X-Ray Chopper Wheel Geometry for Higher-Energy Scanning
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Solution Overview
Problem
Existing x-ray backscatter imaging systems face challenges in achieving higher x-ray energies due to the rapid increase in chopper disk thickness and weight, which limits system complexity and cost. Additionally, bulky backscatter detectors cannot be easily mounted externally on vehicles for mobile imaging systems, requiring extensive modifications to the vehicle enclosure.
Innovation Solution
The system employs a rotating chopper wheel with radial slits oriented at an acute angle relative to the x-ray fan beam, allowing for higher x-ray energies while reducing the thickness and weight of the chopper disk. Additionally, wavelength-shifting fiber (WSF) detectors with a thin profile are mounted externally on vehicles, eliminating the need for extensive modifications to the vehicle enclosure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the end-point x-ray energy is increased to improve detection capability, then the x-ray penetration ability is improved, but the chopper disk thickness and weight increase rapidly
Solution Approach 1:
The patent changes the orientation of the chopper disk from a conventional perpendicular arrangement to a tilted arrangement where the disk plane forms an acute angle with the x-ray beam direction. This dimensional reorientation allows the x-ray beam to pass through the disk at a glancing angle, effectively increasing the path length through the attenuating material without increasing the physical thickness of the disk, thereby reducing weight while maintaining high-energy x-ray attenuation capability
Solution Approach 2:
The patent modifies the geometric parameters of the chopper disk system by introducing a tilt angle parameter. By optimizing this angle, the system achieves effective attenuation of high-energy x-rays with a thinner, lighter disk. The parameter change transforms the relationship between disk thickness and effective attenuation path length
2Reliability
If the chopper disk thickness is increased to attenuate higher energy x-rays, then the x-ray attenuation capability is improved, but the system weight and moment of inertia increase
Solution Approach 1:
The patent employs a tilted chopper disk configuration where the disk is oriented at an acute angle relative to the incident x-ray beam. This geometric transformation allows the beam to traverse a longer effective path through the attenuating material without requiring increased disk thickness, thereby maintaining attenuation reliability while reducing weight
3Reliability
If bulky backscatter detectors are used to improve detection performance, then the detection capability is improved, but the ease of external mounting on vehicles deteriorates
Solution Approach 1:
The patent adopts thin-film wavelength-shifting fiber (WSF) detector technology that replaces traditional bulky detector assemblies. These thin-profile detectors can be directly mounted on the exterior vehicle surfaces without requiring extensive structural modifications, thereby maintaining detection capability while dramatically improving ease of installation and system integration
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 x-ray scanning systems to operate at significantly higher x-ray energies with reduced weight and cost, while also allowing for external mounting of backscatter detectors on vehicles, simplifying system integration and reducing costs.
Implementation Method 1
The apertures used to create the pencil beams for BX imaging are typically formed through materials that attenuate the initial x-ray beam by at least a factor of 10^8
Implementation Method 2
an x-ray source configured to produce a collimated fan beam of incident x-ray radiation
Implementation Method 3
measuring the intensity of the backscattered x-rays as a function of the position of the pencil beam on the target
Data Source
AI summary
An x-ray scanning system, and corresponding method, includes an x-ray source that produces incident x-ray radiation having end-point x-ray energy, which, in various embodiments, can be greater than about 200 keV, between about 200 keV and about 500 keV, or greater than about 500 keV. The system also includes a disk chopper wheel that can be irradiated by and attenuate the incident x-ray radiation. The disk chopper wheel further defines one or more slits configured to pass the incident x-ray radiation through the disk chopper wheel for scanning a target. In some embodiments, the high end-point x-ray energies with disk chopper wheels are facilitated by forming the incident x-ray radiation as a collimated fan beam and/or orienting the chopper wheel with a wheel plane substantially non-perpendicular to a fan beam plane, increasing effective thickness of a disk chopper wheel to attenuate incident x-rays of higher energies.