Chemical Oxygen-iodine Laser Research Articles

A New Method for Magnetic Gain Modulation of Chemical Oxygen Iodine Laser Based on Flat-Top Pulsed Magnetic Field

A New Method for Magnetic Gain Modulation of Chemical Oxygen Iodine Laser Based on Flat-Top Pulsed Magnetic Field

Open-Path Atmospheric Transmission of Diode-Pumped Alkali Lasers in Maritime and Desert Environments.

A tunable diode laser absorption spectroscopy (TDLAS) device has been developed to study long-path atmospheric transmission near diode pumped alkali laser (DPAL) emission wavelengths. By employing a single aperture and retro reflector in a mono-static configuration, the noise associated with atmospheric and platform jitter were reduced by a factor of ∼30 and the open-air path length was extended to 4.4 km and over a very broad spectral range, up to 120 cm-1. Water vapor absorption lines near the rubidium (Rb) and cesium (Cs) variants of the DPAL near 795 and 894 nm, oxygen lines near the potassium (K) DPAL near 770 nm, and water vapor absorption in the vicinity of the neodymium-doped yttrium aluminum garnet (Nd:YAG) laser 1.064 μm and chemical oxygen iodine laser (COIL) 1.3 μm lines were studied. The detection limit for path absorbance increases from ΔA = 0.0017 at 100 m path length to 0.085 for the 4.4 km path. Comparison with meteorological instruments for maritime and desert environments yields agreement for the 2.032 km path to within 1.5% for temperature, 4.5% for pressure, and 5.1% for concentration, while agreements for the 4.4 km path are within 1.4% for temperature, 7.7% for pressure, and 23.5% for concentration. An intra cavity output spectroscopy (ICOS) device was also used as a spectral reference to verify location of atmospheric lines. Implications of TDLAS collection system design on signal-to-noise (S/N) are discussed as well as the effect of path turbulence on baseline noise and inform the selection of the DPAL variant least affected by molecular absorption.

Uncertainty evaluation of data acquisition and analysis system relevant to infrared flowing medium laser

In flowing medium Chemical Oxygen Iodine Laser (COIL), Singlet oxygen is produced by the exothermic reaction of basic hydrogen peroxide solution and chlorine gas. It pumps the iodine and lasing process takes place by stimulated emission. Laser power is extracted using cavity. Development of customized data acquisition system is essential for measurements and analysis of both fundamental (temperature, pressure, level) as well as derived parameters (lasing medium concentration, flow rates of gases and laser power). The focus of the present paper is to dwell on uncertainty evaluation of a complex gas laser source in terms of ascertaining influences of primary/fundamental variables and corresponding derived parameters along with manner of uncertainty propagation. The study facilitates determining the variables with most significant impact on system performance, critical form point of view from optimal functioning of large-scale systems. This enables prediction of overall system uncertainty potentially extendable to other similar laser systems involving subsystems with mutual interdependencies together being distributed over a significantly large laboratory space. The relative combined uncertainty is computed to be 8.3%. The methodology shows significant potential for true decision-making and control of realistic gas laser source operation using developed 150 channel Data Acquisition and Analysis System (DAAS).

The Dynamics and Characteristics of the Pulsed Discharge in the Active Medium of a Pulsed Chemical Oxygen-Iodine Laser

In this article, a one-dimensional self-consistent hybrid model of fluid and kinetics is developed to simulate the pulsed discharge occurring in the active medium with a composition CF3I–O2–O2(a1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\bigtriangleup$ </tex-math></inline-formula> g)–He in a pulsed chemical oxygen-iodine laser (COIL). The iodine atom formation mechanism, the energy exchange between singlet delta oxygen and iodine atom, and the behaviors of various discharge products during the discharge and postdischarge are studied in detail. The dependences of the iodine atom density and energy cost of an iodine atom on the partial pressure ratio of the gas mixture are analyzed and discussed. It is shown that the main channel of iodine atom formation is the electron impact dissociation of CF3I rather than the ionization process. Chemical reaction processes have a small contribution to I atom production, especially the reaction processes involving oxygen. Keeping total pressure and oxygen partial pressure unchanged, there exists an optimum ratio of CF3I:He, at which the highest iodine atom density and the lowest energy cost are achieved. Under simulation conditions, I atom concentration decreases with increasing total operation pressure and oxygen pressure. At constant total pressure and oxygen pressure, when the content of singlet oxygen is lower than 40% of total oxygen pressure, the population inversion cannot be formed.

