Mechanism of pulse discharge production of iodine atoms from CF₃I molecules for a chemical oxygen–iodine laser

Abstract

The pulsed chemical oxygen–iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and charged species, electric circuit equation, gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are found by solving the electron Boltzmann equation, which is re-calculated in a course of computations when plasma parameters changed. The processes accounted for in the Boltzmann equation include excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron–ion recombination, electron–electron collisions, second-kind collisions and stepwise excitation of molecules. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. Results of numerical simulations are compared with experimental laser pulse waveforms. It is concluded that there is satisfactory agreement between theory and the experiment. The prevailing mechanism of iodine atom formation from the CF3I donor in a very complex kinetic system of the COIL medium under pulse discharge conditions, based on their detailed numerical modelling and by comparing these results both with experimental results of other authors and their own experiments, is established. The dominant iodine atom production mechanism for conditions under study is the electron-impact dissociation of CF3I molecules. It was proved that in the conditions of the experiment the secondary chemical reactions with O atoms play an insignificant role.

Production of iodine atoms by RF discharge decomposition of CF3I

“…The equation (6)This evaluation of the dissociation fraction does not include excited iodine atoms, which may be formed in the discharge and eventually reach the detection region. Because the ISD signal absorption peak is proportional to c I -2c I* , their presence will artificially decrease the dissociation fraction.…”

“…Thanks to its properties, CF 3 I is of interest for the pulsed chemical oxygen-iodine laser. Since first experiments using the pulsed discharge in the O 2 -CF 3 I mixture [5], a thorough investigation of this system brought many new findings about relevant kinetics problems [6]. Quite recently, another production mechanism involving excited rare-gas atoms was pointed out in case of CH 3 I [7,8]:…”

Development Prospect of Gas Insulation Based on Environmental Protection

“…Shanghai Jiao Tong University uses Boltzmann's equation to calculate and analyse the discharge parameters and insulation characteristics of the gas mixtures of CF 3 I and N 2 , CO 2 , He and so on and get the alternating current (AC) breakdown voltage in non-uniform electric field and slightly non-uniform electric field by testing [28,30]. Other researchers have measured partial discharge voltage and other insulation characteristics of the gas mixtures of CF 3 I [31,32]. The results show that CF 3 I has good electrical insulation characteristics, but the positive synergistic effect of the mixture of CF 3 I and normal buffering gas is not obvious, so that the Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment insulation characteristics of its gas mixtures are lower than SF 6 .…”

Dielectric characteristic of dichlorodifluoromethane (R12) gas and mixture with N 2 /air as an alternative to SF 6 gas

“…In [15] dry air, nitrogen and carbon dioxide were examined but analysis shows that these gases lesser withstood voltage and there was a significant increase in the size of equipment. In [12, 16–23] mixtures of or have been studied and investigation show that it has high boiling point and toxic for reproduction. Mixtures of with air and have been reviewed but research shows that it has high boiling point and high minimum operating temperature that for [14, 24].…”