Spatio-Temporal Temperature Measurement
in Liquid Metal of a Rotating System
Spatio-temporal temperature fluctuation measurements are carried out to investigate oscillatory convection of mercury melts induced by coupling of natural convection with the rotations of crystal disk and crucible in a Czochralski crystal growing configuration.
Thermocouple probes rotating together with the crystal disk and crucible are used in order to minimize adverse effects occurred by placing fixed objects in a rotating flow. Many thermocouples(28) are used to study the relationship among the outputs, especially their phase relations, on the basis of which one can deduce the overall convection pattern and flow structure. Two slip ring assemblies are integrated to provide rotating electrical contacts. Thermocouple signals measured are amplified by a factor of 2201 by a linear thermocouple-amplifier before passing the slipring, to maximize the ratio of signal to noise induced by a mechanical brush of the slip ring. Without rotation, a platinum resistance thermometer(Pt100) is used to measure the temperature of a reference junction which is embedded in an isothermal copper block. With the rotations of disk or crucible, an electronic thermometer with juction compensator is used. A high resolution(<0.02K) temperature measurement in a rotating liquid metal has been successfully accomplished.