Backscatter flaw detection system

Claim 1

APPARATUS FOR THE DETECTION OF FLAWS IN A MATERIAL SPECIMEN COMPRISING: IRRADIATING MEANS, LOCATED ADJACENT SAID MATERIAL SPECIMEN, FOR SUBJECTING A SELECTED LOCALIZED ZONE IN SAID MATERIAL SPECIMEN TO A DIRECTIONALLY-INCIDENT COLLIMATED BEAM OF RADIATION OF KNOWN ENERGY LEVEL; SELECTIVE DETECTING MEANS, LOCATED ON THE SAME SIDE OF SAID MATERIAL SPECIMEN AS SAID IRRADIATING MEANS, AND SELECTIVELY POSITIONED FOR SELECTIVELY DETECTING CERTAIN SINGLY-SCATTERED BACKSCATTERED PHOTONS RESULTING FROM COMPTON INTERACTIONS INDUCED IN THE SELECTED LOCALIZED ZONE OF SAID MATERIAL SPECIMEN BY SAID INCIDENT BEAM OF RADIATION, THE SELECTIVELY DETECTED BACKSCATTERED PHOTONS BEING THOSE WHICH PRESENT A MAXIMUM SCATTERED INTENSITY TO SAID DETECTING MEANS ACCORDING TO THE DICTATES OF THE EQUATION I=KE-(UX+U1X1)O WHEREIN I IS THE SCATTERED PHOTON INTENSITY, U IS THE ABSORPTION COEFFIENENT IN THE MATERIAL SPECIMEN MEDIUM FOR THE INCIDENT RADIATION BEAM ENERGY LEVEL, X IS THE DISTANCE FOR THE INCIDENT RADIATION BEAM FROM THE SURFACE WHERE SID INCIDENT BEAM ENTERS SAID MATERIAL SPECIMEN TO THE LOCALIZED ZONE IN SAID MATERIAL SPECIMEN, U1, IS THE ABSORPTION COEFFICIENT IN THE MATERIAL SPECIMEN MEDIUM FOR THE ENERGY LEVEL OF THE BEAM OF BACKSCATTERED PHOTONS, X1, IS THE DISTANCE FROM THE LOCALIZED ZONE IN SAID MATERIAL SPECIMEN TO THE SURFACE LOCATION WHERE THE BEAM OF BACKSCATTERED PHOTONS EXITS FROM SAID MATERIAL SPECIMEN, O IS THE SCATTERING COEFFICIENT FOR THE GIVEN ANGLE OF SCATTERING AS DEFINED BY THE INTERSECTION OF SAID INCIDENT BEAM OF RADIATION AND SAID BEAM OF BACKSCATTERED PHOTONS, AND K IS A CONSTANT; TRANSDUCERS MEANS CONNECTED TO SAID SELECTIVE DETECTING MEANS, SAID TRANSDUCER MEANS RECEIVING AND CONVERTING THE SELECTIVELY-DETECTED BACKSCATTERED PHOTONS TO ELECTRICAL IMPULSES WHOSE RELATIVE AMPLITUDES ARE REPRESENTATIVE OF THE INDIVIDUAL ENERGY LEVELS OF THE SELECTIVELY-DETECTED BACKSCATTERED PHOTONS; COUNTING MEANSA, CONNECTED TO THE OUTPUT OF SAID TRANSDUCER MEANS, FOR COUNTING PER UNIT TIME THE TOTAL NUMBER OF THE PHOTON-DERIVED ELECTRICAL IMPULSES PRODUCED BY SAID TRANSDUCER MEANS IN RESPONSE TO THE SELECTIVELY-DETECTED BACKSCATTERED PHOTONS, A CHANGE IN THE COUNT RATE OF SAID PHOTON-DERIVED ELECTRICAL IMPULSES WHICH IS NOT ATTRIBUTABLE TO KNOWN CHANGES IN SAID MATERIAL SPECIMEN BEING INDICATIVE OF THE PRESENCE OF A FLAW IN THE SELECTED LOCALIZED ZONE OF SAID MATERIAL SPECIMEN; DEPTH-CHANGE COMPENSATING MEANS, LOCATED ON THE SAME SIDE OF SAID MATERIAL SPECIMEN AS SAID IRRADIATING MEANS, FOR VARYING THE OPERATIVE CAPACITY OF SAID SELECTIVE DETECTING MEANS, WHEREBY SAID DETECTING MEANS DETECT BACKSCATTERED PHOTONS OF THE SELECTED GROUP IN SUCH FASHION THAT THE LOSS IN SENSITIVITY OF SAID DETECTION APPARATUS WITH INCREASE IN DEPTH, IN SAID MATERIAL SPECIMEN, OF THE POINT OF INTEREST IS JUST OFFSET BY AN INCREASE IN THE SELECTED-PHOTON DETECTING CAPACITY OF SAID DETECTING MEANS.