The singlet delta pooling rate has been measured in a chemical generator using gas phase laser Raman spectroscopy.
The measured rate is four times the currently accepted pooling rate constant. Our measurement also agrees with recent
ab initio rate calculations. This rate is one of the most important losses in the COIL laser and is believed responsible for
the production of vibrationally excited singlet delta oxygen. The vibrationally excited oxygen is thought to play a role in
the iodine dissociation process. A higher rate for this process will enhance dissociation at the cost of increased transport
losses. The previous experimental measurement was reviewed and an over simplification of the data analysis identified.
The NCl-I laser has been demonstrated using HN3 as a fuel with a combustor to produce chlorine atoms. In this
paper, we study the auto-decomposition of NCl3. This process could result in a new type of chemical laser that
would not need a combustor. We present the results of experiments designed to understand the basic physical
processes in this system. The NCl-I laser operates using only gaseous species, eliminating the need for
heterogeneous gas liquid reactions such as used in COIL chemical lasers. The lasing species is the same as in COIL,
simplifying the scaling process since many optical, tracking and propagation problems have been demonstrated in
the ABL program.
KEYWORDS: Chlorine, Absorption, Chemical species, Hydrogen, Chemical oxygen iodine lasers, Spectroscopy, Gas lasers, Iodine, Chemical lasers, Molecules
The NCl-I laser has been demonstrated using HN3 as a fuel with a combustor to produce chlorine atoms. In this paper, we discuss the possibility of producing NCl(a1Δ) from the auto-decomposition of NCl3. This would eliminate the requirement for a combustor. We present the results of experiments and kinetic modeling designed to understand the basic physical processes in this system. The NCl-I laser operates using only gaseous species, eliminating the need for heterogeneous gas liquid reactions such as used in COIL chemical lasers. The lasing species is the same as in COIL, simplifying the scaling process since many optical, tracking and propagation problems have been demonstrated in other
programs.
NCI3 is a more stable source of NCI(a) than HN3. The use of NCI3 as a source of NCI(a1Δ) for use in an iodine transfer laser has been modeled. The model suggests that gain can be obtained on the spin orbit transition of the iodine atom at 1.315µm in a purely chemical system. New quenching rates of NCI(a) by H2 and HCI show these species are not a serious problem in scaling the NCI3 system to high energy densities. The measurements of NCI(a) in our flow tube system are obscured at early times by CI2(B-X) radiation from the CI atom induced decomposition of NCI3. We have measured the contribution of this emission and find that the profile more closely matches the profile predicted by the kinetics code. We have measured the yield of CI atoms produced by a microwave discharge of 5% CI2 in He and find a dissociation fraction of about 25% in agreement with previous studies by Manke and Setser. The yield was measured by titrating the CI atoms with HI and observing the HCI(v=1) radiation. In studies of the production of NCI3, we have found that the yield of NCI3 is independent of the gas side mass transfer conditions. Our current reactor produces an NCI3 yield of about 20% relative to CI2. Since the production of higher flows of NCI3 is important for a laser experiment, we present some ideas for scaling NCI3 to higher flow rates. The use of NCI3 as a source of NCI(a1Δ) for use in an iodine transfer laser has been modeled. The model suggests that gain can be obtained on the spin orbit transition of the iodine atom at 1.315µm in a purely chemical system. The experimental data obtained to this point supports the model predictions.
The reactions of NCl3 have been studied with the aim of assessing the potential for an NCl3 fueled NCl(a) - I transfer chemical laser. In this set of experiments we are looking at the chlorine atom initiated decomposition of NCl3 and it's subsequent reaction with hydrogen.
The NCl-I laser has been demonstrated using HN3 as a fuel. In this paper, we discuss the possibility of constructing a NCl(a1Δ)-I transfer laser using NCl3 as a fuel. Not only is NCl3 more stable, but also may eliminate the requirement for a combustor. We present kinetic modeling and some initial results of experiments designed to understand the basic physical processes in this system.
The oxygen-iodine laser was the first electronic transition chemical laser. It first lased 25 years ago at the Air Force Weapons Laboratory. The development started several years earlier and involved the support of many people in the laser community. I would like to describe the early thoughts, insights and even misconceptions that we had in the early days. I will also highlight the contributions of many of the people and organizations that contributed to the early development of the COIL laser.
