Chemical Oxygen-iodine Laser Research Articles

Pulsed Chemical Oxygen Iodine Lasers Excited by Pulse Gas Discharge with the Assistance of Surface Sliding Discharge Pre-ionization

Continuous-wave chemical oxygen-iodine lasers (COILs) can be operated in a pulsed operation mode to obtain a higher peak power. The key point is to obtain a uniform and stable glow discharge in the mixture of singlet delta oxygen and iodide. We propose using an electrode system with the assistance of surface sliding pre-ionization to solve the problem of the stable glow discharge with a large aperture. The pre-ionization unit is symmetrically fixed on the plane of the cathode surface. A uniform and stable glow discharge is obtained in a mixture of iodide (such as CH3I) and nitrogen at the specific deposition energy of 4.5 J/L, pressure of 1.99–3.32 kPa, aperture size of 11 cm × 10 cm. The electrode system is applied in a pulsed COIL. Laser energy up to 4.4 J is obtained and the specific energy output is 2 J/L.

Comparison of one- and three-dimensional computational fluid dynamics models of the supersonic chemical oxygen–iodine laser

A simple one-dimensional (1D) computational fluid dynamics (CFD) model of the chemical oxygen iodine laser (COIL) with supersonic mixing is compared with three-dimensional (3D) CFD models and with experimental measurements of the COIL parameters. Dependence of the gain, iodine dissociation fraction and temperature at the resonator optical axis and of the output lasing power on the iodine flow rate predicted by the 1D model is in good agreement with that found using 3D models and experimental results. Hence the 1D model can be used instead of much more complicated 3D models for estimates of the working parameters of supersonic COILs.

Dissociation of molecular iodine in RF discharge for oxygen-iodine lasers

The dissociation of molecular iodine in 40 MHz-RF discharge was studied experimentally. This generation of atomic iodine is aimed at use in oxygen-iodine lasers. The discharge was ignited in a mixture of I2 + buffer gas fast-flowing through the cylindrical chamber and the discharge products were injected into a supersonic flow of nitrogen. The atomic iodine number density was measured in a low-pressure cavity after mixing with nitrogen and the dissociation fraction was calculated related to the input I2 flow rate. The dissociation fraction of 46.2% was achieved at 0.22 mmol/s of I2 and 7 mmol/s of Ar and RF power of 500 W. Argon and helium were used as a buffer gas; discharge stability and dissociation efficiency were better with argon. At the I2 flow rate corresponding to the operation of a 1 kW chemical oxygen-iodine laser, the dissociation fraction was about 20%. The dissociation efficiency (the fraction of absorbed energy used for the dissociation) significantly decreased with increasing in the specific energy. At a reasonable I2 flow rate (0.32 mmol/s), the maximum achieved efficiency was 8.5% and the corresponding energy cost was 8.9 eV per dissociating of one I2 molecule. The input energy of more than 3 kJ per 1 mmol of I2 is needed for dissociating at least 50% of I2. The obtained dependencies on the gas flow rates infer a good chance for scaling-up of the tested RF discharge generator for the intended application.

Theoretical research of the influence of operation mode of chemical oxygen-iodine laser on its pulsing

One-dimensional pre-mixed model for a pulsed chemical oxygen-iodine laser is presented according to the reaction mechanism in chemical oxygen-iodine laser. The influences of gas temperature of 150-450 K and pressure of 660-2660 Pa on single pulse energy, pulse duration and peak power are studied. The internal reason of the influences of pressure and temperature on laser characteristics is analyzed. The results show that the higher laser peak power can be obtained in the case of gas temperature of 150 K and pressure of 1330 Pa than in the case of 400 K and 2660 Pa. Thus an efficient pulsed chemical oxygen-iodine laser is promising if the abundant atomic iodine is generated instantaneously. The approach to atomic iodine generation does not disturb the state of supersonic flow.

Efficient pulsed chemical oxygen-iodine laser with instantaneous generation of atomic iodine by volumetric discharge

A pulsed chemical oxygen-iodine laser (COIL) using atomic iodine generated by volumetric discharge of CH3I is developed and tested. COIL with a gain length of 60 cm is energized by a square pipe-array jet singlet oxygen generator with basic hydrogen peroxide pumping circulations and operated at subsonic gas flow. Maximum output energy of 4.3 J, pulse duration of 50 μs, specific energy extraction from the active medium of 2.0 J/L, and the maximum chemical efficiency of 12.5% are achieved at a chlorine flow rate of 55 mmole/s.