Numerical simulation of the magnetically gain-switched chemical oxygen-iodine laser

During the operation of the magnetically gain-switched chemical oxygen-iodine laser (MGS-COIL), the transition intensity of hyperfine transition line 2-2 can exceed that of line 3–4, which is the dominant line at zero magnetic field. For this reason, a simulation model including both 3–4 and 2-2 transition lines is necessary to describe the mode buildup process in MGS-COIL. In this paper, we assume that 3–4 and 2-2 transition lines simultaneously oscillate in laser cavity. The propagation of optical field is calculated based on FFT. The required frequency, rise time and residual field of the magnetic gain-switch for a high-performance MGS-COIL are analyzed based on simulation results.

Real Time Flow Control System for Precise Gas Feed in COIL

This paper reports development of a real time flow control system for precise, controlled and uniform gas feed to a flowing medium Chemical Oxygen Iodine Laser (COIL). The optimal operation of this prominent laser depends upon the desired supply of gas constituents such as nitrogen (N2), chlorine (Cl2) and iodine (I2) to achieve adequately mixed laser gas. The laser also demands real time variation of flow rates during gas constituent transitions in order to maintain stabilized pressures in critical subsystems. Diluent nitrogen utilized for singlet oxygen transport is termed as primary buffer gas and that for iodine transport is termed as secondary buffer gas (with main and bypass components). Also, nitrogen in precise flows is used for mirror blowing, nozzle curtain, cavity bleed and diffuser startup. A compact hybrid data acquisition system (Hybrid DAS) for precise flow control using LabVIEW 2014 platform has been developed. The supported flow ranges may vary from few mmole.s-1 to few hundred mmole.s-1. The estimated relative uncertainty in the largest gas component i.e. primary buffer gas feed is nearly 0.7%. The implementation of in-operation variation using flow ramp enables swift stabilization of singlet oxygen generator pressures critical for successful COIL operation. The performance of Hybrid DAS is at par with fully wired DAS providing the crucial benefit of remote field operation at distances of nearly 80m in line of sight and 35m with obstacles

Data Acquisition System for Chemical Iodine Generation Suitable for Flowing Medium Chemical Oxygen Iodine Laser

Development of infrared flowing medium lasers needs to be envisaged in a manner that practical aspects such as system compactness, short readiness time, low system size, weight and power are met to make them field deployable. In this context, the critical aspect of in-situ production of lasing species (Iodine) in Chemical Oxygen Iodine Lasers (COIL), one of the most potent flowing medium lasers, has been investigated. The paper dwells on chemical generation of iodine and its precise flow and parameter control by implementing a customised Data Acquisition System (DAS). Iodine is generated in a chemical reaction of Cuprous Iodide (CuI) with chlorine. This is achieved by precisely controlled flow of chlorine diluted with a carrier gas (N2 ) in a ratio of 1:2. DAS includes regulated gas feed, accurate thermal stabilisation, relevant diagnostics and implementation of necessary safety interlocks in a real time operation scenario for establishing the system efficacy and scalability. The studies have demonstrated chemically generated iodine flow rate of ~ 1.2 mmol.s-1 for Cl2 flow rate of ~3 mmol.s-1 all measured in real time using the developed DAS with a conversion efficiency of 80%. Developed I2 supply system has potential to deliver iodine on demand with required flow rates, measurement uncertainty of ~ 4.5 percent and advantages of smaller specific weight and size with reduced system readiness time and electrical power supply using DAS system with adequate safety interlocks.

