Physical Sciences Inc. is developing an advanced, compact LIDAR capable of continuous mapping of atmospheric extinction to provide environmental situational awareness for high energy laser weapon operations by the Navy. The LIDAR uses a MicroPulse LIDAR architecture and combines a solid state Nd:YLF laser operating at 1 micron with photon counting detectors and advanced aerosol retrieval algorithms. We report on the design of the engineering prototype and provide a summary of the system performance demonstrated during the Comprehensive Atmospheric Boundary Layer Extinction / Turbulence Refinement eXperiment conducted at the Shuttle Landing Facility at Kennedy Space Center in June, 2017.
The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkaliexciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms at number densities in excess of 1012 cm-3 in a continuous-wave electric discharge in flowing gas mixtures with helium diluent. This paper describes continuing investigations of the use of linear microwave micro-discharge arrays to generate metastable argon atoms, Ar (4s, 1s5) (Paschen notation), in flowing mixtures of Ar and He at atmospheric and reduced pressures, in optical pump-and-probe experiments for laser development. We describe initial experimental investigations of several key aspects of concepts for scaling to higher output powers. This includes initial data on the dependence of argon metastable production and optically pumped gain on micro-discharge gap size, pressure, and discharge power. We have observed clearly measureable gain at pressures down to 85 Torr. We have also developed an overlapping dual-array micro-discharge-flow configuration, to conduct detailed measurements of Ar(1s5) production and loss. Spatially resolved measurements of Ar(1s5) distributions in discharge-flow provide preliminary indications of 20-50 μs collisional lifetimes of argon metastable atoms after they exit the active microplasma. This information is relevant to modeling the recycling of Ar(1s5) in the optically pumped laser, and to the scaling architecture of the optically pumped system. The dual-discharge investigations demonstrate the potential for volume scaling of the active gain medium in a simple multi-discharge, flow-through configuration.
The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkali-exciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at atmospheric pressure. This paper describes initial investigations of the use of linear microwave micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure in optical pump-and-probe experiments for laser development. Power requirements to ignite and sustain the plasma at 1 atm are low, <30 W. We report on the laser excitation dynamics of argon metastables, Ar (4s, 1s5) (Paschen notation), generated in flowing mixtures of Ar and He at 1 atm. Tunable diode laser absorption measurements indicate Ar(1s5) concentrations near 3 × 1012 cm-3 at 1 atm. The metastables are optically pumped by absorption of a focused beam from a continuous-wave Ti:S laser, and spectrally selected fluorescence is observed with an InGaAs camera and an InGaAs array spectrometer. We observe the optical excitation of the 1s5→2p9 transition at 811.5 nm and the corresponding laser-induced fluorescence on the 2p10→1s5 transition at 912.3 nm; the 2p10 state is efficiently populated by collisional energy transfer from 2p9. Using tunable diode laser absorption/gain spectroscopy, we observe small-signal gains of ~1 cm-1 over a 1.9 cm path. We also observe stable, continuous-wave laser oscillation at 912.3 nm, with preliminary optical efficiency ~55%. These results are consistent with efficient collisional coupling within the Ar(4s) manifold.
Diode-pumped alkali laser (DPAL) technology offers a means of achieving high-energy gas laser output through optical pumping of the D-lines of Cs, Rb, and K. The exciplex effect, based on weak attractive forces between alkali atoms and polarizable rare gas atoms (Ar, Kr, Xe), provides an alternative approach via broadband excitation of exciplex precursors (XPAL). In XPAL configurations, we have observed multi-quantum excitation within the alkali manifolds which result in infrared emission lines between 1 and 4 μm. The observed excited states include the 42FJ states of both Cs and Rb, which are well above the two-photon energy of the excitation laser in each case. We have observed fluorescence from multi-quantum states for excitation wavelengths throughout the exciplex absorption bands of Cs-Ar, Cs-Kr, and Cs-Xe. The intensity scaling is roughly first-order or less in both pump power and alkali concentration, suggesting a collisional energy pooling excitation mechanism. Collisional up-pumping appears to present a parasitic loss term for optically pumped atomic systems at high intensities, however there may also be excitation of other lasing transitions at infrared wavelengths.
