Gamma ray density probe utilizing a pair of gamma ray sources and a gamma ray detector

Claim 1

A gamma ray density probe utilizing a first collimated beam of gamma rays, a second collimated beam of gamma rays having the same energy as the gamma rays in said first collimated beam, a collimated gamma ray detector, a beam controlling means, a switching means, a first pulse storing means, a second pulse storing means, a ratio building means and an output means, said first collimated beam of gamma rays being emitted into a sample of unknown density from a first reference plane along at least one trajectory at an incident angle of Alpha with respect to said first reference plane, said second collimated beam of gamma rays being emitted into said sample of unknown density from a second reference plane along at least one trajectory at the same incident angle Alpha with respect to said second reference plane, said collimated gamma ray detector being located in a third reference plane and generating an output pulse whenever detecting gamma rays that are scattered from said first and said second collimated beams of gamma rays under an angle Beta towards said collimated gamma ray detaector and that are incident on said gamma ray detector at an incident angle of ( Beta - Alpha ) with respect to said third reference plane, said third reference plane being unequally spaced from said first reference plane and said second reference plane, said beam controlling means turning off said first collimated beam of gamma rays whenever said second collimated beam of gamma rays is turned on and vice versa, said switching means sensing the position of said beam controlling means and opening said first pulse storing means for storage of pulses from said collimated gamma ray detector whenever said first collimated beam of gamma rays is turned on and opening said second pulse storing means for storage of pulses from said collimated gamma ray detector whenever said second collimated beam of gamma rays is turned on, said ratio building means computing the ratio of the number of pulses stored in said first pulse storing means to the number of pulses stored in said second pulse storing means, said ratio being displayed by said output means and being interpreted in terms of the density of said sample of unknown density being irradiated by said first collimated beam of gamma rays and said second collimated beam of gamma rays, and said interpretation of density of said sample being independent of the presence of uniform layers of interfering materials located between said gamma ray density probe and said sample of unknown density.