Three dimensional transient analysis of bubble dynamics in centrifugal bubble singlet oxygen generator for scalable COIL

Chemical Oxygen Iodine Laser (COIL) is the shortest wavelength (1.315 μm) chemical laser employing singlet oxygen molecules as the pumping species and iodine atoms as lasing species. Singlet Oxygen Generator (SOG) is essentially the heart of this laser device which is basically a gas–liquid phase chemical reactor. SOG facilitates the reaction between a basic hydrogen peroxide solution (BHP, H2O2 + KOH) and chlorine gas to produce singlet oxygen molecules. Centrifugal Bubble Single Oxygen Generator (CBSOG) is a potential candidate for an alternative SOG with better operating conditions for high throughput and high power COIL systems. In CBSOG Chlorine gas is bubbled through a layer of BHP solution and the required reaction takes place at the gas–liquid interface of the formed bubbles under high speed rotation of the chamber for gravity independent operation. The performance of this device largely depends on the bubble formation characteristics and their traverse inside the BHP layer. The aim of this paper is to present the numerical analysis of the mechanics of bubble formation, detachment and movement in the BHP layer for different operating parameters as applicable to COIL. The determination of conditions for the transition from bubbling to the jetting regime at different centrifugal accelerations of high magnitude (G ∼ 204 g, 306 g & 387 g) with low liquid column thickness (∼6–8 mm) operating under low pressure (∼100 torr) is another point of focus. The Volume of Fluid (VOF) method has been used for the 3-D transient interface tracking between the phases. This paper also compares the simulation results for various gas flow rates and centrifugal accelerations with select experimental results reported elsewhere showing reasonably good agreement.

Development of the Long Duration Chemical Oxygen Iodine Laser

The development of Chemical Oxygen Iodine Laser (COIL) with a long duration is of important for the industry application of COIL. The aim of this research was to achieve a stable and longtime COIL operation. A systemic study of output power stability was performed from three aspects: influencing factors, solutions, and experimental verification. A 100s duration COIL in the power level of 5kW was firstly developed in our laboratory. The fluctuant range of power is about 5%, and the filling factor f (Imin/Imax) is about 0.4.

Nonadiabatic Electronic Energy Transfer in the Chemical Oxygen-Iodine Laser: Powered by Derivative Coupling or Spin-Orbit Coupling?

Derivative couplings near a conical intersection and spin-orbit couplings between different spin states are known to facilitate nonadiabatic transitions in molecular systems. Here, we investigate a prototypical electronic energy transfer process, I(2P3/2) + O2(a1Δg) → I(2P1/2) + O2(X3Σg-), which is of great importance for the chemical oxygen-iodine laser. To understand the nonadiabatic dynamics, this multistate process is investigated in full dimensionality with quantum wave packets using diabatic potential energy surfaces coupled by both derivative and spin-orbit couplings, all determined from first principles. A near quantitative agreement with structural, energetic, and kinetic measurements is achieved. Detailed analyses suggest that the nonadiabatic dynamics is largely controlled by derivative coupling near conical intersections, which leads to a small effective barrier and hence a slightly positive temperature dependence of the rate coefficient. The new results should extend our understanding of energy transfer, provide a quantitative basis for numerical simulations of the chemical oxygen-iodine laser, and have important implications in other electronic energy transfer processes.

Hybrid Data Acquisition and Analysis System for Flowing Medium Lasers

The medium gas lasers involves in-situ generation of the lasing medium, hence are associated with several complex processes including mixing of pumping and lasing species, energy exchange between the species, heat generation during reaction and its influence on the flow domain to list a few. Thus, the characterisation of lasing medium, condition of operation of individual critical subsystems and corresponding phenomenon thereof is essential in real time. It is here that a customised data acquisition and analysis system (DAAS) plays a key role. The paper dwells on the realisation of a customised hybrid DAAS with a master-slave architecture, which is portable and provides remote system operation. The noteworthy aspects of the developed DAAS include capability to handle close to 150 channels [64 analog input, 64 digital output, 5 analog output and 17 digital input] simultaneously with varied sampling rates requirement ranging from 100 samples/s to 200 k samples/s, modularity in design enabling scalability. Further, the efficacy of the developed DAAS has been tested by conducting several real time experiments with an existing chemical oxygen iodine laser source with a mass flow rate of 2.3 moles.s-1 both from close ranges and at line of sight remote distances of up to 80 m and nearly 35 m with obstacles.

