Heterogeneous iodine cluster formation has been identified as the responsible factor resulting in large iodine titration requirements for Boeing's first high Mach number nitrogen ejector nozzle. A solution employing geometrically produced aerodynamic heating in the flow was envisioned to break up these clusters. Horizontal and vertical wire arrays (cluster busters) placed downstream of the nozzle exit plane (NEP) have been shown to significantly reduce the optimal iodine titration and to greatly improve the power extraction efficiency of the Chemical Oxygen-Iodine Laser utilizing this first generation ejector nozzle.
A new Chemical Oxygen-Iodine Laser (COIL) has been developed and demonstrated at chlorine flow rates up to 1 gmol/s. The laser employs a cross flow jet oxygen generator operating with no diluent. The generator product flow enters the laser cavity at Mach 1 and is accelerated by mixing with 5 gmol/s, Mach 5 nitrogen diluent in an ejector nozzle array. The nitrogen also serves as the carrier for iodine. Vortex mixing is achieved through the use of mixing tabs at the nitrogen nozzle exit. Mixing approach design and analysis, including CFD analysis, led to the preferred nozzle configuration. The selected mixing enhancement design was tested in cold flow and the results are in good agreement with the CFD predictions. Good mixing was achieved within the desired cavity flow length of 20 cm and pressure recovery about 90 Torr was measured at the cavity exit. Finally, the design was incorporated into the laser and power extraction as high as 20 kw was measured at the best operating condition of 0.9 gmol/s. Stable resonator mode footprints showed desieable intensity profiles, which none of the sugar scoop profiles characteristic of the conventional COIL designs.
An advanced mixing nozzle concept has been developed for high chemical efficiency, high pressure recovery chemical oxygen-iodine laser applications. This concept incorporates the use of mixing tabs mounted at the nozzle exit plane for generating structured streamwise vorticity for mixing enhancement. The tab vortex generators produce strong streamwise vortices for mixing entrainment of highly compressible mixing layers. The optimal tab configuration, dimension, ramp angle relative to the flow direction, and tab spacing were determined by CFD analyses. The CFD computations show the entrainment and mixing produced by these mixing tabs are very efficient. The predicted mixing effectiveness of this nozzle configuration has been validated by experimental Pitot pressure scans of a three- blade nozzle hardware assembly.
The chemical oxygen-iodine laser (COIL) uses a reaction of gaseous chorine and aqueous solution of basic oxygen peroxide (BHP) to produce oxygen singlet delta molecules, O2(1(Delta) ). Quenching of O2(1(Delta) ) during its extraction from the BHP solution and quenching of excited atomic iodine I* by water vapor from the O2(1(Delta) ) production process are well-known parasitic effects in COIL. This paper shows that both of these effects can be significantly reduced by replacing the hydrogen 1H1 isotope atoms in BHP by the 1H2 isotope atoms. In addition to restoring laser power lost to parasitic quenching, use of basic deuterium peroxide (BDP) rather than BHP is expected to allow generation of O2(1(Delta) ) at elevated temperature. This approach promises to save refrigerant, reduce the risk of BDP freezing, and delay precipitation of salt form BDP solution. Methods for producing BDP are outlined.
A source flow gain model for optical extraction from the chemical oxygen-iodine laser medium is presented. In this model the gas dynamics of the reactive flow through the optical cavity, transverse to the optical axis, is described by the two-dimensional boundary-layer approximation to the full Navier-Stokes equations. The appropriate mass continuity, species, momentum, and energy conservation equations in cylindrical polar coordinates are presented and discussed. The gas kinetics are described by a reduced set of fourteen reactions among nine chemical species and includes pumping of the upper laser level by O2(1(Delta) ), deactivation by water and energy pooling with O2(1(Delta) ), and the Heidner molecular I2 dissociation mechanism. Stimulated emission on the 3 YLD 4 hyperfine transition of atomic iodine is described by a generalized version of the Zagidullian gain model which includes finite hyperfine relaxation of the 2P1/2 and 2P3/2 iodine sublevels, velocity cross-relaxation of the iodine atoms, and allows for incomplete I2 dissociation. The model is illustrated by application to a laboratory-sized device and the effects of the boundary layer upon the gas flow, I2 dissociation, O2(1(Delta) ) fraction, small signal gain, optical extraction, and the medium homogeneity are examined.
