Measurements of electrode temperature evolution by laser light reflection

The electrode temperature rise during the starting of an arc discharge lamp has been measured using the temperature-dependent reflection coefficient of He-Ne laser light from metal surfaces. Lock-in techniques permit temporal resolution of about 3 ms, which is adequate to resolve 60-Hz phenomena such as electrode heating during the ac cycle. Calibration curves obtained by pyrometric measurements of constant-current tungsten ribbon lamps were used to relate the observed signal during electrode heating to its temperature. The technique described affords a nonintrusive method for measuring transient electrode temperature in an optically clustered environment with an accuracy of about 20%.