In this paper we present experimental results on several features of optically excited alkali atoms. We describe small
signal gain measurements including spatially-resolved gain in atomic Cs. We discuss observations of numerous near- to
mid-IR emissions from states that are higher in energy than the pump beam photons. Finally we outline a measurement
scheme to determine the threshold pump intensities for two types of optically excited alkali lasers.
The chemistry of electric discharge driven oxygen iodine lasers (EOIL) has long been believed to have O2(a1▵g) as the
sole energy carrier for excitation of the lasing state I(2P1/2), and O(3P) as the primary quencher of this state. In many sets
of experimental measurements over a wide range of conditions, we have observed persistent evidence to the contrary. In
this paper, we examine comparisons of kinetics analysis and model predictions to experimental results from a supersonic
EOIL research reactor. This analysis leads to identification of important additional production and loss terms for the
lasing species, I(2P1/2), in the EOIL reaction mechanism. These mechanisms are also relevant to the catalytically
enhanced EOIL excitation mechanism. Exploitation of this chemistry can lead to substantial increases in gain and power
extraction efficiency in larger-scale EOIL systems. The analysis points to a significantly higher level of understanding of
this energetic chemical system, which can support application of advanced concepts in power scaling investigations.
In this paper we describe a platform for small signal gain measurements for alkali atom laser systems based on the
DPAL excitation method. We present initial results that clearly show the transition from absorption on the alkali atom D1
lines in Cs and Rb to optical transparency and positive gain. The achievement of optical gain is critically dependent upon
alkali cell conditions and collision partners. We also present the first spatially resolved gain measurements in a DPAL
system. The small signal gain methods described will be valuable tools for power scaling of these laser systems.
KEYWORDS: Oxygen, NOx, Data modeling, Chemistry, Chemical analysis, Microwave radiation, Absorption, iodine lasers, Chemical oxygen iodine lasers, Temperature metrology
The chemistry of electric discharge driven oxygen iodine lasers (EOIL) has long been believed to have O2(a1▵g) as the
sole energy carrier for excitation of the lasing state I(2P1/2), and O(3P) as the primary quencher of this state. In many sets
of experimental measurements over a wide range of conditions, we have observed persistent evidence to the contrary. In
this paper, we review our experimental data base in both room-temperature discharge-flow measurements and EOIL
reactor results, in comparison to model predictions and kinetics analysis, to identify the missing production and loss
terms in the EOIL reaction mechanism. The analysis points to a significantly higher level of understanding of this
energetic chemical system, which can support advanced concepts in power scaling investigations.
We are investigating catalytically enhanced production of singlet oxygen, O2(a1▵g), observed by reaction of O2/He
discharge effluents over an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have
previously reported a two-fold increase in the O2(a) yields by this process, and corresponding enhancement of I(2P1/2)
excitation and small-signal gain upon injection of I2 and NO2. In this paper we review observed I* excitation behavior and
correlations of the catalytically generated O2(a) with atomic oxygen over a large range of discharge-flow conditions to develop
a conceptual reaction mechanism for the phenomena. We describe a first-generation catalytic module for the PSI supersonic
MIDJet/EOIL reactor, and tests with this module for catalyst coating deposition and enhancement of the small-signal gain
observed in the supersonic flow. The results present compelling evidence for catalytic production of vibrationally excited
O2(X,v) and its participation in the I* excitation process. The observed catalytic effects could significantly benefit the
development of high-power electrically driven oxygen-iodine laser systems.
In this paper we describe several diagnostics that we have developed to assist the development of high power gas
phase lasers including COIL, EOIL, and DPAL. For COIL we discuss systems that provide sensitive measurements
of O2(a), small signal gain, iodine dissociation, and temperature. These are key operational parameters within COIL,
and these diagnostics have been used world-wide to gain a better understanding of this laser system. Recently, we
have developed and integrated a similar suite of diagnostics for scaling the EOIL system and will provide examples
of current studies. We are also developing diagnostics for the emerging DPAL laser. These include monitors for
small signal gain that will provide both a more fundamental understanding of the kinetics of DPAL and valuable
data for advanced resonator design. We will stress the application of these diagnostics to realistic laser systems.
Scaling of Electric Oxygen-Iodine Laser (EOIL) systems to higher powers requires extension of electric discharge
powers into the kW range and beyond, with high efficiency and singlet oxygen yield. This paper describes the
implementation of a moderate-power (1 to 5 kW) microwave discharge at 30 to 70 Torr pressure in a supersonic
flow reactor designed for systematic investigations of the scaling of gain and lasing with power and flow conditions.
