Signal noise ratio improvement technique for bulk thermal diffusivity measurement

This paper presents an improvement of the classical flash technique that allows measuring the thermal diffusivity of highly diffusive materials without the need of blackbody coatings. The method consists in heating the front face of the sample using a periodic pulses sequence with suitable period and pulse duration. The rear face temperature is recorded simultaneously. An inverse approach is then used to estimate the thermal diffusivity. The underlying model is completely analytical and includes heat transfer and analog signal processing which has been specifically designed for this experiment. A sensitivity analysis and an experiment optimization are performed. Applied to an uncoated copper sample, this method appears to be reliable even in the case of very low optical emission/absorption. Theoretical expectations have been confirmed from experimental data obtained considering copper. Thermal diffusivity has been estimated with less than 4% on both the standard and absolute deviation.