Topics Source of x-rays Interaction with matter Detection and Processing Fooling the Detector Health...
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Transcript of Topics Source of x-rays Interaction with matter Detection and Processing Fooling the Detector Health...
X-ray Backscatter Detectors
By Mark Guseman
TopicsSource 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•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
Compton ScatteringUc = 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
Detecting Backscatter
Source: Herr et al 1994
Subtraction of Images
Source: Towe and Jacobs 1981
Modern Backscatter
Source: Kaufman and Carlson 2010
Fooling the DetectorMonte 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
Source: Kaufman and Carlson 2010
Source: Kaufman and Carlson 2010
Health ConcernsAbout 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
Works Cited