The 2450 MHz microwave discharge is confined near the flow axis by a swirl flow. The discharge effluent,
containing active species including O2(a1▵), O(3P), and O3, passes through a 2-D flow duct equipped with a
supersonic nozzle and cavity. I2 is injected upstream of the supersonic nozzle. The apparatus is water-cooled, and is
modular to permit a variety of inlet, nozzle, and optical configurations. A comprehensive suite of optical emission
and absorption diagnostics monitors the absolute concentrations of O2(a), O(3P), O3, I2, I(2P3/2), I(2P1/2), small-signal
gain, and temperature in both the subsonic and supersonic flow streams. The experimental results include numerous
observations of positive gain and lasing in supersonic flow, and the scaling of gain with a variety of flow and
reaction rate conditions. The results are compared with kinetics modeling predictions to highlight key discrepancies
as well as areas of agreement. The observed gains are generally lower than the predicted values, due in part to
chemical kinetics effects and also due to mixing limitations specific to the reagent injection design. We discuss in
detail the observed effects related to O-atom chemistry, and their import for scaling the gain to higher levels. We
also will present initial beam quality measurements.
We are investigating catalytically enhanced production of singlet oxygen, O2(a1▵g), observed by reaction of O2/He
discharge effluents on an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have previously
reported a two-fold increase in the O2(a) yields by this process, and corresponding enhancement of I(2P1/2) excitation and
small-signal gain upon injection of I2. In this paper we report further observations of the effects of elevated temperature up to
410 K, and correlations of the catalytically generated O2(a) with atomic oxygen over a large range of discharge-flow
conditions. We have applied a diffusion-limited reaction rate model to extrapolate the catalytic reaction rates to the highpressure,
fast-flow conditions of the subsonic plenum of a supersonic EOIL test reactor. Using the model and the flow reactor
results, we have designed and implemented a first-generation catalytic module for the PSI supersonic MIDJet/EOIL reactor.
We describe preliminary tests with this module for catalyst coating deposition and enhancement of the small-signal gain
observed in the supersonic flow. The observed catalytic effect could significantly benefit the development of high-power
electrically driven oxygen-iodine laser systems.
We describe a series of measurements of absorption and laser induced fluorescence on cells that contained cesium and
rubidium and a rare gas: He, Ar, Kr, or Xe. These studies showed strong blue wing absorption to the short wavelength
side of the alkali atom D2 lines due to collisionally formed Cs- or Rb-rare gas excimers. We also have observed an
efficient two photon excitation of higher lying states in Cs and Rb that produces both intense blue emission and IR
atomic emission in the 1.3 to 3.8 μm spectral region.
We describe a series of measurements of absorption and laser induced fluorescence using cells that contained cesium and
rubidium and krypton as a bath gas. These studies showed strong blue wing absorption to the short wavelength side of
the alkali atom D2 lines due to collisionally formed Cs-Kr or Rb-Kr excimers. These studies indicate that these species
may be appropriate candidates for optically excited Rb and Cs atomic lasers.
Enhanced production of singlet oxygen, O2(a1Δg), was observed by reaction of O2/He discharge effluents on an iodine
oxide film surface in a microwave discharge flow reactor at 320 K. We observed a two-fold increase in the O2(a) yields in
excess of discharge-generated amounts for non-catalytic conditions. The iodine oxide surface appears to catalyze the
heterogeneous reaction to form O2(a) with high collision efficiency. Injection of molecular iodine into the catalytically
enriched active-oxygen flow resulted in excitation of the I(2P1/2) state approaching optical transparency at 1315 nm. Addition
of NO2 resulted in positive small-signal gain in the 320 K subsonic flow. The observed catalytic effect could significantly
benefit the development of electrically driven oxygen-iodine laser systems.
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 both radio-frequency and microwave electric
discharges 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 was obtained and the laser output power was 32 mW
in a supersonic flow cavity.
