System and process for measuring ash in paper

A system for determining the concentration of a mixture wherein the first component includes at least three materials that each have a mass absorption attenuation coefficient and K-edges, said system comprising:

• a) x-ray source means that simultaneously produces two beams of x-rays and directing the beams into the mixture, at least one beam having a spectrum of x-rays having a plurality of energies, the first beam including x-rays having an energy above the K-edges of at least two of the materials and the second beam including x-rays having an energy below the K-edges of the same two materials, wherein the energy distributions of the two beams are different and are such that, for each beam, the mass absorption coefficient for the same two materials is substantially equal, but different from the mass absorption coefficient for the third material;
• b) x-ray receiver means that simultaneously receives portions of said two beams which are transmitted through the mixture;
• and
• c) computing means for determining the concentration of the first at least three material component based upon the two directed beams and the simultaneously received portions of the two beams and not based upon any other x-ray beams.

A system for determining the composition of a component in a mixture, wherein the component includes variable proportions of at least first, second and third materials with each having a mass absorption coefficient, the system comprising:

• a) a first x-ray source of a first incident x-ray beam and a second x-ray source of a second incident x-ray beam for simultaneously directing the beams into the mixture, the first and second x-ray beams each having a different spectrum of x-rays and at least one beam having a plurality of energies, the beams being such that, for both the first and second beams, the mass absorption coefficient of the first material is substantially equal to the mass absorption coefficient of the second material but different from the mass absorption coefficient of the third material;
• detectors for detecting portions of the simultaneous incident first and second x-ray beams which are transmitted through the mixture from the first and second x-ray sources and for generating signals indicative of the intensities of the detected transmitted portions of the x-ray beams;
• and
• c) computing means operatively coupled to the detectors to receive the signals and to compute an amount of the third material in the at least three material component based upon the signals, and not based upon any other x-rays.