-frequency discharge-driven singlet oxygen generator. Estimation of O2(a1Δ) quenching coefficients is differentiated from previous studies by inclusion of oxygen atoms, historically scrubbed using HgO[2-4] or AgO[5]. High-fidelity, time-dependent and steady-state simulations are presented using the new BLAZE-VI multi-physics simulation suite[6] and compared to data.
... %/cm were previously established and implemented in the development of a 7 th generation laser cavity denoted "Cav7". In this paper, the authors report on design improvements leading to the demonstration of the Cav7 ElectricOIL device having a 5-fold improvement in outcoupled laser power with only a 3-fold increase in device size [Benavides, 2012]. ...
... Some trade studies used to develop heat-exchangers for ElectricOIL are summarized in [Carroll, 2011] and [Zimmerman, 2009]. The design used in Cav7 experiments is altered from the staggered-tube device used for Cav6 [Carroll, 2011]; the new HX having less surface area to reduce O 2 (a) loss, better optimized tube spacing to further reduce pressure loss, and more even coolant distribution to maximize temperature reduction [Benavides, 2012]. ...
Continuing experiments with Electric Oxygen-Iodine Laser (ElectricOIL)
technology have significantly increased laser power output by increasing
the product of gain and gain-length, g0L. The authors report on progress
with recent ElectricOIL devices utilizing a new concentric discharge
geometry with improved O2(a1▵) production at higher
discharge operating pressure at higher system flow rates.
O2(a1▵) produced in flowing radio-frequency discharge in
O2- He-NO gas mixture is used to pump I(2P1/2) by near-resonant energy
transfer, and laser power is extracted on the I(2P1/2) -->
I(2P3/2) transition at 1315 nm. Modeling of recent data is
presented. By increasing the gain length (system size) by a factor of 3,
a 5-fold increase in laser output on the 1315-nm transition of atomic
iodine was achieved. Flow conditions with g0L = 0.042 were used to
extract a continuous wave (CW) average total laser power of 481 W. A low
frequency +/-11.9% oscillation in the total power was observed giving a
peak outcoupled power of 538 W.
... The most common application of a DBD is ozone production [17,18]. DBD was also studied for plasma assisted combustion [19], and a radio frequency DBD-even for singlet oxygen [20] and iodine atoms [21] production for oxygeniodine laser. ...
This paper describes the results of modeling of a dielectric barrier discharge (DBD). Filamentary structure of DBD is taken into account in the model by introducing the ratio of the cross section area of a microdischarge to the electrode area as a parameter of the model. Discharge and afterglow stages in the gas flow were studied using a zero-dimensional model for a DBD microdischarge channel. The results of modeling are compared with literature data for [O] number densities in a single pulse nanosecond discharge, and with our own measurements of ozone formation in the DBD. Measurements of ozone number density in oxygen and in mixtures of oxygen with methane served as means of validating the DBD model. The best agreement of the calculated and experimental dependences of [O3] number densities on the discharge energy load was observed, when processes involving vibrationally excited ozone were accounted for together with the discharge microstructure.
... For the typical post-discharge conditions37 : [He]= 9×10 17 cm -3 , [O 2 ]= 2.5×10 17 cm -3 , [O]=5×10 15 cm -3 , [O 2 (a)]=3×10 16 cm -3 , T=550 K the terms in the denominator satisfy the oxygen quenching rate in process (3) is limited by O 3 (υ) formation rate in the three-body recombination process (2). This is the reason way the authors of Ref. 15 was inclined to conclude that the O 2 (a 1 Δ) deactivation in the O/O 2 /O 2 (a 1 Δ) mixture is a three-body process. ...