Scaling of EOIL systems to higher powers requires extension of electric discharge powers into the kW range and
beyond with high efficiency and singlet oxygen yield. We have previously demonstrated a high-power microwave
discharge approach capable of generating singlet oxygen yields of ~25% at ~50 torr pressure and 1 kW power. This
paper describes the implementation of this method in a supersonic flow reactor designed for systematic investigations of
the scaling of gain and lasing with power and flow conditions. The 2450 MHz microwave discharge, 1 to 5 kW, is
confined near the flow axis by a swirl flow. The discharge effluent, containing active species including O2(a1Δg, b1Σg+),
O(3P), and O3, passes through a 2-D flow duct equipped with a supersonic nozzle and cavity. I2 is injected upstream of
the supersonic nozzle. The apparatus is water-cooled, and is modular to permit a variety of inlet, nozzle, and optical
configurations. A comprehensive suite of optical emission and absorption diagnostics is used to monitor the absolute
concentrations of O2(a), O2(b), O(3P), O3, I2, I(2P3/2), I(2P1/2), small-signal gain, and temperature in both the subsonic and
supersonic flow streams. We discuss initial measurements of singlet oxygen and I* excitation kinetics at 1 kW power.
Predictive modeling of the performance of EOIL laser systems must address the kinetics of the active oxygen flow,
including the production of O3 from recombination of O and O2, and the effects of NO as an additive to remove O and
promote O2(a) formation. This paper describes experimental measurements of the reaction kinetics for active-oxygen
flows generated by microwave discharge of O2/He mixtures at 3 to 10 torr. The concentrations of O2(a1Δ), O, and O3
were directly measured as functions of reaction time in a discharge-flow reactor. Both the O removal rate and the O3
production rate were observed to be significantly lower than expected from the widely accepted three-body
recombination mechanism for O3 production, indicating the existence of a previously unknown O3 dissociation reaction.
Addition of NO to the flow well downstream of the discharge resulted in readily detectable production of O2(a) in
addition to that generated by the discharge. The observed O2(a) production rates were remarkably insensitive to
variations in total pressure, O2 concentration, and NO concentration over the ranges investigated. The mechanism for
this O2(a) production remains to be identified, however it appears to involve a hitherto undetected, metastable, energetic
species produced in the active-oxygen flow.
The paper presents results of singlet delta oxygen yield (SDO) measurements in a high-pressure, non-self-sustained discharge and small signal gain measurements on the 1315 nm iodine atom transition in the M=3 supersonic cavity downstream of the discharge. The results demonstrate operation of a stable pulser-sustainer discharge in O2-He flows at pressures of up to 120 torr and discharge powers of up to 2.2 kW. The reduced electric field in the DC sustainer discharge ranges from 6 to 12 Td. SDO yield in the discharge is up to 5.0-5.7% at the discharge temperatures of 400-420 K. The results suggest that SDO yield exceeds the gain threshold yield at the M=3 cavity temperature by up to a factor of three, which is confirmed by gain measurements. The highest gain measured in the supersonic cavity is 0.01%/cm.
The electric oxygen-iodine laser (EOIL) concept uses an electric discharge plasma to generate an effluent flow
containing singlet oxygen, O2(a1&Dgr;), and atomic oxygen, O, which react with I2 to excite the atomic iodine laser
transition at 1.315 &mgr;m. This chemically rich system has unique characteristics, whose understanding requires
systematic chemical kinetics investigation under carefully selected conditions to isolate the key reaction mechanisms.
We describe a series of reacting flow measurements on the reactions of discharge-excited active-O2 with I2, using a
comprehensive suite of optical emission and absorption diagnostics to monitor the absolute concentrations of O2(a1&Dgr;),
O2(b1summation), O(3P), O3, I2, I(2P3/2), I(2P1/2), small-signal gain, and temperature. These multispecies measurements
help to constrain the kinetics model of the system, and quantify the chemical loss mechanisms for I(2P1/2).
Microelectromechanical systems (MEMS) offer a promising approach for creating compact, efficient chemical oxygen
iodine lasers. In this paper we report the demonstration and characterization of a chip-scale, MEMS-based singlet
oxygen generator, or microSOG. The microSOG is a batch-fabricated silicon chip that is micromachined to form
reactant inlets and distribution system, an array of microstructured packed bed reaction channels to ensure good mixing
between the BHP and the chlorine, a gas-liquid separator that removes liquid from the output stream by capillary effects,
integrated heat exchangers to remove the excess heat of reaction, and product outlets. The microSOG has successfully
generated singlet delta oxygen, and the resulting singlet delta concentrations were measured in a quartz test cell
downstream of the chip using absolutely-calibrated near-infrared emission measurements made by an InGaAs array
spectrometer. A kinetics analysis was used to determine the concentration at the chip's outlet from the concentration at
the measurement point. Singlet delta yield at the outlet was determined to be about 81% at 150 Torr plenum pressure
with a 25 sccm flow of chlorine. The corresponding output flow carries about 1.4 W of power at the chip's outlet.