超音速化学氧碘激光器能量提取对流场影响的数值研究

超音速化学氧碘激光器能量提取对流场影响的数值研究

Scalable chemical oxygen — iodine laser

The problem of scaling chemical oxygen — iodine lasers (COILs) is discussed. The results of experimental study of a twisted-aerosol singlet oxygen generator meeting the COIL scalabilityrequirements are presented. The energy characteristics of a supersonic COIL with singlet oxygen and iodine mixing in parallel flows are also experimentally studied. The output power of ∼7.5 kW,corresponding to a specific power of 230 W cm-2, is achieved. The maximum chemical efficiency of the COIL is ∼30%.

A Singlet Oxygen Generator with Rapid Separation Process

Singlet oxygen generator is the heart of chemical oxygen iodine lasers and has been the focus of research for many years. In this paper, a novel singlet oxygen generator with rapid separation technology is briefly put forward. To ensure short residence time, the design of reaction and separation processes happening simultaneously in through-flow reactors is dumpy shaped. By means of computational fluid dynamics, the calculations indicate that the residence time of O2(1Δ) in the new structure is about 15ms and the new SOG has excellent anti-entrainment and defoaming separation performance. The analytical results show the new structure is a feasible and promising technology in singlet oxygen generation cases.

Study of Different Nozzle Configurations for Supersonic COIL System

Supersonic chemical oxygen iodine laser (SCOIL) hasrecently proved itscapabilities against projectile targets such as missiles and rockets in the tests performed with ABL system. It is primarily a chemical based gas laser system involving extensive gas dynamics for achieving lasing action. COIL (l= 1.315 mm) is conducive for both defenseand industrial applications and the beam is optical fibre compatible. One of the chief components of a SCOIL device is the supersonic nozzle system which not only produces the desired cavity conditions in terms of Mach number and cavity pressure but is also responsible for efficient mixing of lasing [I2 + N2] and pumping media [O2 (1Dg) + N2]. The supersonic nozzle to a large extent controls the pressure recovery potential of the laser system and thereby the system volume. The present study discusses the performance of three nozzle configurations viz, slit, advanced/ ejector and winglet nozzle. The comparisons have been made in terms.

A pressure recovery system for chemical oxygen-iodine laser based on an active diffuser

An open-type pressure recovery system (PRS) for chemical oxygen-iodine laser was designed and fabricated. As a first stage, an active diffuser was used in which the ejecting gas supply was organized through nozzles disposed around the channel periphery. The second stage was a supersonic ejector. Numerical simulation data for the viscous turbulent flow with heat release through the diffuser gas-dynamic channel, and also data obtained by testing the active diffuser in operation on a model facility equipped with a vacuum chamber, are reported. The obtained data were used to develop a full-scale setup with exhaust of laser gas into the atmosphere; this has allowed us to optimize the performance characteristics of the setup and substantially improve its mass-dimensional characteristics. Special attention was paid to parameter matching and synchronization of laser start with the operation of PRS components.

Role of N2 molecules in pulse discharge production of I atoms for a pulsed chemical oxygen–iodine laser

A pulsed electric discharge is the most effective means to turn chemical oxygen–iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF3I : N2 : O2(3X) : O2(a 1Δg) flowing out of a chemical singlet oxygen generator. A transverse pulsed discharge is realized at various iodide pressures. The model comprises a system of kinetic equations for neutral and charged species, the electric circuit equation, the gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are repeatedly re-calculated by the electron Boltzmann equation solver when the plasma parameters are changed. The processes accounted for in the Boltzmann equation include direct and stepwise excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron–ion recombination, electron–electron collisions and second-kind collisions. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. A conclusion is drawn about satisfactory agreement between the theory and the experiment.

Performance of a Multistream Injection Chemical Oxygen-Iodine Laser with Starlet Ejectors

A variant of an ejector-mixing nozzle for a chemical oxygen―iodine laser was experimentally tested with notched starlet ejectors. Cold-flow planar laser-induced fluorescence measurements indicated that the starlets provide faster mixing. Hot-flow testing demonstrated that the starlet design improved laser performance by 20―30% above the basic cylindrical ejector design. Furthermore, a conical ejector design with starlet notches was tested that resulted in approximately a 15 % improvement above the cylindrical design and has the potential for higher pressure recovery. Pressures in the singlet-oxygen generator were relatively constant with ejector flow rate, suggesting that existing high-efficiency singlet-oxygen generators can be used with this ejector nozzle configuration without sacrificing generator performance for pressure recovery potential.

