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X-ray Backscatter Detectors

X-ray Backscatter Detectors. By Mark Guseman. Topics. Source of x-rays Interaction with matter Detection and Processing Fooling the Detector Health Concerns. Source: Towe and Jacobs 1981. Source of X-Rays. Two guns used in airport detectors

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X-ray Backscatter Detectors

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  1. X-ray Backscatter Detectors By Mark Guseman

  2. Topics • Source of x-rays • Interaction with matter • Detection and Processing • Fooling the Detector • Health Concerns Source: Towe and Jacobs 1981

  3. Source of X-Rays • Two guns used in airport detectors • Low energy gun is equivalent to CAT scan source • High energy gun is stronger than used in a mammogram • Can either move the source or the object to be imaged Source: Kaufman and Carlson 2010

  4. Compton Scattering • Uc = K1pnf(E) gives the Compton coefficient • Ratio of penetration depths between two output fluxes is given by x2 = x1 u2/u1ln(I2/I1) • Penetration depth depends on energy, intensity, and object density Source: Towe and Jacobs 1981

  5. Detecting Backscatter Source: Herr et al 1994

  6. Subtraction of Images Source: Towe and Jacobs 1981

  7. Modern Backscatter Source: Kaufman and Carlson 2010

  8. Fooling the Detector • Monte Carlo simulation using parameters from real detectors • Cylindrical tissue represents the abdomen • Ran simulation four times: • No added material • 160 g of added tissue • 190 g of added TATP explosive • 320 g of added PETN explosive • Formed cone of material 20 cm in diameter and 1 cm high at center Source: Kaufman and Carlson 2010

  9. Source: Kaufman and Carlson 2010

  10. Source: Kaufman and Carlson 2010

  11. Health Concerns • About 1 μSv dose per exposure. • This results in increased cancer risk of 10-7 per round trip • With 1 billion exposures per year, the population risk is no longer minimal • Millimeter wave imaging, which is non-ionizing, may provide a viable imaging alternative for airport security Source: Brenner 2011

  12. Works Cited

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