DEVELOPMENT OF AC CALORIMETRIC METHOD FOR THERMAL-DIFFUSIVITY MEASUREMENT .5. MODULATED LASER-BEAM IRRADIATION

In an ac light-irradiation method for measuring thermal diffusivity al ong the length of the rectangular thin film sample, we developed a met hod which uses a modulated laser beam. The laser beam was swept with a high frequency so as to cover the width of the sample. Such a procedu re makes possible to obtain uniform ac thermal energy distribution in the direction perpendicular to the direction of ac temperature-wave pr opagation. Furthermore, it gives rise to a nonuniform ac thermal energ y distribution in the direction along the direction of ac temperature- wave propagation. It is theoretically proven that the latter inhomogen eity does not affect the determination of thermal diffusivity. This fa ct is verified by experiment.