Resonator to Laser Cavity Decoupling Interface for Chemical Oxygen Iodine Laser

In the present work, the conventional chemical oxygen iodine laser (COIL) source has been technologically upgraded and successfully tested after implementation of decoupling interface between laser cavity and resonator. In the technique, anti-reflection coated fused silica windows mounted in suitable mechanical assemblies are placed between resonator mirrors and laser cavity in such a way that the generated laser beam is out coupled through the resonator during the laser operation. The implemented decoupling assemblies isolate the caustic environment produced in low pressure laser cavity from that of resonator mirrors. Thus requirement of using isolation valves and cavity limbs between laser cavity and resonator as in conventional COIL source is eliminated. Such decoupling mechanism therefore effectively reduces the number of associated components as well as overall length of the laser source which in turn further reduces the overall weight of the laser making it suitable for use onto a mobile platform. Moreover the technique provides accrued benefits in terms of reduction in readiness time and checking of optical alignment of the laser source at will in practical operation scenarios.

Simulation experiment study on closed diluted gas cycle chemical oxygen iodine laser

The closed diluted gas cycle chemical oxygen iodine laser (CGC-COIL) was considered as a promising miniaturized laser; however, we havent read any experimental study reports till now. In this study, a simulation experiment setup composed of supersonic nozzle and screw vacuum pump was built, and it was used to study the feasibility and the operation stability of CGC-COIL by means of measuring the inlet and outlet aerodynamic parameters of the supersonic nozzle and screw vacuum pump. The simulation experiments firstly demonstrated the feasibility of this type of laser, and then confirmed the optimal stable operation condition of this type of laser by finding and explicating the phenomenon that a simulation laser cavity pressure inflection point will appear with the increase of the revolving speed of screw pump. The study provides an experimental evidence for CGC-COIL realization and a new technological approach for chemical oxygen iodine laser miniaturization.

Optimal design for the support structure of a cavity mirror in a chemical oxygen iodine laser resonator.

The dynamic characteristics of the cavity mirror support structure strongly influence the quality of the output beam. However, the contradiction between excellent dynamic performance and light weight make the design process challenging. To cope with the problems encountered in the original design of a chemical oxygen iodine laser system, this paper presents a two-dimensional adjustable support structure based on spherical constraints with large specific stiffness in the initial design phase. Subsequently, a two-level optimization strategy containing a macro design and a detailed design is adopted to optimize the initial structure. At the macro design stage, a two-step topology optimization procedure is introduced, in which the scale of the optimization model is dramatically reduced using the independent continuous mapping algorithm to improve the calculation speed in the first step, and the gray elements are eliminated using the bi-directional evolutionary structural optimization method to clearly obtain the optimal topology in the second step. This method is verified to overcome the defect of low efficiency, while still eliminating gray elements. At the detailed design stage, an adaptive surrogate model and the multi-objective design optimization method are employed to seek the best compromise between the lower weight and higher dynamic performance. The results from the application to the example of the cavity mirror support structure show that the mass is reduced by 41.8%, and the dynamic performance requirement is fulfilled.

Numerical investigation of the boundary layer separation in chemical oxygen iodine laser

Large eddy simulation is carried out to model the flow process in a supersonic chemical oxygen iodine laser. Unlike the common approaches relying on the tensor representation theory only, the model in the present work is an explicit anisotropy-resolving algebraic Subgrid-scale scalar flux formulation. With an accuracy in capturing the unsteady flow behaviours in the laser. Boundary layer separation initiated by the adverse pressure gradient is identified using Large Eddy Simulation. To quantify the influences of flow boundary layer on the laser performance, the fluid computations coupled with a physical optics loaded cavity model is developed. It has been found that boundary layer separation has a profound effect on the laser outputs due to the introduced shock waves. The F factor of the output beam decreases to 10% of the original one when the boundary transit into turbulence for the setup depicted in the paper. Because the pressure is always greater on the downstream of the boundary layer, there will always be a tendency of boundary separation in the laser. The results inspire designs of the laser to apply positive/passive control methods avoiding the boundary layer perturbation.

