Characteristics of Pulsated Oscillation of Supersonic-flow Chemical Oxygen-Iodine Laser

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A supersonic-flow chemical oxygen-iodine laser (S-COIL) is expected to have outstanding potential as a high-power laser source. Extremely strong pulse would be extracted from the S-COIL by utilizing Q-switch operation. In order to develop and optimize this pulse laser system, characteristics of the laser such as beam quality, power, time-dependence, so on, should be accurately evaluated. Thus, in this study, numerical method is developed for simulating the laser optics.The calculation code consists of two parts one is a code for the gas flow and chemical reactions, and the other is that for the optics. Because of the difference of characteristic times between the phenomena in these two parts, every 300-time-steps of the latter calculation is coupled with one-time-step of the former. In the former part, three-dimensional, compressible Navier-Stokes equations and a chemical kinetic model encompassing 21 chemical reactions and 12 chemical species are solved by means of full-implicit finit … More e difference method. The flow in the cavity is assumed to be of the downstream of the throat mixing system, which is shown in the previous paper [1]. In the latter part, a paraxial wave equation is introduced so as to describe the diffraction and interference of the beam. The paraxial wave equation is derived from the Maxwell equation by simplifying with two assumptions that the laser beam is of single frequency, and that the propagating direction of it is almost axial. Additionally, another calculation adopting geometric optics instead of wave optics is conducted in order to examine the effects of diffraction and interference.The results indicate that the time dependence of the beam power is qualitatively similar between the wave and geometric optics. The peak power reaches to the maximum value at 90 ns after the initiation of oscillation. The peak value for the wave optics is 9 % less than that for the geometric optics. The calculated spreading angle of the beam is shown to decrease: its value at 25,000 ns is 20 % less than that at 90 ns. This means the laser quality at the maximum power is slightly worse compared to that of continuous extraction. Less