The development of a discharge oxygen iodine laser (DOIL) requires efficient production of singlet delta oxygen O2(α1 Δ) in electric discharge. It is important to understand the mechanisms of of O2α1 Δ) quenching in these devices. To gain understanding of this mechanisms quenching of O2(α]1 Δ)in O/O2/O3/CO2/He mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(α1Δ) quenching were followed by observing the 1268 nm fluorescence of O2α1 Δ → X3∑ transition. It is shown that vibrationally excited ozone O3(v) formed in the three-body recombination O + O2+ M →O3(v) + M is an important O/O2/O3 quenching agent in O/O2/O3 systems. The process O3(v ≥2) + O2(a1 Δ)→ 2O2 + O is the main O2(α1 Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease oxygen atom concentration, the contribution of this process into overall O2(α1Δ) removal is significant even in the discharge zone. It was found in experiment that addition of species that are good quenchers of O3 decrease O2(a1 Δ) deactivation rate in the O/O2/O3 mixtures.
The single-frequency two-level (SFTL) generation model was applied to predict the power extraction efficiency in electrically driven oxygen-iodine laser (EOIL). The analysis of the calculated and published experimental data showed that power extraction from the cw EOIL is limited by the rate of energy transfer from singlet oxygen molecules O2(1") to iodine atoms I(2P3/2) and about half of the produced singlet oxygen molecules were carried out from the resonator. To increase power extraction efficiency it will be necessary to substantially extend concentrations of singlet oxygen molecules and iodine atoms in the active medium of EOIL.
The kinetics of the processes occurring in an O2-I2-He-H2O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the 2P1/2-2P3/2 transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen-iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O2(a1Δ) exceeding 10 %. Having formed a supersonic gas flow with a temperature ∼100 K from this medium, one can reach a small-signal gain of about 10-2 cm-1 on the 2P1/2-2P3/2 transition in iodine atoms. The specific power per unit flow cross section in the oxygen-iodine laser with this active medium may reach ∼100 W cm-2.
We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O-2(a(1)Delta) + O-3(v) -> 2O(2) + O on the removal rate of O-2(a(1)Delta) in an electric-discharge-driven oxygen-iodine laser. This reaction has been shown to be a major channel of O-2(a(1)Delta) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O-2(a(1)Delta) in the discharge region of the generator.
A simplified single-frequency two-level model for predicting power extraction from a CW oxygen-iodine laser (OIL) considering relaxation losses has been developed. The model predicts that the energy efficiency of CW OILs with stable resonators depends on three similarity criteria. Criterion γd is the ratio of the residence time of active medium in the resonator to the singlet oxygen O2(1triangle) energy extraction time at an infinite intraresonator intensity. Criterion Π is small-signal gain to the threshold ratio. Criterion Λ is the relaxation to excitation rate ratio for the electronically excited iodine atoms I(2P1/2). The analysis of the calculated and experimental data show that effective power extraction from the CW OIL active medium is achieved when the values of the similarity criteria are in the ranges: γd=4-6, Π = 3-8, and Λ ≤ 0.01.
Continuing experiments with Electric Oxygen-Iodine Laser (EOIL)
technology have significantly increased laser power output by increasing
the product of gain and gain-length, g0L. Increasing the
system size by a factor of 3 resulted in a 5-fold increase in laser
output on the 1315-nm transition of atomic iodine. The peak output power
observed was 538 W.
Nowadays, the shift towards cloud computing services is rapidly increasing. Organizations are leaning more towards adopting cloud-based services to increase their computation and processing power with reduced operational and maintenance costs. Similarly, being in the information age where huge amounts of information are generated daily from multiple interconnected systems makes it more challenging to absorb this information and make accurate informed decisions. Thus, the need for an automated well-structured approach for decision making is evident. Decision Support Systems (DSS) are interactive software-based systems that play a fundamental role as a technology enabler to provide analytical and visualization capabilities to support decision makers make accurate decisions. In this paper, we present an architecture framework for building a cloud-based distributed DSS to facilitate the decision making process for the planning and design of complex systems. The framework provides a group decision making platform to be utilized by different stakeholders. The framework offers a web portal that leverages a collection of new, open-source technologies and protocols as well as open standards. These are important for interoperable access across technologies, platforms, and mobile devices.
