Backscatter flaw detection system

Claim 1

DETECTION APPARATUS, FOR THE DETECTION OF FLAWS IN A MATERIAL SPECIMEN AND INVOLVING A NON-DESTRUCTIVE TESTING TECHNIQUE REQUIRING ACCESS TO ONLY ONE SIDE OF THE MATERIAL SPECIMEN UNDER TEST, WHICH COMPRISES: IRRADIATING MEANS, ADAPTED TO BE OPERATIVELY LOCATED IN PROXIMITY OF SAID MATERIAL SPECIMEN, FOR SUBJECTING A SELECTED LOCALIZED THICKNESS ZONE IN SAID MATERIAL SPECIMEN TO INCIDENT RADIATION OF KNOWN ENERGY LEVEL; DETECTING-AND-CONVERTING MEANS, ADAPTED TO BE OPERATIVELY LOCATED ON THE SAME SIDE OF SAID MATERIAL SPECIMEN AS SAID IRRADIATING MEANS, FOR SELECTIVELY DETECTING AN EMERGENT ESSENTIALLY PARALLEL BEAM OF SINGLYSCATTERED BACK-SCATTERED PHOTONS OF A PREDETERMINED ENERGY LEVEL RESULTING FROM COMPTON INTERACTIONS INDUCED IN THE SELECTED LOCALIZED THICKNESS ZONE OF SAID MATERIAL SPECIMEN BY SAID MATERIAL-SPECIMEN-INCIDENT RADIATION AND FOR CONVERTING THE SELECTIVELY-DETECTED BACKSCATTERED PHOTONS TO CORRESPONDING ELECTRICAL PULSES, SAID DETECTING AND CONVERTING MEANS INCLUDING A SCINTILLATION CRYSTAL HAVING AN OPERATIVE SURFACE AREA AT LEAST AS WIDE AS SAID BEAM; COUNTING MEANS, OPERATIVELY CONNECTED TO THE OUTPUT OF SAID DETECTING-AND-CONVERTING MEANS, FOR COUNTING PER UNIT TIME THE TOTAL NUMBER OF PHOTON-DERIVED ELECTRICAL PULSES PRODUCED BY SAID DETECTING-AND-CONVERTING MEANS IN RESPONSE TO THE SELECTIVELY-DETECTED BACKSCATTERED PHOTONS, A CHANGE IN THE COUNT RATE OF SAID PHOTON-DERIVED ELECTRICAL PULSES WHICH IS NOT ATTRIBUTABLE TO KNOWN CHANGES IN SAID MATERIAL SPECIMEN BEING INDICATIVE OF FLAW PRESENCE IN THE SELECTED LOCALIZED ZONE OF SAID MATERIAL SPECIMEN; AND DEPTH COMPENSATING MEANS, ADAPTED TO BE OPERATIVELY LOCATED IN THE PATH OF THE AFOREMENTIONED SINGLYSCATTERED BACKSCATTERED PHOTONS ORIGINATING IN SAID SELECTED LOCALIZED THICKNESS ZONE AND OF THE PREDETERMINED ENERGYL LEVEL AND COMPENSATING ABSORPTIVELY ATTENUATING SAID SINGLY-SCATTERED BACKSCATTERED PHOTONS ORIGINATING IN SAID LOCALIZED ZONE AND OF THE PREDETERMINED ENERGY LEVEL BEFORE THEY ARE DETECTED BY SAID DETECTING-AND-CONVERTING MEANS, IN SUCH A FASHION THAT THE RESPECTIVE INDIVIDUAL PHOTONS OF SAID SINGLY-SCATTERED BACKSCATTERED PHOTONS ORIGINATED IN SAID SELECTED LOCALIZED ZONE AND OF THE PREDETERMINED ENERGY LEVEL, AND HEREINAFTER REFFERRED TO AS THE PHOTIONS-OF-INTEREST, ARE SUBJECTED BY SAID INTERCEPTING DEPTH COMPENSATING MEANS TO AN AMOUNT OF ABSORPTIVE ATTENUATION WHICH VARIES INVERSELY WITH THE LENGTH WITHIN SAID MATERIAL SPECIMEN, AS MEASURED FROM THE RADIATION-INCIDENT SIDE OF SAID MATERIAL SPECIMEN, OF THE POINT OF ORIGIN OF THE GIVEN PHOTON-OF-INTEREST IN A PREDETERMINED MANNER TO NULLIFY AN OTHERWISE PRESENT VARIATION IN TEST SENSTIVITY OF SAID DETECTION APPARATUS AS A FUNCTION OF SAID DEPTH WITHIN SAID MATERIAL SPECIMEN, THIS OTHERWISE-PRESENT TEST SENSITIVITY VARATION BEING CHARACTERIZED BY A LOSS IN TEST SENSITIVITY AS A DIRECT FUNCTION OF A AFOREMENTIONED DEPTH WITHIN SAID MATERIAL SPECIMEN OF THE GIVEN POINT-UNDER-CONSIDERATION WHICH IN THIS CONTEXT IS SYNONYMOUS WITH THE POINT OF ORIGIN OF THE INDIVIDUAL PHOTON-OF-INTEREST INVOLVED SAID DEPTH COMPENSATING MEANS COMPRISING: A WEDGE-SHAPED PHOTON-PASSING RADIATION-ATTENTUATING MEMBER OF A LENGTH TO LIE ATHWART THE PATH OF THE RADIATION BEAM DEFINED BY THE VARIOUS PHOTONS-OF-INTEREST AND IN INTERCEPTING POSITION WITH RESPECT TO SAID BEAM FORMED BY SAID PHOTONS-OF-INTEREST, THE THINNEST PORTION OF SAID WEDGE-SHAPED MEMBER BEING ADAPTED TO LIE IN THE PATH OF THOSE PHOTONS-OF-INTEREST WHICH ORIGINATE AT THE POINT OF GREATEST EXAMINATION DEPTH WITHIN SAID MATERIAL SPECIMEN, AS MEASURED FROM THE RADIATION-INCIDENT SURFACE OF SAID MATERIAL SPECIMEN, AND THE THICKEST PORTION OF SAID WEDGESHAPED MEMBER BEING ADAPTED TO LIE IN THE PATH OF THOSE PHOTONS-OF-INTEREST WHICH ORIGINATE AT THE POINT OF MINIMUM EXAMINATION DEPTH WITHIN SAID MATERIAL SPECIMEN, AS LIKEWISE MEASURED FROM THE RADIATIONINCIDENT SURFACE OF SAID MATERIAL SPECIMEN.