Two approaches for assessing photon path length distribution in pulp -: art. no. 59461D

Pulp consists of distinguishable particles, the refractive indices of which differ from the index of the employed medium, water. We are thus dealing with an optically scattering material. Particle distribution in pulp is nowadays a focus of interest. This parameter is related to the photon path length distribution (PPLD) determined by the inhomogeneity of the scatterer. In order to assess PPLD, we use two methods. In the first, the particle properties in pulp are estimated by means of a microscope. A model for Monte Carlo simulation is then built to obtain PPLD. In the second, the signal generated by a laser pulse passing the cuvette filled with water or pulp is detected with a streak camera and the assessment of PPLD accomplished by a deconvolution procedure. To obtain the particle distribution, the two methods may be used together, so that the streak-camera measurements give PPLD, and in the following simulation process the particle distribution is found, which corresponds to the determined PPLD. The number and diversity of the sample sets currently used do not fulfill the statistical requirements of the industry. Nevertheless, the results achieved encourage us to develop the methods further.