Experiments and modeling have led to continued enhancements in the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production of O 2 (a) in a radio-frequency (RF) discharge in an O 2 /He/NO gas mixture. New discharge geometries and increases in gain length, flow rates, discharge power, and resonator mode volume have improved the peak measured gain to 0.26% cm -1 and the outcoupled laser power to 102 W. The BLAZE model has been used to perform end-to-end (discharge though laser resonator) simulations of the new system configuration to help guide this process. Results are in good agreement with data. Additional measurements of gain recovery downstream of an operating laser cavity for five cases of interest are presented and modeled. The deviation of the gain recovery data from calculations based on presently accepted theory is highlighted. Several potential mechanisms to explain this theory are presented and discussed.
Experiments and modeling have led to continued enhancements in the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production of O 2 (a) in a radio-frequency (RF) discharge in an O 2 /He/NO gas mixture. New discharge geometries have led to improvements in O 2 (a) production and efficiency. Studies of electrode gap continue to improve O 2 (a) production at high pressures. Additionally, measurements of species exiting the discharge and the determination of discharge parameters such as E/N continue to expand the understanding of this system. Some of these improvements have already been applied to the laser system, and other advances will be utilized to continue scaling the system to higher laser powers. Over 1 kW of power stored in O 2 (a) has been demonstrated in both the rectangular cross-section and multi-circular tube discharges.
The authors observed 95% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine for only a 50% increase in gain length (5.1 cm to 7.6 cm), flow rates, and discharge input power, making use of a large volume 16-mm gap transverse discharge. A gain of 0.26% cm -1 was obtained and the laser output power was 55 W in a stable resonator with two 5 cm (2-in.) diameter, 0.9970 reflective mirrors. A longer gain length cavity permits use of lower reflectivity resonator mirrors that reduce diffractive spill losses, and thereby extract power from the gain medium more efficiently. The outcoupled power was increased to 92 W by increasing the mirror diameter to 10 cm (4-in.), demonstrating that significantly higher power was available in the electric oxygen-iodine laser gas flow which could be extracted by tailoring the cavity design. Two 4-mirror folded resonator configurations using 5 cm optics were also demonstrated, a stable "Z-resonator" with a z-shaped optical path having six roundtrip passes through the gain medium, and a stable "X X-resonator" having four roundtrip passes through the gain medium. The best measured outcoupled powers for these folded designs were 102 W and 109 W for the Z-resonator and X-resonator, respectively. Continued expansion of the operating envelope to higher flow conditions, pressures, and gain length of the laser cavity, plus the addition of an iodine pre-dissociator discharge are expected to provide significant increases to the gain and laser power. The results presented herein represent more than two orders of magnitude improvement in gain and laser power since the initial demonstration in 2005.
Experiments and modeling have led to a continuing evolution of the
Electric Oxygen-Iodine Laser (ElectricOIL) system. A new concentric
discharge geometry has led to improvements in O2(a) production and
efficiency and permits higher pressure operation of the discharge at
high flow rate. A new heat exchanger design reduces the O2(a) loss and
thereby increases the O2(a) delivered into the gain region for a
negligible change in flow temperature. These changes have led to an
increase in laser cavity gain from 0.26% cm-1 to 0.30%
cm-1. New modeling with BLAZE-V shows that an iodine
pre-dissociator can have a dramatic impact upon gain and laser
performance. As understanding of the ElectricOIL system continues to
improve, the design of the laser systematically evolves.
Recent experiments have led to continued improvements in the hybrid Electric Oxygen-Iodine Laser (ElectricOIL) system that significantly increased the discharge performance, supersonic cavity gain, and laser power output. Experimental investigations of radio-frequency discharges in O 2 /He/NO mixtures in the pressure range of 10-50 Torr and power range of 0.1-2.0 kW have shown that O 2 (a 1 Δ) production is a strong function of geometry, pressure and diluent ratio. The goal of these investigations was maximization of both the yield and flow rate (power flux) of O 2 (a 1 Δ) in order to produce favorable conditions for subsequent gain and lasing in our ElectricOIL system. Numerous measurements of O 2 (a 1 Δ), oxygen atoms, and discharge excited states are made to characterize the discharge. Results with both molecular iodine injection and partially pre-dissociated iodine are presented. A gain of 0.17% cm -1 was measured with a corresponding outcoupled power of 12.3 W. Modeling with the BLAZE-IV model is in good agreement with data.
