Dual purpose pyrometer for temperature and solidification velocity measurement

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Abstract
A dual purpose pyrometer is described that allows both accurate radiance temperature measurement and fast temporal response. The system uses two silicon photodiodes with separate optical paths derived from a common spot on the sample. The optical bandwidths and response times of each detection circuit are tailored to the function of each radiometer. The radiance temperature of electromagnetically levitated metallic samples is measured over a narrow optical bandwidth with a high‐gain silicon detector. The velocity of solidification of undercooled melts can be deduced from the rise time of the second silicon detector which samples a broad optical bandwidth and has a fast response time. Results from experiments on the undercooling and solidification behavior of electromagnetically levitated pure nickel show that the solidification velocity approaches 17 m/s at high undercooling.