| 摘要 |
PURPOSE:To execute a measurement precisely, by instantaneously irradiating radiant rays to one surface of a cylindrical sample whose thickness is larger than the radius by 1.5 times or so, observing a temperature rise of the other surface, and deriving a time required for making its temperature rise attain a constant ratio. CONSTITUTION:On one end face of a cylindrical sample 1 whose radius and thickness are (a) and (l), respectively, a smaller aperture 2 than this face is provided so as to be opposed. In this state, laser light 3 which has passed through this aperture is irradiated to said sample surface, and its temperature thetal is observed by a thermocouple contact 4 attached to the surface of the opposite side. In case when an intensity distribution exists in radiant rays for irradiating the sample, if time t1/2 required for making the temperature thetal attain 1/2 of the maximum temperature thetam, and t1/2/tc are denoted as Kc, it is possible to set diffusivity of heat (alpha) of the sample to alpha=Kcl<2>/t1/2. Accordingly, when a ratio L of thickess (l) and the radius (a) of the sample is selected to >=1.5 times, the coefficient Kc does not depend on the intensity distribution of irradiated light, and the measurement can be executed precisely. |