Research on the Characteristics of Si-Based Reflector under the Action of Strong Laser

Based on the design principle of high reflective (HR) membrane of multilayer medium. The HR membrane appropriate for the chemical oxygen-iodine laser (COIL) with Si/SiO2 as high low refractive index materials, was designed on the silicon substrate, using TFCale3.4 simulation design software. We get the reflectivity of COIL over 99.999% at the output wavelength of 1315nm, above 99.2% at the harmonic of 632.8 nm in theory. The thermal deformation of Si-based reflector under the irradiation of Gaussian beam are calculated, using heat conduction equations and axial thermal deformation formula.

Mixing enhancement in a multi-stream injection nozzle

We present quantitative analysis of image sequences of multi-stream injection nozzle flows with several different injection geometries in an experiment simulating mixing in a chemical oxygen-iodine laser. To visualize mixing, image sequences were acquired with planar laser-induced fluorescence (PLIF) in iodine that was injected into the main flow. The injection nozzle consisted of a slot, ejector, and injector block, with rows of ejector and injector holes along the slot length. The ejector flow exits in an underexpanded state so that upon expanding it forces the slot and injector flows together to enhance mixing. For this study, the diameter and geometry of ejector holes were varied to assess their effect on mixing. Two configurations of ejector holes were used, each with two different diameters for a total of four cases with data collected at downstream stations. We carry out a quantitative mixing analysis for these configurations, using two methods to quantify the mixing. The first method considers the statistics of the PLIF image intensity histograms, which are bimodal for poorly-mixed flows and have a single peak in well-mixed flows. The second method quantifies the properties of the mixing interface. Our analysis shows that two injection schemes significantly enhance mixing by stretching the mixing interface.

Chemical oxygen-iodine laser: aerooptics and gas dynamics

We have investigated the interaction of regular and irregular structures — systems of shock waves, rarefaction waves, and turbulent layers — in a chemical oxygen-iodine laser.

基于故障树的氧碘化学激光器故障分析

基于故障树的氧碘化学激光器故障分析

超音速化学氧碘激光器内流动与光能提取耦合仿真

超音速化学氧碘激光器内流动与光能提取耦合仿真

Off-axis negative-branch unstable resonator in rectangular geometry

The application of an off-axis negative-branch unstable resonator to an active medium of rectangular geometry is examined. The presented unstable resonator consists of spherical mirrors and a scraper mirror. The adaptation to the rectangular cross section is performed by the scraper, which takes two different shapes. One shape resembles a rectangular bracket "[" and the other resembles the letter "L." The [ and L configurations correspond to a shift of the optical axis away from the center of the cross section, toward one of the edges or toward one of the corners, respectively. Both scraper setups are examined numerically and experimentally. Experiments are performed with a multikilowatt class chemical oxygen iodine laser. The active medium is characterized by a low amplification coefficient. Measured results of the intensity distribution in the far field and of the phase distribution in the near field are shown for both resonator configurations. Using the same resonator magnification, the setup with the L-shaped scraper has a lower output coupling and, therefore, a higher output power and a slightly higher beam divergence. The L-shaped scraper configuration is able to cover the gain medium completely.

Nonequilibrium population of the first vibrational level of O2(1Σ) molecules in O2 — O2(1Δ) — H2O gas flow at the output of chemical singlet-oxygen generator

The concentrations of electron-excited particles have been determined by measuring the absolute spectral irradiance in the range of 600 — 800 nm of O2 — O2(1Δ) — H2O gas mixture at the output of a chemical singlet-oxygen generator (SOG). A nonequilibrium population of the first vibrational level of O2(1Σ) molecules has been clearly observed and found to depend on the water vapour content. In correspondence with the results of these measurements and according to the analysis of kinetics processes in the O2 — O2(1Δ) — H2O mixture, the maximum number of vibrational quanta generated in the O2(1Δ) + O2(1Δ) → O2(1Σ) + O2(3Σ) reaction is 0.05 ± 0.03. It is concluded that the vibrational population of O2(1Δ) at the output of the SOG used in a chemical oxygen—iodine laser is close to thermal equilibrium value.

Chemical oxygen-iodine laser with external production of iodine atoms in CH3I/Ar dc glow discharge

A cw chemical oxygen-iodine laser (COIL) operating in a subsonic mode with a high water content of ∼15% and external production of iodine atoms in CH3I/Ar dc glow discharge has been demonstrated. A straightforward comparison of COIL performance for two cases—conventional, when I2 was injected in the singlet oxygen flow, and when iodine atoms produced externally together with other discharge products were injected—was made. In the latter case nearly four times increase in output power was observed, suggesting that the relaxation of the energy stored in the singlet oxygen slowed down substantially, when the laser operated using CH3I/Ar discharge products instead of iodine molecules.