Analysis of a proposed Compton backscatter imaging technique

Conference · Tue Dec 01 04:00:00 EST 1992

OSTI ID:10190087

Hall, J.; Jacoby, B.

Imaging techniques which require access to only one side of the object being viewed are potentially useful in situations where conventional projection radiography and tomography cannot be applied, such as looking for voids in a large container where access to the back of the object is inconvenient or even impossible. One-sided imaging techniques are currently being used in nondestructive evaluation of surfaces and shallow subsurface structures. In this work we present both analytical calculations and detailed Monte Carlo simulations aimed at assessing the capability of a proposed Compton backscatter imaging technique designed to detect and characterize voids located several centimeters below the surface of a solid. The proposed technique, based on a scheme suggested by Farmer and Collins, encodes the spatial position and structure of voids in a solid in the energy spectrum of the Compton-scattered photons as recorded by a high resolution detector. Our calculations model a {sup 137}Cs source projecting a 1 mm{sup 2} pencil beam of 662 keV gammas into a target slab at an incident angle of 45{degrees} and a collimated detector (also oriented at 45{degrees} with respect to the surface) which views the beam path at a central angle of 90{degrees}. The detector collimator is modeled here as a triangular slit viewing a 2.54 cm (1.000``) segment of the beam path at a depth of 2 cm below the surface of the slab. Our results suggest that the proposed technique should be capable of an absolute position resolution of {approx} 0.25 mm ({approx} 0.010``) for isolated voids and an overall object resolution of {approx} 1.00 Ip/mm ({approx} 0.04``). The predicted signal contrast for voids packed with various contraband materials will be discussed as well as multiple scattering contributions to the predicted yields.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10190087
• Report Number(s): UCRL-JC--113254; CONF-9310164--3; ON: DE93040537
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420500
665100
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BACKSCATTERING
COMPTON EFFECT
GAMMA RADIOGRAPHY
IMAGE PROCESSING
MATERIALS TESTING
MEASURING METHODS
MONTE CARLO METHOD
NONDESTRUCTIVE TESTING
NUCLEAR TECHNIQUES IN CONDENSED MATTER PHYSICS
SURFACES
TOMOGRAPHY
X-RAY RADIOGRAPHY