Thermal diffusivity measurement of opaque materials at very high temperature by a modulated technique

A study of the thermal diffusivity measurement of opaque materials up to 2500 K by a modulated technique is presented. A cylindrical sample is symmetrically heated by two xenon are lamps. Modulation of one of the two lamps causes a periodic change in the sample temperature. An identification technique allows the thermal diffusivity of the material to be evaluated, based on the measurement of shifts between the temperature recorded on each planar side of the sample and the incident flow. An analytical approach makes it possible to establish an original identification model, the performance standards of which have been tested numerically. Then, an experimental setup tailored to this technique is described. Finally, thermal diffusivity measurements of graphites PT 2239 and POGO AXM 5Q1 between 1000 and 2500 K are presented. These results are critically reviewed by comparing them with measurements made at CETHIL under similar conditions (modulated method making use of a continuous-wave carbon-dioxide laser) and with data from the literature.