High-Z Conversion Layer X-ray Detectors
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Solution Overview
Problem
High-cost scintillator materials like cadmium tungstate and BGO limit the economic viability of multi-row X-ray detectors for cargo scanning, restricting detector performance and scanning speed due to high material costs and the need for thick scintillator layers to absorb high-energy X-rays.
Innovation Solution
A multi-row X-ray image acquisition apparatus using a high-Z conversion layer, such as tungsten, configured edgewise to incident X-ray photons, in conjunction with semiconductor layers to generate electron-hole pairs, allowing for efficient absorption and conversion of X-rays, reducing the need for thick scintillator materials and lowering costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick scintillator materials (30 mm) are used to absorb high-energy X-rays, then X-ray absorption efficiency improves, but detector cost increases significantly
Solution Approach 1:
The patent combines a high-Z conversion layer (tungsten or tantalum) with a semiconductor layer to create a composite detector structure. This composite approach replaces the traditional single-material scintillator, achieving high X-ray absorption efficiency through the high-Z material while avoiding the high cost of thick scintillator blocks. The conversion layer generates electrons that are then detected by the semiconductor, providing both efficiency and cost-effectiveness.
Solution Approach 2:
The patent changes the material parameter from low-Z scintillator materials (cadmium tungstate, BGO) to high-Z materials (tungsten, tantalum). This parameter change enables effective absorption of high-energy X-rays with much thinner material thickness, thereby reducing the quantity of expensive scintillator material required while maintaining or improving absorption efficiency.
2Productivity
If multi-row detectors are implemented to increase scanning speed, then productivity improves, but system cost becomes economically viable only with expensive scintillator materials
Solution Approach 1:
By using high-Z conversion layers combined with semiconductor detectors, the patent enables multi-row detector configurations to be economically viable. The high-Z material provides efficient X-ray absorption without requiring the expensive thick scintillator blocks that would make multi-row systems prohibitively costly, thus allowing increased scanning speed through multiple detector rows.
3Reliability
If conventional scintillator materials (cadmium tungstate, BGO) are used, then X-ray absorption is effective, but material cost is extremely high
Solution Approach 1:
The patent changes the atomic number parameter of the detection material from the conventional low-Z scintillator materials to high-Z materials such as tungsten (Z=74) or tantalum (Z=77). This parameter change enables effective absorption of high-energy X-rays through photoelectric absorption and Compton scattering, achieving comparable or superior absorption effectiveness at a fraction of the material cost.
Solution Approach 2:
The patent replaces expensive scintillator materials with cheaper high-Z materials that can be used in thinner configurations. While the high-Z materials themselves are not inexpensive, the overall detector cost is reduced due to the eliminated need for thick scintillator blocks, making the detection system more economically viable.
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
The solution significantly reduces material costs and enhances detector performance by achieving higher detective quantum efficiency (DQE) with a more efficient absorption of X-rays, making multi-row detectors economically feasible and enabling faster scanning speeds.
Implementation Method 1
Atoms within the scintillator interact with incident X-ray photons and are raised in energy. When the energetically excited atoms in the scintillator decay back to their ground state they emit light.
Implementation Method 2
The incident X-ray photons therefore traverse a 30 mm thickness of the scintillator. This is sufficient to absorb approximately 40% of the incident high energy X-rays
Implementation Method 3
a first semiconducting layer adjacent to the conversion layer for generating electron-hole pairs in response to electrons generated by the conversion layer
Data Source
AI summary
An image acquisition apparatus includes a conversion layer for generating electrons in response to electromagnetic radiation photons, and a first semiconducting layer adjacent to the conversion layer for generating electron-hole pairs in response to electrons generated by the conversion layer.