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(a1&Dgr;) 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(a1&Dgr;) generation system. The advanced model BLAZE-IV has been introduced in
order 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, O2(b1&Sgr;), and O atom, and gas temperature measurements, but is under-predicting the increase in
O2(a1&Dgr;) concentration resulting from the presence of NO in the discharge. A key conclusion is that the removal of
oxygen atoms by NOX species leads to a significant increase in O2(a1&Dgr;) 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.
Laser action 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(a1Δ) produced using a low-pressure electric discharge. In the electric discharge oxygen-iodine laser
(ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds significantly higher
levels of complexity to the post-discharge kinetics which are not encountered in a classic purely chemical O2 (a1Δ)
generation system. In this paper, the discharge species output for laser operating conditions are discussed. Spatial
measurements of O2(a1Δ) and O2 (b1Σ) are reported, and various methods for the determination of atomic oxygen levels
are discussed and compared. The injection of NOX into the system to benefit O2(a1Δ) production is investigated.
Generation of singlet oxygen metastables, O2(a1Δ), in an electric discharge plasma offers the potential for development of compact electric oxygen-iodine laser (EOIL) systems using a recyclable, all-gas-phase medium. The primary technical challenge for this concept is to develop a high-power, scalable electric discharge configuration that can produce high yields and flow rates of O2(a) to support I(2P1/2->2P3/2) lasing at high output power. This paper discusses the chemical kinetics of the generation of O2(a) and the excitation of I(2P1/2) in discharge-flow reactors using microwave discharges at low power, 40-120 W, and moderate power, 1-2 kW. The relatively high E/N of the microwave discharge, coupled with the dilution of O2 with Ar and/or He, leads to increased O2(a) production rates, resulting in O2(a) yields in the range 20-40%. At elevated power, the optimum O2(a) yield occurs at higher total flow rates, resulting in O2(a) flow rates as large as 1 mmole/s (~100 W of O2(a) in the flow) for 1 kW discharge power. We perform the reacting flow measurements using a comprehensive suite of optical emission and absorption diagnostics to monitor the absolute concentrations of O2(a), O2(b), O(3P), I2, I(2P3/2), I(2P1/2), small-signal gain, and temperature. These measurements constrain the kinetics model of the system, and reveal the existence of new chemical loss mechanisms related to atomic oxygen. The results for O2(a) production at 1 kW have intriguing implications for the scaling of EOIL systems to high power.
KEYWORDS: Chemical species, Iodine, Absorption, iodine lasers, Diagnostics, Chemistry, Chlorine, Semiconductor lasers, Chemical oxygen iodine lasers, Energy transfer
We discuss experimental results from spectroscopic and kinetic investigations of the reaction sequence starting with
NCI3 + H. Through a series of abstraction reactions, NCI (a1Δ) is produced. We have used sensitive optical emission
diagnostics and have observed both [NCI(a1Δ)]and [NCI(b1Σ)] produced by this reaction. Upon addition of HI to
the flow, the reaction of H + HI produced iodine atoms that were pumped to the excited I(2P1/2) state, and we
observed strong emission from the I atom 2P 1/2 -> 2P3/2 transition at 1.315 μm. With a tunable diode laser we probed
the I atom transition and observed significant transfer of population from ground state (2P3/2) to the excited state
(2P1/2) and have observed optical transparency within the iodine atom energy level manifold.
In this paper we discuss several sensitive diagnostics that have specifically developed for application to COIL and other iodine laser concepts such as AGIL and DOIL. We briefly cover the history of some important diagnostics including recently-developed diode laser sensors for a variety of parameters including: water vapor concentration, singlet oxygen yield, small signal gain, and translational temperature. We also discuss new developments and extensions of prior capabilities including: an ultra-sensitive diagnostic for I2 dissociation, a new monitor for singlet oxygen yield, and a novel diode laser-based imaging system for simultaneous, multipoint spatial distributions of species concentration and temperature. Finally, we mention how these diagnostics have bee successfully applied to the emerging DOIL technology.
