Theoretical estimation and experimental studies on gas dissociation in TEA CO2 laser for long term arc free operation

• Published in: Optics and laser technology 2013-11, Vol.52, p.57-64
• Main Authors: Kumar, Manoj, Biswas, A.K., Bhargav, Pankaj, Reghu, T., Sahu, Shashikiran, Pakhare, J.S., Bhagat, M.S., Kukreja, L.M.
• Format: Article
• Language: English
• Subjects: Boltzmann transport equation; Carbon dioxide lasers; Discharge; Energy of dissociation; Gas lifetime; Lasers; Mathematical analysis; Mathematical models; Optimum gas replenishment rate; Replenishment; TEA CO2 laser
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2013.04.006

Gas dissociation in a high energy, high repetition rate Transversely Excited Atmospheric (TEA) CO2 laser in both sealed-off and gas replenishment modes were studied for nitrogen lean gas mixture. A comprehensive theoretical model based on the Boltzmann transport equation and the discharge excitation circuit equations was adopted to calculate the amount of CO2 dissociated during a single discharge pulse. Theoretically it is shown that inclusion of superelastic collisions in the Boltzmann transport equation is necessary for precise estimation of dissociation per pulse, particularly at high discharge energy loadings and for nitrogen rich gas mixtures. Gas lifetime for repetitively pulsed operations was found experimentally by measuring the amount of CO formed when frequent arcing sets in under sealed off operation. Using this model, the optimum replenishment rate of CO2 either by gas purging and/or by catalytic regeneration needed for arc free long term operation of the laser was estimated. The measured saturation values of CO concentration in the laser chamber agreed well with the calculated values for various operating conditions. Arc free, long term repetitively pulsed operation of the laser was achieved in the gas replenishment mode with gas purging and/or catalytic regeneration. •Accurate estimation of gas lifetime of a TEA CO2 laser.•Importance of superelastic collisions for accurate estimation of CO2 dissociation rate.•Optimum purge rate and/or catalyst requirement for long term operation of TEA CO2 laser.