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2D LIF diagnostics of a diamond depositing oxyacetylene flame

European Physical Society
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2D LIF DIAGNOSTICS OF A DIAMOND DEPOSITING OXYACETYLENE FLAME R. Klein-Douwel, J. Spaanjaars and J.J. ter Meulen Dept. of Molecular and Laser Physics, University of Nijmegen Toernooiveld, 6525 ED Nijmegen, The Netherlands Introduction Two-dimensional Laser Induced Fluorescence is used to determine molecular distributions in an oxyacetylene flame, used to deposit diamond on a molybdenum or natural diamond substrate. Possible growth species investigated thus far include C2 (1], CHand OH. Experiment A commercially available welding torch (orifice 1.6 mm 0) is mounted on a translation stage above a substrate holder, see figure 1. High purity oxygen and acetylene are used, where the flows and mixing ratio are controlled by mass flow controllers. A molybdenum substrate is positioned at 1 mm below the tip of the flame front. The substrate is cooled to 1000°C by a pulsed water vaporizer. Diamond is deposited in a slightly fuel rich flame [2], with growth rates up to 100 f.lm per hour. Figurl' 1: Experimental setup for LIF measurements in the diamond depositing flame The output of a Nd:YAG pumped dye laser is used at different wavelengths to detect St'Yio'ral molecular species in the flame. The laser beam is focused in the flame by means of two cylindrical lenses, resulting in a thin laser sheet. The fluorescence is c.ollected at right angl<'S with the laser beam, using a CCD camera equipped with an image intensifier. Emission of the flame itself is suppressed by gating the imag<' intensifier. Image processiug 306 i \ 1 l \ l hardware and software are used to allow for background subtraction. A spatial resolution of 20 p.m is obtained. In order to avoid saturation of the camera system, molecular distributions have to be measured off-resonant. C2 is excited at 438 nm and detected at 471 nm (Swan system) and OH is excited at 282 nm and detected at 308-312 nm or excited at 248 nm and detected at 298 nm (A-X). CHis excited at 393 nm (B-

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