In this paper we discuss the application of sensitive, non-intrusive diagnostic techniques to characterize species in the flow that are critical for chemical oxygen iodine laser (COIL) devices and the electric discharge oxygen iodine laser (DOIL) concept. The key diagnostics include chemiluminescence to detect O2(a,b) and I(2P1/2) and tunable diode laser absorption measurements of I* and temperature. We have characterized variations in O and O2(a) yields with discharge power and oxygen mole fraction. We observe O2(a) yields to increase dramatically with decreasing oxygen mole fraction. We also discuss the application of a novel imaging diagnostic to obtain 2-D images of species concentrations and temperature.
This paper presents results from investigations of mixing flowfields and optical gain profiles in HF chemical laser systems by infrared hyperspectral imaging. A chemiluminescent F + H2 reacting flowfield, produced in a high-fluence microwave-driven reactor, was imaged at a series of wavelengths, 2.6 to 2.9 μm, by a low-order, spectrally scanning Fabry-Perot interferometer mated to an infrared camera. The resulting hyperspectral data cubes define the spectral and spatial distributions of the emission. High-resolution images were processed to determine spatial distributions of the excited state concentrations of the product HF(v,J), as well as spatial distributions of small-signal gain on specific laser transitions. Additional high-resolution Fourier transform spectroscopy and spectral fitting analysis determined detailed excited state distributions in the reacting flowfield. The measurements confirm that our reactor generates inverted populations of HF(v,J).
This paper discusses methods, using non-intrusive diagnostic techniques, to characterize the detailed dynamics of I* gain and O2(a1Δ) yield on a laboratory microwave-discharge flow reactor, for conditions relevant to the electrically driven COIL concept. The key diagnostics include tunable diode laser absorption measurements of I* small-signal gain and temperature, high-precision absorption measurements of reactor I2 concentrations, absolute and relative spectral emission measurements of O2(a1Δ) and I* concentrations, and air-afterglgow determinations of O concentrations. We have characterized variations in O and O2(a) yields with discharge power and oxygen mole fraction. We observe O2(a) yields to increase dramatically with decreasing oxygen mole fraction. We have also demonstrated a spectral fitting analysis technique capable of quantifying the presence of vibrationally excited O2(a,v). This combined suite of diagnostics offers a comprehensive approach to performance characterization for electrically driven COIL concepts.
Preliminary measurements of the yield of O2(1Δ) as a function of power absorbed in an RF discharge are presented. The yield is deduced from measurements of gain/absorption using the PSI Iodine Scan diagnostic coupled with a data reduction technique originally developed by PSI. A more formal presentation of the method of deducing the yield is provided. Atomic oxygen titration experiments are presented along with gain as a function of power input to the system.
We discuss a non-intrusive diagnostic for mixing, species concentration, and optical gain for HF chemical lasers. The instrument is based on hyperspectral imaging using a low order Fabry-Perot interferometer. The basic theory behind this technology is described and several applications to a chemically reacting flowfield are presented.
12 Recent advances in mid-IR semiconductor laser technology based on intersubband transitions in InGaAs quantum wells promise a dramatic impact on tunable diode laser-based sensors for trace gases. This paper reports recent progress toward this realization of room-temperature laser-based sensors for combustion-generated pollutants such as NOx and SOx. Laboratory measurements of SO2 at 8.6 micrometers are presented with detection limits on the order of 1 ppm. Extensions of these approaches for higher sensitivity measurements in exhaust gas conditions are described, as well as measurements of SO3.
KEYWORDS: Particles, Sensors, Contamination, Radiometry, Atmospheric particles, Interferometers, Radio optics, Space operations, Near field optics, Telescopes
The sensitive, high resolution CIRRIS-1A radiometers/interferometer provided a unique capability to probe the optical environment surrounding the shuttle on the STS 39 mission. Ground processing was carefully controlled to minimize the contamination levels. Early in the mission all surfaces were subjected to extended solar exposure. These efforts were successful in that most of the data showed no evidence of contamination effects. However, particulate contamination effects were occasionally observed. The range and size of discrete particles are extracted from the particle radiances, spectral distributions, and blur circles.
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