Advanced chemical iodine laser technology will logically include novel all gas phase generation techniques for an iodine energy donor and the injection of atomic rather than molecular iodine. Candidate methods are discussed for the creation of an all gas phase energy donor as well as for injecting atomic iodine. This research will lead directly to designs that will be fabricated and tested extensively with detailed diagnostics to evaluate the chosen design's performance attributes. Preliminary analysis and modeling of the ElectriCOIL system concept is presented. ElectriCOIL will reduce weight and simplify both military and commercial chemical iodine laser systems. Potential cost and weight savings are also envisioned as the massive quantities of liquid chemicals will be completely eliminated from the device operation.
This work is devoted to the experimental and theoretical study of rf frequency influence on the discharge structure and the O-2(a(1)Delta(g)) yield in a rf discharge in the tubes with HgO coating for removing atomic oxygen to avoid fast O-2(a(1)Delta(g)) quenching. Two series of experiments were carried in two discharge sets up: 1 - tube of large diameter of 14 mm, electrode length of 30 cm; 2 - tube of small diameter of 7 mm, electrode length of 10 cm. In the first series, the increase of rf frequency from 13.56 MHz to 81 MHz resulted in the singlet oxygen (SO) yield Y > 15% at such high oxygen pressure as 10 Torr. 2D self-consistent model was developed to simulate the rf discharges in gas flow in a wide rage of discharge parameters both with and without HgO coating. Results of the simulation agreed very well with the experimental data. It is shown that at the high rf frequency the discharge operates in a mode of the normal current density so that the energy absorbed by electrons from the rf field increases with the frequency. In the second series we scaled up the rf discharge on the pd parameter (p-pressure, d-tube diameter) to increase the oxygen pressure. The pd discharge scaling at the high rf frequency allowed to reach the O-2(a(1)Delta(g)) yield Y > 15% at oxygen pressure up to similar to 17 Torr. The effect of NO admixture on the O-2(a(1)Delta(g)) production has been studied in series 2 at rf frequency of 160 MHz. NO admixture (5 divided by 20%) results in the noticeable increase in the O-2(a(1)Delta(g)) yield in comparison with the discharge tube without HgO coating. It is shown that combination of O-2 + NO mixture with HgO coating of the discharge tube walls provides the most optimal O-2(a(1)Delta(g)) production with the efficiency up to 7-10 % and allows to reach the threshold yield in 15 % at oxygen pressure even above similar to 20 Torr.
The excitation of I() in the reactions of discharge-generated O2(a ) and O() with I2 has been investigated in a microwave discharge-flow reactor at 1.5 Torr and ∼ 350 K using a suite of optical absorption and emission diagnostics to detect O2(a ), O, I(), and I() with high sensitivity. For O2(a ) yields of 0.20–0.25 generated by the microwave discharge, positive gain on the I(→) transition at 1.315 μm was observed when O concentrations were reduced by reaction with added NO2. The results imply quenching mechanisms for I() which are much faster than direct collisional deactivation by O.
The paper presents results of a high-pressure, non-self-sustained crossed discharge–M = 3 supersonic laser cavity operation. A stable and diffuse pulser–sustainer discharge in O2–He flows is generated at pressures of up to P0 = 120 Torr and discharge powers of up to 2.1 kW. The reduced electric field in the dc sustainer discharge ranges from 0.6 × 10−16 to 1.2 × 10−16 V cm2. Singlet delta oxygen (SDO) yield in the discharge, up to 5.0–5.7% at the flow temperatures of 400-420 K, was inferred from the integrated intensity of the (0, 0) band of the O2(a 1Δ → X 3Σ) infrared emission spectra calibrated using a blackbody source. The yield increases with the discharge power and remains nearly independent of the O2 fraction in the mixture (in the 10–20% range). Static pressure and temperature measurements in the supersonic cavity show that a steady-state M = 3 flow in the cavity can be sustained for up to 20 s, at the flow temperature of T = 120 ± 15 K. The results suggest that the measured SDO yield exceeds the threshold yield at the cavity temperature by up to a factor of 2.5. PLIF iodine vapour visualization in the supersonic cavity, which showed the presence of large-scale structures, suggests the need to improve iodine vapour mixing with the main oxygen–helium flow.
