8 ITMP3 / 8éme conférence internationale de photoacoustique et photothermique
J. Phys. IV France 04 (1994) C7-781-C7-784
Effective noise reduction on pulsed laser excitation of modes in a high-Q photoacoustic resonatorA. Miklós1, 2, C. Brand3, A. Winkler3 and P. Hess3
1 Wolfmahdenstrasse 70, 70563 Stuttgart, Germany
2 Institute of Isotopes of the Hungarian Academy of Sciences, P.O. Box 77, 1525 Budapest, Hungary
3 Institute of Physical Chemistry, University of Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
An open photoacoustic detector system, consisting of a high Q cylindrical resonator (Q factor in N2 ≈ 800) and two adjoining variable acoustic filter systems, was tested for pulsed excitation of acoustical modes in a naphthalene/air gas mix by using a 308 nm excimer laser. The outside noise suppression and the signal-to-noise ratio were investigated in a normal laboratory environment in the flow-through mode. The acoustic and electric filter system combined with the averaging of the photoacoustic signal in the time domain suppresses the outside noise by 70 dB. In this case the signal-to-noise ratio was 76 dB.
© EDP Sciences 1994