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Chemical oxygen-iodine lasers (COILs) have promising applications due to their high efficiency and ease of scaling to multikilowatt powers. Recent research has focused on pumping the iodine with O2(1Δ) produced by electric discharges. In a previous work, a global model was used to develop reaction mechanisms and determine the specific energy deposition (eV/O2) required to obtain high O2(1Δ) yields for electric discharge COILs. Experiments have recently achieved positive laser gain and oscillation with these energy depositions and have highlighted the importance of axial expansion of the plasma in optimizing excitation of the O2(1Δ). In this work, the consequences of axial transport on O2(1Δ) yields have been computationally investigated in flowing He/O2 plasmas at a few Torrs using a one-dimensional plasma hydrodynamics and kinetics model. We show that the experimentally observed extension of the plasma glow upstream and downstream of the electrodes is due to electron diffusion and capacitive coupling of the radio-frequency power source. We also show that ≈50% higher O2(1Δ) yields can be achieved with a pulsed discharge combined with continuous-wave discharge. [ABSTRACT FROM AUTHOR]

In conventional chemical oxygen-iodine lasers (COIL) the 1.315 μm transition in atomic iodine is pumped by a sequence of reactions of I2 and I with O2(1Δ) which is generated using liquid chemistry. Ongoing studies are investigating means to produce the O2(1Δ) precursor with an electric discharge (eCOIL) to enable a totally gas phase system. Due to the thermodynamic and power loading requirements, the plasma in eCOIL systems is sustained in a flow of a rare-gas diluent and the O2. In previous investigations, the scaling of production of O2(1Δ) was investigated using global-kinetics and one-dimensional (1D) models. It was found that the production of O2(1Δ) scaled linearly with energy deposition for moderate loadings (a few eV/O2 molecule). In this paper, these previous investigations are extended to two-dimensions using a plasma hydrodynamics model. The goal of this investigation is to determine if multidimensional considerations affect energy scalings for production of O2(1Δ). We found that O2(1Δ) production generally does scale linearly with energy loading, however, the saturation of O2(1Δ) production occurs at lower-energy loadings than predicted with global and 1D models. This trend is a result of the more accurately depicted and more localized energy deposition afforded by the two-dimensional model, and emphasizes the need for volumetrically uniform power deposition to optimize O2(1Δ) production. [ABSTRACT FROM AUTHOR]

Chemical oxygen-iodine lasers (COIL) are attractive for diverse industrial applications because they are capable of high efficiency, high power operation, and because the 1.315 μm wavelength can be transmitted through fiber optics and couples efficiently with most metals. Conventional COILs are pumped with O2(1Δ) that is generated by reaction of Cl2 in a basic H2O2 solution. Current trends in pumping COILs involve producing the O2(1Δ) in electric discharges, thereby circumventing the hazards, complexity, and weight associated with pumping and storing caustic liquids. In this work, we have investigated the scaling of O2(1Δ) yields with specific energy deposition in He/O2 mixtures in flowing radio frequency (rf) discharges at pressures of a few to tens of Torr using a global plasma kinetics model. We found that O2(1Δ) yield increases nearly linearly with specific energy deposition in O2 molecules up to a few eV per molecule, with yields peaking around 30% by 5–8 eV. Further increases in specific energy deposition serve only to increase O2 dissociation and gas heating, thereby reducing the O2(1Δ) yield. We also found that variations in peak yields at a given specific energy deposition are caused by secondary effects resulting from dilution, pressure, and power level. We show that these secondary effects alter the O2(1Δ) yield by shifting the O2(1Σ)/O2(1Δ) ratio. [ABSTRACT FROM AUTHOR]

Abstract: Random packs of spheres have been used to model heterogeneous and porous material morphologies during simulations of physical processes such as burning of coal char, convective burning in porous explosives, and regression of solid rocket propellant. Sphere packs have also been used to predict thermo-mechanical properties, permeability, packing density, and dissolution characteristics of various materials. In this work, we have extended the Lubachevsky–Stillinger (LS) sphere packing algorithm to create polydisperse packs of non-spherical shapes for modeling heterogeneity in complex energetic materials such as HMX and pressed gun propellants. In the method, we represent the various particle shapes using level sets. The LS framework requires estimates of inter-particle collision times, and we predict these times by numerically solving a minimization problem. We have obtained results for dense random packs of various convex shapes such as cylinders, spherocylinders, and polyhedra, and we show results with these various particles packed together in a single pack to high packing fraction. [Copyright &y& Elsevier]

Laser action at 1315 nm on the I(2P1/2)→I(2P3/2) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure electric discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315 nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in a He/O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(2P1/2) state. The laser output power was 220 mW in a stable cavity composed of two 99.99% reflective mirrors. [ABSTRACT FROM AUTHOR]