An overview is presented of experimental and theoretical research in the field of physics and engineering of singlet delta oxygen (SDO) production in low-temperature plasma of various electric discharges. Attention is paid mainly to the SDO production with SDO yield adequate for the development of an electric discharge oxygen–iodine laser (DOIL). The review comprises a historical sketch describing the main experimental results on SDO physics in low-temperature plasma obtained since the first detection of SDO in electric discharge in the 1950s and the first attempt to launch a DOIL in the 1970s up to the mid-1980s when several research groups started their activity aimed at DOIL development, stimulated by success in the development of a chemical oxygen–iodine laser (COIL). A detailed analysis of theoretical and experimental research on SDO production in electric discharge from the mid-1980s to the present, when the first DOIL has been launched, is given. Different kinetic models of oxygen low-temperature plasma are compared with the model developed by the authors. The latter comprises electron kinetics based on the accompanying solution of the electron Boltzmann equation, plasma chemistry including reactions of excited molecules and numerous ion–molecular reactions, thermal energy balance and electric circuit equation. The experimental part of the overview is focused on the experimental methods of SDO detection including experiments on the measurements of the Einstein coefficient for SDO transition and experimental procedures of SDO production in self-sustained and non-self-sustained discharges and analysis of different plasma-chemical processes occurring in oxygen low-temperature plasma which brings limitation to the maximum SDO yield and to the lifetime of the SDO in an electric discharge and its afterglow. Quite recently obtained results on gain and output characteristics of DOIL and some projects aimed at the development of high-power DOIL are discussed.
Herein the authors report on the demonstration of an 87% enhancement in cw laser power on the 1315 nm transition of atomic iodine via a 100% increase in the resonator mode volume. O 2 ( a 1 Δ ) is produced by a single rf-excited electric discharge sustained in an O 2 – He – NO gas mixture flowing through a rectangular geometry, and I ( P 2 1 / 2 ) is then pumped using energy transferred from O 2 ( a Δ 1 ) . A total laser output power of 102.5 W was obtained using a Z-pass resonator configuration.
We describe several diode laser-based instruments that can detect
important species in chemical oxygen iodine lasers (COIL). Species
detected include: water vapor, atomic iodine, and ground state oxygen.
The sensors allow non-intrusive, real-time measurements from which one
can determine small signal gain and the singlet delta oxygen yield. The
water vapor concentrations can also be continuously monitored. The
sensitivities of the sensors are sufficient for all the conditions found
in typical COIL devices. The room temperature diode lasers are miniature
and fiber coupled. Data for all three species are presented.
Recent investigations of an electric oxygen-iodine laser system have shown that computational
modeling overpredicts the experimentally measured power output for similar gain conditions. This
discrepancy is potentially due to an unknown reaction that competes with the forward pumping of
I�2P1/2� by O2�a 1��. Measurements of gain recovery downstream of an operating laser cavity were
performed. Modeling of this experiment shows that reducing the forward pumping rate by an
effective factor of approximately 4 to simulate a competing mechanism results in the computational
modeling matching the experimental gain recovery measurements, and in improved agreement
between the measured and modeled laser power extraction.
This is an overview of the development of Chemical Oxygen-Iodine Laser (COIL) technology in the United States. Key technical developments will be reviewed, beginning in 1960 and culminating in 1977 with the first COIL lasing demonstration at the Air Force Weapons Laboratory (now the Phillips Laboratory). The discussion will then turn to subsonic laser development, supersonic lasing demonstration and efficiency improvements, and finishing with a brief discussion of some spin off COIL technologies. Particular emphasis will be placed on how the O2 (1(Delta) ) generator and O2-I2 mixing nozzle technologies evolved.
