Instrumentation and Measurement Physics(DIMP)
Physique des instruments et mesures (DPIM)
Jun SHEN
National Research Council Canada
Photothermal beam deflection techniques applied to the non-destructive measurements of thermophysical properties
Photothermal beam deflection (PBD), namely optical beam deflection, is a remote (noncontact) technique, which is suitable for studying samples in a severe environment. In the transverse PBD (or mirage effect) spectrometry, a probe beam probes the gradient of the optical refractive index in the deflecting medium adjacent to a sample surface, resulting in the deflection of the probe beam. The gradient of the optical refractive index is induced by the temperature gradient from the sample surface to the medium, and the temperature rise in the sample is the result of the conversion of the absorbed electromagnetic excitation radiation into heat. The optical and thermophysical properties of the sample, therefore, can be measured by monitoring the frequency dependence (for frequency-modulated excitation) or the time dependence (for pulsed excitation) of the PD signal. In this presentation, different configurations of PBD are introduced, and the experimental results with these configurations are presented. Thermal effusivities of different materials are obtained using frequency-modulated excitation method, and thermal diffusivities are measured with our recently developed step excitation technique. Thermal conductivity and unit volume specific heat then can be deduced from thermal diffusivity and thermal effusivity. Considerations in designing these configurations and performing experiments are also discussed.