Adaptive Multi-Energy X-ray Cargo Inspection
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Solution Overview
Problem
Current cargo inspection systems using dual-energy X-ray methods are less effective for high-energy inspections due to weak Z-dependence of Compton scatter, leading to ambiguity in determining atomic numbers and requiring multiple beams or tandem-detector configurations that are inefficient and prone to cross-contamination, especially at energies above 1 MeV.
Innovation Solution
A method employing a temporal sequence of X-ray pulses with evolving spectral content, where each pulse is characterized by an onset and varying spectral content over time, allowing for material characterization by processing detector signals across distinct time intervals tailored to the pulse's spectral content, using a linac to generate pulses up to 10 MeV and employing detectors like scintillation or Cherenkov detectors to differentiate signal responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual-energy X-ray methods are used for cargo inspection, then material discrimination capability is improved, but at high energies above 1 MeV the Z-dependence of Compton scatter becomes weak causing ambiguity in determining atomic numbers
Solution Approach 1:
The pulse sequence is segmented into multiple time intervals, each corresponding to different effective energies. By processing detector signals from distinct time intervals separately, the system obtains multiple energy measurements from a single pulse, enabling material discrimination without requiring multiple simultaneous beams.
Solution Approach 2:
The system utilizes the dynamic evolution of spectral content within each X-ray pulse over time. The effective energy of the pulse changes during its duration, allowing the system to capture transmission data at multiple energy levels by integrating detector signals over different time intervals within the same pulse.
2Measurement precision
If multiple beams or tandem-detector configurations are used to overcome Compton scatter limitations, then material discrimination is improved, but device complexity and susceptibility to cross-contamination increase
Solution Approach 1:
The system combines multiple energy measurements into a single pulse sequence, merging the functionality of what would traditionally require multiple beams or tandem detectors. By processing signals from different time intervals of one pulse, the system achieves multi-energy material discrimination with a single beam path and detector configuration.
Solution Approach 2:
A single detector serves multiple functions by measuring transmission at different effective energies during different time intervals of the pulse sequence. The same physical detector configuration performs what would traditionally require multiple specialized detectors or beam lines.
3Length of stationary object
If high-energy X-rays up to 10 MeV are used for penetration, then penetration capability through thick cargo is improved, but the weak Z-dependence of Compton scatter at these energies reduces measurement precision
Solution Approach 1:
The system employs periodic pulsing of the X-ray source with each pulse containing temporal variations in spectral content. By using a sequence of such pulses with different time interval integrations, the system periodically samples transmission at different effective energies, enabling precision measurement even at high penetration energies where Compton scatter dominates.
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 enhances material discrimination by accurately determining effective atomic numbers and electron densities, reducing ambiguity and improving dynamic range, especially in scenarios with varying cargo densities, and allows for efficient high-speed scanning without the need for multiple beams or tandem detectors.
Implementation Method 1
generating a temporal sequence of pulses of penetrating radiation, each pulse characterized by an onset and by a spectral content that evolves with time subsequent to the onset
Implementation Method 2
In the range of 1-10 MeV, however, X-ray interaction is dominated by the Compton effect with its weak dependence of attenuation coefficient (mass absorption) on the atomic number
Implementation Method 3
In the practice of dual-energy inspection, X-ray transmission data of an inspected object are obtained for both energies, and processed by computer
Implementation Method 4
employing detectors like scintillation or Cherenkov detectors to differentiate signal responses
Implementation Method 5
employing detectors like scintillation or Cherenkov detectors to differentiate signal responses
Data Source
AI summary
Methods and systems for x-ray inspection of an object using pulses whose spectral composition varies during the course of each pulse. A temporal sequence of pulses of penetrating radiation is generated such that the spectral content of each pulse evolves with time. The pulses are formed into a beam that is scanned across the object and detected after traversing the object. The detector signal is processed to derive at least one material characteristic of the object, such as effective atomic number, on the basis of temporal evolution of the detector signal during the course each pulse of the sequence of pulses. The time intervals may be predetermined, or else adapted based on features of the detected signal.