In this paper, we report on studies of a continuous-wave laser at 1315 nm on the I(2 P 1 2) I(2 P 3 2) transition of atomic iodine where the O 2 (1 1) used to pump the iodine was produced by a radio frequency excited electric discharge. The electric discharge was sustained in He–O 2 and Ar–O 2 gas mix-tures upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilib-rium of atomic iodine in favor of the I(2 P 1 2) state. The results of experimental studies for several different flow conditions, dis-charge arrangements, and mirror sets are presented. The highest laser output power obtained in these experiments was 520 mW in a stable cavity composed of two 99.995% reflective mirrors. Index Terms—Chemical oxygen–iodine laser (COIL), electric discharge oxygen–iodine laser, electriCOIL, radio frequency (RF) excitation of oxygen, singlet-delta oxygen.
Herein the authors report on the demonstration of gain and a continuous-wave laser on the 1315 nm transition of atomic iodine using the energy transferred to I(2P1/2) from O2(a1Δ) produced by a radio-frequency-excited electric discharge sustained in a dry air-He–NO gas mixture. Active oxygen and nitrogen species were observed downstream of the discharge region. Downstream of the discharge, cold gas injection was employed to raise the gas density and lower the temperature of the continuous gas flow. Gain of 0.0062% cm−1 was obtained and the laser output power was 32 mW in a supersonic flow cavity.
cw laser action was achieved on the 2P1/2→2P3/2 transition of the iodine atom by energy transfer from the 1Δ metastable state of O2. The excited oxygen was generated chemically by flowing chlorine gas through a basic solution of 90% H2O2. The effluent from the oxygen generator was mixed with molecular iodine at the entrance of a longitudinal flow laser cavity where the I2 was dissociated by a small amount of O2(1Σ) that was present in the flow due to energy pooling processes. The measured output power was greater than 4 mW.
Herein the authors report on the demonstration of a 50% enhancement in gain and 38% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine through the addition of a secondary discharge to predissociate the molecular iodine in an electric oxygen-iodine laser. In the primary discharge the O2(a 1Δ) is produced by a radio-frequency-excited electric discharge sustained in an O2–He–NO gas mixture, and I(2P1/2) is then pumped using energy transferred from O2(a 1Δ). A gain of 0.10% cm−1 was obtained and the total laser output power was 6.2 W.
Herein the authors report on the demonstration of a continuous-wave laser in subsonic flow on the 1315 nm transition of atomic iodine using the energy transferred to I() from O2(a ) produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in an O2–He–NO gas mixture. Downstream of the discharge, cold gas injection was employed to raise the gas density and lower the temperature of the continuous gas flow to shift the equilibrium of atomic iodine in favor of the I() state. The laser output power was 540 mW in a stable cavity with two 99.993% reflective mirrors.
Singlet delta oxygen (SDO) yield, small signal gain, and output power have been measured in a scaled electric discharge excited oxygen–iodine laser. Two different types of discharges have been used for SDO generation in O2–He–NO flows at pressures up to 90 Torr, crossed nanosecond pulser/dc sustainer discharge and capacitively coupled transverse RF discharge. The total flow rate through the laser cavity with a 10 cm gain path is approximately 0.5 mole s−1, with steady-state run time at a near-design Mach number of M = 2.9 of up to 5 s. The results demonstrate that SDO yields and flow temperatures obtained using the pulser-sustainer and the RF discharges are close. Gain and static temperature in the supersonic cavity remain nearly constant, γ = 0.10–0.12% cm−1 and T = 125–140 K, over the axial distance of approximately 10 cm. The highest gain measured is 0.122% cm−1 at T = 140 K. Positive gain measured in the supersonic inviscid core extends over approximately one half to one third of the cavity height, with absorption measured in the boundary layers near top and bottom walls of the cavity. Laser power has been measured using (i) two 99.9% mirrors on both sides of the resonator, 2.5 W, and (ii) 99.9% mirror on one side and 99% mirror on the other side, 3.1 W. Gain downstream of the resonator is moderately reduced during lasing (by up to 20–30%) and remains nearly independent of the axial distance, by up to 10 cm. This suggests that only a small fraction of power available for lasing is coupled out, and that additional power may be coupled in a second resonator. Preliminary laser power measurements using two transverse resonators operating at the same time (both using 99.9–99% mirror combinations) demonstrated lasing at both axial locations, with the total power of 3.8 W.
