Nonuniform heating effects on thermal diffusivity measurements by the laser-pulse method: Influence of detector position

Laser-pulse method is a well-known technique for measuring thermal diffusivity of solids and is based on several assumptions, i.e., adiabatic conditions, short laser-pulse length, temperature independence of thermal properties, and uniform heating of sample surface. However, very little has been published on the nonuniform heating effect that can limit the accuracy of measurements of several percent. In this paper the solution of heat equations under particular nonuniform conditions has been presented. Moreover, a heuristic model has been introduced in order to describe nonuniform heating effects arising under a general laser energy distribution. In both cases a good agreement with experimental results has been obtained.