Abstract: The present invention is a method and apparatus for calculating the amount and composition of inorganic material in a sheet material. The apparatus of the present invention is capable of calculating the composition of all the additives at once without requiring multiple cycles. The apparatus uses a combination of two techniques, namely an X-ray fluorescence analysis and a preferential X-ray absorption analysis. X-ray fluorescence is measured by a thermoelectrically cooled solid state detector. The apparatus can measure more than three additives. Measurement of argon in the air is used for compensation of electronic drift. An empirical correction is used to compensate for mutual interaction between X-ray fluorescence radiation and clay or talc. The measurement is compensated for dust accumulation by fluorescing the dust.

Abstract: There is provided a method of measuring thermal diffusivity of solids and electronic lifetimes and defect properties of semiconductors useful for in-situ, non-destructive monitoring of engineered materials and electronic substrates. The method, termed photothermal rate window method, involves irradiating a sample with a repetitive square laser pulse of duration .tau..sub.p and period T.sub.0 and monitoring the temperature profile by measuring the photothermal signal emitted from the sample. The period T.sub.0 of the repetitive heating pulse is maintained constant and the pulse duration .tau..sub.p is varied in the range between 0 and T.sub.0 with the temperature measured at each value of .tau..sub.p. The method of measuring semiconductor recombination lifetimes involves irradiating a sample and scanning one of either the period T.sub.0 and the pulse duration .tau..sub.p of the repetitive laser pulse with the other held constant. The photothermal signal emitted from the surface is measured.