Effects of pressure ratio on population inversion in a DF chemical laser with concurrent lasing |
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Authors: | Jun Sung Park |
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Institution: | Division of Aerospace Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea |
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Abstract: | A numerical simulation is presented for investigating the effects of pressure ratio of D2 injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The chemical laser is generally used for the industrial process and manufacturing as well as the military weapon system, which requires high power characteristic of laser system rather than the others. The population inversion is absolutely needed to generate the laser beam and is non-equilibrium process. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high-power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, a fully conservative implicit method and a second order total variation diminishing (TVD) scheme are used with the finite-volume method (FVM). An 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two D2 injector pressure cases; 192 and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the D2 injection pressure is lower. But, the higher D2 injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of D2 injector increases, the maximum small signal gain in the v1-0 transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher. |
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Keywords: | DF chemical laser _method=retrieve& _eid=1-s2 0-S0022407304002596& _mathId=si31 gif& _pii=S0022407304002596& _issn=00224073& _acct=C000053510& _version=1& _userid=1524097& md5=004914a10088bbbfb764286c41977d95')" style="cursor:pointer D2 injection pressure" target="_blank">" alt="Click to view the MathML source" title="Click to view the MathML source">D2 injection pressure Population inversion Lasing |
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