A spontaneous Raman scattering system has been developed which can monitor the yield of a COIL singlet oxygen generator performance in real time. This approach permits one to directly measure [O2(a1(Delta) )] and [O2((Chi) 3(Sigma) )] simultaneously by monitoring their Raman spectra on the same ICCD array. This technique is reviewed and the major sources of error discussed and analyzed. The uncertainty in the Raman cross section limits the accuracy of the measurement technique. With the current uncertainty of the Raman cross section, this technique gives an accuracy of better than 2.5 percent in the yield measurement at 50 percent yield.
Over the last several years, Rocketdyne has conducted a number of experiments on advanced jet generators. A number of these experiments were described last year at this conference. In this paper, additional detail describing the experiments are presented and new analyses are included. The experiments show that the jet generator is operating in the kinetic limited regime. A nozzle power flux of almost 400 watt/cm2 was demonstrated at a 20 kW power level.
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.
Over the last several years, Rocketdyne has conducted a number of experiments on advanced jet generators. Both cross flow jet generator and counter flow jet generators have been tested. We have made laser power measurements at our Continuous Wave Chemical Laser Facility (CWLL) and at the Air Force Phillips Laboratory RADICL test facility. A test there resulted in a measured chemical efficiency of 29.6%. This is the highest efficiency reported for a supersonic oxygen-iodine chemical laser.
In this paper I will review work in the development of Singlet Delta Oxygen Generators. I start out with an historical background as several recent reviews were from different perspectives than mine. The basic chemistry and generator performance for chlorine-BHP production of O2(a1(Delta) g) is covered. Finally, I discuss how generator yield influences laser performance and some questions from recent work.
A mathematical model for the production of singlet delta oxygen from the reaction of a gas containing chlorine with the hydroperoxy ion in liquid basic hydrogen peroxide is reviewed. An exact solution for the Cl2 utilization, O2(1(Delta) ) yield, and efficiency of the generator is obtained in the well-stirred limit (WSL) for which the surface concentration of HO2- is constant. A universal set of performance curves is presented and the implications when assessing generator performance are discussed. When depletion of the surface concentration of HO2- is important, perturbation theory is used to obtain a solution for the generator's utilization, yield, and efficiency which is a generalization of the corresponding WSL solution. A criterion for the validity of the perturbation solution is obtained and it is shown that the performance of a rotogenerator plateaus not too far above the value of disk rotation rate predicted by this criterion. Finally an integral method is used to obtain a simple, but approximate, solution of the utilization-yield equations which applies over a wide range of operating conditions.
The rate of generation of O2(1(Delta) g) using the chlorine-basic hydrogen peroxide reaction is a key element to predict the performance of the chemical oxygen iodine laser. O2(1(Delta) g) carries the energy in the laser, thus it is one of the prime determinants of power in the flow. To predict the performance of O2(1(Delta) g) generators requires the prediction of the utilization of chlorine, the yield of excited oxygen, and the concentration of potential contaminants in the chemical exhaust of the generator. This paper is an extension of a previous paper on this same topic. The reader is also referred to a companion paper in this conference which discusses the details of O2(1(Delta) g) production and yield.
The rate of generation of O2(1(Delta) g) using the chlorine-basic hydrogen peroxide reaction is a key element to predict the performance of the chemical oxygen iodine laser. O2(1(Delta) g) carries the energy in the laser, thus is one of the prime determinants of power in the flow. To predict the performance of O2(1(Delta) g) generators requires the prediction of the utilization of chlorine, the yield of excited oxygen, and the concentration of potential contaminants in the chemical exhaust of the generator. In essence, this is a standard problem in two phase flow. This paper is in the spirit of a review and describes the author's approach to the analysis to O2(1(Delta) g) generators.
The generation of O2(1(Delta) g) using the chlorine--basic hydrogen peroxide reaction is the heart of the chemical oxygen iodine laser. When O2(1(Delta) g) is generated, almost two-thirds of the exothermicity of the reaction is dissipated as heat within the liquid solution. The impact of this heat release on the generation and transport of O2(1(Delta) g) is the subject of this study.
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