A detailed engineering model for chemical oxygen-iodine laser (COIL) performance modeling and design predictions has been developed. In this model, mixing between the primary oxygen flow and the secondary iodine injectant is treated using a two-stage/three-stream model based on the flow characteristics of the transverse injection mixing scheme. Iodine dissociation, excited state pumping and quenching are treated using the standard Phillips Laboratory COIL kinetics package. Stable resonator optical extraction is described by a rooftop geometric optics model. These models have been incorporated into the two-dimensional advanced cavity code for COIL (AC3). The validity of the mixing, kinetics, and optics models used in this code has been tested by comparing the predictions of the model with the iodine dissociation, laser small signal gain, and optical power data measured using the high pressure RotoRADICL device. Selected small signal gain and output power measured using the low pressure RotoCOIL were reproduced by the models. Modeling of the high efficiency RADICL data obtained with various nozzle throat heights using this model shows good agreement with power. The good agreement with the data obtained from various devices encompassing a broad range of experimental parameters lends credibility to this model.
A promising candidate for a visible-wavelength chemical laser is the NCl molecule in the b1(Sigma) electronic state, emitting at 665 nm. This state can be generated by purely chemical methods. The energy-pooling reaction, NCl(a1(Delta) ) + I*(P1/2) yields (b1(Sigma) ), is estimated to have a rate coefficient of 1 X 1011 cm3/sec from a steady-state approximation. Experiments using a high speed flowtube have shown that NCl(a1(Delta) ) is generated in high yield via the reaction of HN3 with chlorine atoms. The measured yield is 65%. Preliminary measurements of gain were initiated employing the cavity ring-down technique. These experiments indicate that gain may be present under the operating conditions used. Confirmatory experiments are in progress.
Excited iodine atoms I(2P1/2) are created when ICl is injected into a stream of NCl(a1(Delta) ). A population inversion between the I(2P1/2) and I(2P3/2) states of atomic iodine was observed using an optical double-resonance technique.
KEYWORDS: Fluorine, Argon, Hydrogen fluoride lasers, Molecules, Industrial chemicals, Molecular lasers, Excimers, Chemical reactions, High power lasers, Gas lasers
XeF(B) has been observed in the reaction of SiH4 + 2 + XeF2. dependence of XeF(B) emission intensity on [XeF2], [F2], [SiH4] and [Ar] has been measured. Possible mechanisims of XeF(B) production is discussed.
KEYWORDS: Chlorine, Chemical species, Energy transfer, Iodine, Resonance energy transfer, Gas lasers, High power lasers, Chemical oxygen iodine lasers, Molecular energy transfer, Molecular lasers
Emission from I(2P1/2) at 1.315 micron has been observed from the energy transfer from NCl(a1Δ) to I(2P3/2). The NCl(a1Δ) was produced by reacting excess Cl with HN3. The Cl and HN3 react to give N3 and HCl. The N3 then reacts with Cl to yield NCl(a1Δ) and N2. A rate constant for the quenching of NCl(a1Δ) by I(2 P 3/2) was measured to be at least 1 x 10-10 cm3/s. This near gas kinetic rate is interpreted as evidence of an efficient near resonance energy transfer process; NCl(a1Δ, v = 0) + I(2P3/2) - NCl(X3Σ, v = 2) + I(2P1/2).
A physical model of time, temperature, composition, and wavelength-dependent optical absorption behavior of e-beam pumped Ne/Xe/NF3(F2) plasmas is developed and discussed. A data correlation based on the progressive analysis of results pertaining to increasingly complex mixtures is developed. Comparisons of the derived model with medium absorption data are presented and discussed. Where useful, data relating to fluorescence efficiency and medium gain are used to further develop aspects of the model left obscure by the available data relating to medium absorption.
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