Moving Radiation Source Detection via Frequency Domain Convolution
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Solution Overview
Problem
Current methods for detecting moving radioactive sources in nuclear security applications face challenges in differentiating threat sources from ambient background noise, especially when independent background measurements are not possible, and summation of detector responses only increases sensitivity as the square root of the number of detectors, limiting the effectiveness of detection.
Innovation Solution
A system and method that analyze detector responses in the frequency domain to separate dynamic and static components, using the convolution of multiple detector responses to extract the velocity and presence of a moving radiation source without requiring separate background measurements, enhancing sensitivity and field of view by correlating responses across multiple detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If collimation is used to reduce background noise, then background noise is reduced, but the solid angle from which detectors can observe radiation is reduced and the observation time for moving sources is reduced
Solution Approach 1:
The patent extracts the dynamic component (moving source signal) from the total detector response by analyzing the frequency domain characteristics. The Fourier transform separates the time-varying signal from the static background, allowing removal of background without physical shielding or collimation.
Solution Approach 2:
The patent replaces the mechanical approach of collimation (physical shielding) with a signal processing approach using Fourier transform analysis. Instead of physically blocking background radiation, the system uses frequency domain filtering to distinguish and extract the moving source signal from background noise.
2Measurement precision
If separate background measurements are made, then threat source presence can be differentiated by background subtraction, but the variance of background measurement increases with background intensity and independent measurements are not always practical
Solution Approach 1:
The system uses the detectors themselves to simultaneously measure both the moving source signal and the background radiation. The Fourier transform analysis of the detector responses allows self-extraction of the dynamic component without requiring separate background measurement instruments or procedures.
Solution Approach 2:
The patent enables continuous measurement of both source and background signals simultaneously through Fourier transform analysis of ongoing detector responses. This eliminates the need to stop or pause measurements for separate background characterization, maintaining continuous monitoring capability.
3Measurement precision
If summation of multiple detector responses is used, then detection sensitivity is improved, but the improvement only increases as the square root of the number of detectors
Solution Approach 1:
The patent changes the parameter combination method from simple summation to convolution in the frequency domain. By transforming detector responses to the frequency domain, applying convolution operations, then transforming back, the system achieves enhanced sensitivity that scales more favorably with the number of detectors than simple summation.
Solution Approach 2:
The patent moves the analysis from the time domain to the frequency domain using Fourier transforms. This dimensional transformation allows convolution operations that exploit the correlated time profiles of multiple detectors, achieving better sensitivity scaling by utilizing the temporal dimension of the signals.
4Adaptability or versatility
If independent background measurements are not possible, then background subtraction cannot be performed, but the invention provides an alternative method to differentiate moving sources without separate background measurements
Solution Approach 1:
The patent introduces the Fourier transform as an intermediary mathematical tool that processes the raw detector responses. This transform acts as a mediator that reveals the dynamic component embedded within the total signal, enabling source differentiation without direct background measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables rapid and accurate identification of moving radiation sources, improving sensitivity and eliminating the need for collimators, thereby enhancing the detection of moving sources beyond the limitations of existing methods.
Implementation Method 1
a means for detecting incoming radiation (such means being virtual detectors created from a single detector, or a plurality of actual detectors)
Implementation Method 2
determining the Fourier transform of the counting rate function for each detector and extracting from the Fourier transform the velocity of the source and the ambient radiation background
Implementation Method 3
determining the convolution of the counting rate functions for combinations of (e.g. pairs of) detectors at different locations and extracting therefrom information concerning the presence, intensity, and position of the source
Data Source
AI summary
The invention provides a method for detecting a moving radiation source, the method comprising placing a plurality of radiation detectors at one or more locations; collecting information of counting rate as a function of time for each detector, computing the Fourier transform of the counting rate function for each detector and extracting from the computed Fourier transform the dynamic component of the detector response for each detector, and computing the convolution of the counting rate functions for combinations of detectors at different locations, then extracting therefrom information concerning the presence of radiation sources moving with respect to the radiation detectors.