Case for an Improved Effective-Atomic-Number for the Electronic Baggage Scanning Program

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Z{sub eff}, a parameter representing an 'effective atomic number' for a material, plays an important role in the Electronic Baggage Scanning Program (EBSP) to detect threats in dual-energy computed tomography (CT) baggage-scanning systems. We believe that Z{sub eff}, as defined and used on this program, does not provide the accurate representation of a material's x-ray absorption properties that is needed by the EBSP. We present the case for a new method that defines an effective atomic number for compounds and mixtures, which we refer to as Z{sub e}. Unlike Z{sub eff}, Z{sub e} is tied by definition to the x-ray ... continued below

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PDF-file: 20 pages; size: 0.7 Mbytes

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Smith, J A; Martz, H E & Kallman, J S April 5, 2011.

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Description

Z{sub eff}, a parameter representing an 'effective atomic number' for a material, plays an important role in the Electronic Baggage Scanning Program (EBSP) to detect threats in dual-energy computed tomography (CT) baggage-scanning systems. We believe that Z{sub eff}, as defined and used on this program, does not provide the accurate representation of a material's x-ray absorption properties that is needed by the EBSP. We present the case for a new method that defines an effective atomic number for compounds and mixtures, which we refer to as Z{sub e}. Unlike Z{sub eff}, Z{sub e} is tied by definition to the x-ray absorption properties of each specific material. Use of this alternative will provide a more accurate scale for calibrating Micro-CT and EDS systems against standard reference materials and will provide a more accurate physical characterization of the x-ray properties of materials evaluated on those systems. This document: (1) Describes the current usage of the Z{sub eff} parameter; (2) Details problems entailed in the use of the Z{sub eff} parameter; (3) Proposes a well-defined alternative - Z{sub e}; (4) Proposes and demonstrates an algorithm for optimally associating Z{sub e} with any specified compound or mixture; (5) Discusses issues that can impact the usefulness of an effective-Z model; and (6) Recommends that, in order that the chosen effective-Z parameter not materially impact the accuracy of data produced by the EBSP program, the use of Z{sub eff} be replaced by Z{sub e}.

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PDF-file: 20 pages; size: 0.7 Mbytes

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  • Report No.: LLNL-TR-520312
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/1033743 | External Link
  • Office of Scientific & Technical Information Report Number: 1033743
  • Archival Resource Key: ark:/67531/metadc847084

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  • April 5, 2011

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  • May 19, 2016, 3:16 p.m.

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  • Dec. 2, 2016, 9 p.m.

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Smith, J A; Martz, H E & Kallman, J S. Case for an Improved Effective-Atomic-Number for the Electronic Baggage Scanning Program, report, April 5, 2011; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc847084/: accessed September 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.