Performance comparison of supersonic ejectors with different motive gas injection schemes applicable for flowing medium gas laser

A class of flowing medium gas lasers with low generator pressures employ supersonic flows with low cavity pressure and are primarily categorized as high throughput systems capable of being scaled up to MW class. These include; Chemical Oxygen Iodine Laser (COIL) and Hydrogen (Deuterium) Fluoride (HF/DF). The practicability of such laser systems for various applications is enhanced by exhausting the effluents directly to ambient atmosphere. Consequently, ejector based pressure recovery forms a potent configuration for open cycle operation. Conventionally these gas laser systems require at least two ejector stages with low pressure stage being more critical, since it directly entrains the laser media, and the ensuing perturbation of cavity flow, if any, may affect laser operation. Hence, the choice of plausible motive gas injection schemes viz., peripheral or central is a fluid dynamic issue of interest, and a parametric experimental performance comparison would be beneficial. Thus, the focus is to experimentally characterize the effect of variation in motive gas supply pressure, entrainment ratio, back pressure conditions, nozzle injection position operated together with a COIL device and discern the reasons for the behavior.

A Chemosorption Vacuum Pump for a Chemical Oxygen Iodine Laser with CO2 Buffer Gases

We present the design and investigation of a novel chemosorption vacuum pump (CSVP) for discharging the exhaust gases of a chemical oxygen-iodine laser system diluted with carbon dioxide (CO2-COIL). The CSVP comprises two fixed-bed reactors separately filled with CO2/H2O and O2/I2/Cl2 adsorbents, which can efficiently chemically absorb the CO2-COIL exhaust gases at room or higher temperature. We consider the effects of the adsorbents in different specifications and fixed beds of various constructions on the adsorption performance of the CSVP. We develop and study the sealed CO2-COIL system with the CSVP. We achieve a stable operation with a cumulative duration time of 40 s for four runs and an average output power up to 2.0 kW at a Cl2 flow rate of ∼158 mmol/s and a CO2 flow rate of 132 mmol/s. The experimental results indicate that the COIL system with the CSVP performs similarly to a conventional COIL with a vacuum tank. Taking into account that the CSVP is free of vibration and noise, avoids air pollution, is easily operated, and has a short preparation time, we believe that the chemosorption vacuum pump is an excellent alternative pump system for a transportable COIL system.

Forecast of intense near- and mid-IR laser radiation propagation along slant atmospheric paths

The effectiveness of the use of intense radiation from different near- and mid-IR laser sources propagating along high-altitude slant optical paths is numerically estimated on the basis of the optical model of the Earth’s atmosphere developed by the authors. Different laser sources, including chemical oxygeniodine laser (COIL), chain chemical DF laser, and carbon-monoxide (CO) laser are considered with different optical weather conditions taking into account linear and nonlinear optical effects. A COIL source is shown to be the most preferable in terms of the total laser power transmitted along a path, because of weak atmospheric attenuation and minimal effects of nonlinear factors. In addition, this laser source shows the best performance in terms of the mean radiation intensity at a receiver. Among chemical multiwavelength lasers, DF lasers lead in terms of the power transfer function.

氧碘化学激光器腔镜表面缺陷的观察与分析

氧碘化学激光器腔镜表面缺陷的观察与分析

Experimental investigation and numerical simulation on continuous wave laser ablation of multilayer carbon fiber composite

Laser beam machining is one of the most widely used advanced processing techniques, which can be applied to compound materials. As a large number of photons are absorbed into the composite, the subsequent local heat storage, charring and potential delamination make the study for the effect of laser on complex materials become significant. In this paper, a carbon fiber epoxy composite laminated sheet is irradiated by continuous wave chemical oxygen iodine laser. The peak temperature of front surface, the temperature distribution of rear surface, and the appearance of ablation zone are presented. Further, based on the birth–death elements technique of finite element method, a three-dimensional model for simulating the transient temperature distribution and material removal has been developed under the same condition. The results reveal that the peak temperature of irradiated region ranges from 2800 K to 3100 K, and the center point shows a higher temperature rise rate than the surroundings in the irradiated zone. The measured data and predicted data are in a good consistency, which suggests that the numerical model is appropriate for simulating laser ablation of carbon fiber epoxy composites.