Detection of sodium trace contamination in furnace atmospheres at 1000 °C

Free sodium atoms were detected by resonance fluorescence in an open contaminated quartz tube heated to 1000 °C. The quartz tube and furnace were similar to those used in semiconductor device processing. Fluorescence was excited by a cw dye laser tuned to the sodium D1 or D2 transition and directed along the axis of the furnace. Fluorescence from the sodium D2 line emitted in the axial direction was collected by a telescopic system and focused onto a photomultiplier tube. The estimated minimum detectable sodium density in the furnace is 5×105 atoms/cm3. No free sodium was detectable in a processing tube that had not been intentionally contaminated.