Radiation gauge

Claim 1

A radiation gauge for measuring the weight per unit area of non-homogeneous, large dimension traveling sheet materials, like fiberglass, during manufacture, comprising a 14 to 30 KEV monoenergetic X-ray source, said X-ray source comprising a primary source of gamma ray emitting radioactive material, said primary material being shaped in the form of an elongated member, a target material shell spaced from and positioned about and substantially extending along the full length of said primary source and having one end spaced closer to one end of said primary source and its other end spaced further from said primary source to direct radiation toward the intended direction of emission, said target material being responsive to the primary radiation emanating from said primary material to fluoresce a secondary, substantially lower energy X-rays; an ionization chamber detector means spaced from said X-ray source and positioned to receive said secondary radiation after passing through said material, said ionization chamber containing Krypton gas and producing a substantial K-edge response; said target material and primary source being selected to produce fluorescence X-rays of an energy greater than and substantially close to the K-edge of said Krypton gas, and substantially removed from said primary source energy; a collimator means disposed between said X-ray source and said traveling sheet material and comprising a frame with passage walls forming apertures that permit said X-rays to pass thrOugh said apertures to said traveling sheet material and substantially absorbs the primary source radiation that impinge on said frame walls; signal processing means coupled to said detector means to provide a signal responsive primarily to the weight per unit area of said material.