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

Abstract

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 collimatormore » 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.« less

Inventors:

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

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+ Show Inventor Affiliations

1. Helotes, TX
2. Ann Arbor, MI

Issue Date:

2003-01-01

Research Org.:

Oak Ridge Associated Univ., Oak Ridge, TN (United States)

OSTI Identifier:

875090

Patent Number(s):

6528797

Application Number:

09/549994

Assignee:

The Regents of the University of Michigan (Ann Arbor, MI)

Patent Classifications (CPCs):

G - PHYSICS G01 - MEASURING G01V - GEOPHYSICS

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G - PHYSICS G01 - MEASURING G01V - GEOPHYSICS

G01V5/02 - specially adapted for surface logging, e.g. from aircraft

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DOE Contract Number:  

AC05-76OR00033

Resource Type:

Patent

Country of Publication:

United States

Language:

English

Subject:

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; /250/