RADIANCE TEMPERATURES (IN THE WAVELENGTH RANGE 519-906 NM) OF TUNGSTEN AT ITS MELTING-POINT BY A PULSE-HEATING TECHNIQUE

Radiance temperatures (at six wavelengths in the range 519-906 nm) of tungsten at its melting point were measured by a pulse-heating techniq ue. The method is based on rapid resistive self-heating of the specime n from room temperature to its melting point in less than 1 s; and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed six-wavelength pyrometer. Melting was manifested by a plateau in the radiance temperature versus time function for each wavelength. The melting-point radiance temperatures for a given speci men were determined by averaging the measured temperatures along the p lateau at each wavelength. The melting-point radiance temperatures for tungsten were determined by averaging the results at each wavelength for 10 specimens (standard deviation in the range 0.5-1.1 K, depending on the wavelength) as follows: 3319 K at 519 nm, 3236 K at 615 nm, 32 07 K at 652 nm, 3157 K at 707 nm, 3078 K at 808 nm, and 2995 K at 906 nm. Based on estimates of the random and systematic errors arising fro m pyrometry and specimen conditions, the total uncertainty in the repo rted values is about +/-7 K at 653 nm and +/-8 K at the other waveleng ths.