J. Phys. IV France 125 (2005) 39-41
System of pulsed photoacoustics based on a TEA CO2 laser applied to SF6-N2 mixturesV. Slezak1, A. Peuriot1 and G. Santiago2
1 Centro de Investigaciones en Láseres y Aplicaciones (CITEFA-CONICET), Juan Bautista de La Salle 4397 (1603), Villa Martelli, Buenos Aires, Argentina
2 Laboratorio Láser, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, (1063), Ciudad de Buenos Aires, Argentina
A transversal single-mode TEA CO2 laser, whose cavity design is a diffraction coupled resonator, tuned at the 10P(16) line, is used for photoacoustic detection of SF6 traces in N2. The acoustic cavity, resonant at a longitudinal mode, is designed on the basis of an electric analog model of a one-dimensional resonator. The acoustic signal from SF6-N2 and the signal from a laser energy detector enter simultaneously into a PC through its sound port. The photoacoustic signal, proportional to the average number of absorbed photons per molecule, is found to increase with the laser energy as a power of 0.5. The constant of the setup, previously measured from pulsed photoacoustics on NO2-N2 mixtures excited with the second harmonic of a Q-switched Nd:YAG laser, allows to quantitatively determine the SF6 absorption cross section as a function of the CO2 laser fluence. The calibration of this system is performed down to 150 ppbV of SF6 in N2 at atmospheric pressure for different values of laser energy.
© EDP Sciences 2005