Chemical oxygen-iodine lasers are unique in their ability to generate high-power beams with near diffraction limited beam quality. The operating wavelength, 1.315 µm is readily transmitted by the atmosphere and compatible with fiber optics beam delivery systems. However, applications of the laser are severely limited by logistical problems associated with the complex chemistry used to power the device. Electrical or microwave discharge excitation of oxygen-iodine lasers offers an attractive alternative that eliminates the chemical power generation problems and has the possibility of closed-cycle operation. A discharge oxygen-iodine laser was first demonstrated in 2005. Since that time the power of the device has been improved by a factor of 400 and much has been learned concerning the physics and chemistry of the discharge driven system. Although our current understanding of the chemical kinetics is incomplete, parametric studies of laser performance show considerable promise for further scaling. This article reviews the basic principles of the discharge oxygen iodine laser, summarizes the most recent advances, and outlines some of the unresolved questions regarding the production and removal of excited species in the gas flow.
Chemical oxygen-iodine lasers (COIL) are attractive for diverse industrial applications because they are capable of high efficiency, high power operation, and because the 1.315 μ m wavelength can be transmitted through fiber optics and couples efficiently with most metals. Conventional COILs are pumped with O 2(1 Δ ) that is generated by reaction of Cl 2 in a basic H 2 O 2 solution. Current trends in pumping COILs involve producing the O 2(1 Δ ) in electric discharges, thereby circumventing the hazards, complexity, and weight associated with pumping and storing caustic liquids. In this work, we have investigated the scaling of O 2(1 Δ ) yields with specific energy deposition in He / O 2 mixtures in flowing radio frequency (rf) discharges at pressures of a few to tens of Torr using a global plasma kinetics model. We found that O 2(1 Δ ) yield increases nearly linearly with specific energy deposition in O 2 molecules up to a few eV per molecule, with yields peaking around 30% by 5–8 eV . Further increases in specific energy deposition serve only to increase O 2 dissociation and gas heating, thereby reducing the O 2(1 Δ ) yield. We also found that variations in peak yields at a given specific energy de-
position are caused by secondary effects resulting from dilution, pressure, and power level. We show that these secondary effects alter the O 2(1 Δ ) yield by shifting the O 2(1 Σ )/ O 2(1 Δ ) ratio.
In an electric discharge oxygen-iodine laser, laser action at 1315 nm on the I (2P1/2)→ I (2P3/2) transition of atomic iodine is obtained by a near resonant energy transfer from O 2(a 1Δ) which is produced using a low-pressure electric discharge. The discharge production of atomic oxygen, ozone, and other excited species adds higher levels of complexity to the postdischarge kinetics which are not encountered in a classic purely chemical O 2(a 1Δ) generation system. Mixing effects are also present. In this paper we present postdischarge modeling results obtained using a modified version of the BLAZE-II gas laser code. A 28 species, 105 reaction chemical kinetic reaction set for the postdischarge kinetics is presented. Calculations were performed to ascertain the impact of a two stream mixing mechanism on the numerical model and to study gain as a function of reactant mass flow rates. The calculations were compared with experimental data. Agreement with experimental data was improved with the addition of new kinetics and the mixing mechanism.
Laser action at 1315 nm on the I (2P1/2)→ I (2P3/2) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O 2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O 2(a1Δ) has motivated investigations into purely gas phase methods to produce O 2(a1Δ) using low-pressure electric discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315 nm transition of atomic iodine where the O 2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in a He / O 2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I (2P1/2) state. The laser output power was 220 mW in a stable cavity composed of two 99.99% reflective mirrors.
Laser action at 1315 nm on the I(2P1/2)→I(2P3/2) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O 2(a1Δ) , which is produced using wet-solution chemistry. The system difficulties of chemically producing O 2(a1Δ) has motivated investigations into gas phase methods to produce O 2(a1Δ) using low-pressure electric discharges. In this letter we report on positive gain on the 1315 nm transition of atomic iodine where the O 2(a1Δ) was produced in a flowing electric discharge. The electric discharge was followed by a continuously flowing supersonic cavity that was necessary to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I (2P1/2) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the measurements of gain.
Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics.
Palla received the M.S. degree in aerospace engineering with the University of Illinois at Urbana-Champaign He is currently a Senior Physicist with CU Aerospace
- D Andrew
Andrew D. Palla received the M.S. degree in aerospace engineering with the
University of Illinois at Urbana-Champaign, Urbana, in 2004.
He is currently a Senior Physicist with CU Aerospace, Champaign, IL.
Benavides is a Ph.D. student in aerospace engineering with the University of Illinois at Urbana-Champaign, Urbana, with an expected graduation date of May 2012. He is currently a Senior Engineer with CU Aerospace
- F Gabriel
Gabriel F. Benavides is a Ph.D. student in aerospace engineering with
the University of Illinois at Urbana-Champaign, Urbana, with an expected
graduation date of May 2012.
He is currently a Senior Engineer with CU Aerospace, Champaign, IL.
M'98–SM'07) received the Ph.D. degree in aerospace engineering with the University of Illinois at
- David L Carroll
David L. Carroll (M'98–SM'07) received the Ph.D. degree in aerospace
engineering with the University of Illinois at Urbana-Champaign, Urbana, in
1992.
Day received the M.S. degree in aerospace engineering with the University of Illinois at Urbana-Champaign
- T Michael
Michael T. Day received the M.S. degree in aerospace engineering with the
University of Illinois at Urbana-Champaign, Urbana, in 2011.
King received the M.S. degree in aerospace engineering with the University of Illinois at Urbana-Champaign, Urbana, in 1999. He is currently the Laboratory Manager and a Senior Engineer with CU Aerospace
- M Darren
Darren M. King received the M.S. degree in aerospace engineering with the
University of Illinois at Urbana-Champaign, Urbana, in 1999.
He is currently the Laboratory Manager and a Senior Engineer with CU
Aerospace, Champaign, IL.
Carroll is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and the current Chair of the AIAA Plasmadynamics and Lasers Technical Committee
- Dr
Dr. Carroll is a Fellow of the American Institute of Aeronautics and
Astronautics (AIAA) and the current Chair of the AIAA Plasmadynamics
and Lasers Technical Committee.
Zimmerman received the Ph.D. degree in aerospace engineering with the University of Illinois at Urbana-Champaign He is currently a Staff Scientist with CU Aerospace
- W Joseph
Joseph W. Zimmerman received the Ph.D. degree in aerospace engineering
with the University of Illinois at Urbana-Champaign, Urbana, in 2010.
He is currently a Staff Scientist with CU Aerospace, Champaign, IL.
He was a Professor and the Head of aerospace engineering with the University of Illinois at Urbana-Champaign, Urbana, from 1988 to 1999. He is currently a Professor Emeritus with the University of Illinois at Urbana- Champaign and the Chairman of CU Aerospace
- C Wayne
Wayne C. Solomon received the Ph.D. degree in chemistry with the University of Oregon, Eugene, in 1963.
He was a Professor and the Head of aerospace engineering with the
University of Illinois at Urbana-Champaign, Urbana, from 1988 to 1999. He
is currently a Professor Emeritus with the University of Illinois at Urbana-
Champaign and the Chairman of CU Aerospace, Champaign, IL.
Woodard is a Ph.D. student in aerospace engineering with the University of Illinois at Urbana-Champaign, Urbana, with an expected graduation date of
- S Brian
Brian S. Woodard is a Ph.D. student in aerospace engineering with the University of Illinois at Urbana-Champaign, Urbana, with an expected graduation
date of December 2011.
Observations of gain on the ${rm I}(^{2}!P_{1/2}rightarrow,^{2}!P_{3/2})$ transition by energy transfer from ${rm O}_{2}(a^{1}Delta_{g})$ generated by a microwave discharge in a subsonic-flow reactor
- W T Rawlins
- S Lee
- W J Kessler
- S J Davis