Method and system for determining depth distribution of radiation-emitting material located in a source medium and radiation detector system for use therein

Patent · Wed Jan 01 00:00:00 EST 2003

OSTI ID:875090

Benke, Roland R ^[1]; Kearfott, Kimberlee J ^[2]; McGregor, Douglas S ^[2]

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1. Helotes, TX
2. Ann Arbor, MI

A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take samples, such as extensive soil samples, to determine the depth distribution. The system includes a portable detector assembly with an x-ray or gamma-ray detector having a detector axis for detecting the emitted radiation. The radiation may be naturally-emitted by the material, such as gamma-ray-emitting radionuclides, or emitted when the material is struck by other radiation. The assembly also includes a hollow collimator in which the detector is positioned. The collimator causes the emitted radiation to bend toward the detector as rays parallel to the detector axis of the detector. The collimator may be a hollow cylinder positioned so that its central axis is perpendicular to the upper surface of the large area source when positioned thereon. The collimator allows the detector to angularly sample the emitted radiation over many ranges of polar angles. This is done by forming the collimator as a single adjustable collimator or a set of collimator pieces having various possible configurations when connected together. In any one configuration, the collimator allows the detector to detect only the radiation emitted from a selected range of polar angles measured from the detector axis. Adjustment of the collimator or the detector therein enables the detector to detect radiation emitted from a different range of polar angles. The system further includes a signal processor for processing the signals from the detector wherein signals obtained from different ranges of polar angles are processed together to obtain a reconstruction of the radiation-emitting material as a function of depth, assuming, but not limited to, a spatially-uniform depth distribution of the material within each layer. The detector system includes detectors having different properties (sensitivity, energy resolution) which are combined so that excellent spectral information may be obtained along with good determinations of the radiation field as a function of position.

• Research Organization: Oak Ridge Associated Universities (ORAU), Oak Ridge, TN (United States)
• DOE Contract Number: AC05-76OR00033
• Assignee: The Regents of the University of Michigan (Ann Arbor, MI)
• Patent Number(s): US 6528797
• Application Number: 09/549994
• OSTI ID: 875090
• Country of Publication: United States
• Language: English

Related Subjects

method
determining
depth
distribution
radiation-emitting
material
located
source
medium
radiation
detector
provided
distributed
contaminated
field
samples
extensive
soil
determine
portable
assembly
x-ray
gamma-ray
axis
detecting
emitted
naturally-emitted
gamma-ray-emitting
radionuclides
struck
hollow
collimator
positioned
causes
bend
rays
parallel
cylinder
central
perpendicular
upper
surface
allows
angularly
sample
ranges
polar
angles
forming
single
adjustable
set
pieces
configurations
connected
configuration
detect
selected
range
measured
adjustment
enables
signal
processor
processing
signals
obtained
processed
obtain
reconstruction
function
assuming
limited
spatially-uniform
layer
detectors
properties
sensitivity
energy
resolution
combined
excellent
spectral
information
determinations
position
radiation detector
upper surface
radiation field
emitting material
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