X-ray Window Foil Composite Structure for Low Absorption
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Solution Overview
Problem
Existing radiation window foils face challenges in achieving low X-ray absorption while maintaining mechanical strength, especially when the window is large and exposed to varying temperatures and pressure differences.
Innovation Solution
A radiation window foil structure is developed using a layered configuration with a thin silicon nitride etch stop layer and a monocrystalline silicon first etchable layer, which is bonded and then thinned to create a mesh or grid pattern, enhancing mechanical strength and thermal tolerance by integrating layers without additional glues or attaching means, and optionally reinforced with additional mesh layers for increased durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thin foil is used to reduce X-ray absorption, then X-ray transmission is improved, but mechanical strength deteriorates
Solution Approach 1:
The radiation window foil is constructed as a composite structure with multiple layers: a first foil layer (5-20 µm) providing mechanical strength, a second foil layer (1-5 µm) optimizing X-ray transmission, and an intermediate layer bonding them together. This composite configuration allows the thinner overall structure to transmit X-rays more effectively while the combined layers maintain sufficient mechanical strength.
Solution Approach 2:
The single foil structure is segmented into multiple functional layers with different thicknesses and material properties. The first foil layer is thicker for strength, the second is thinner for X-ray transmission, and they are separated by an intermediate layer. This segmentation allows each layer to optimize its specific function while working together as a whole.
2Area of stationary object
If the window size is increased to cover larger openings, then coverage area is improved, but tolerance to pressure differences deteriorates
Solution Approach 1:
The multi-layer composite structure provides enhanced rigidity and strength-to-weight ratio, allowing larger window areas to withstand pressure differences without excessive deformation. The combination of thicker and thinner layers creates a structurally optimized configuration that maintains integrity across larger surfaces.
3Strength
If additional layers are added to reinforce the foil, then mechanical strength is improved, but X-ray absorption increases
Solution Approach 1:
Different layers have different thicknesses optimized for their specific functions: the first foil layer is thicker (5-20 µm) where mechanical strength is critical, while the second foil layer is thinner (1-5 µm) where X-ray transmission is prioritized. The intermediate layer is positioned locally to bond the foils without adding excessive absorption throughout the entire structure.
Solution Approach 2:
The composite structure strategically combines layers of different thicknesses and materials, allowing the overall structure to achieve both strength and low absorption. The intermediate layer material is specifically selected to provide bonding while minimizing X-ray absorption compared to conventional single-layer designs.
4Strength
If conventional bonding methods (glues, solders, welds) are used to attach the foil to the frame, then attachment strength is improved, but the foil structure is compromised
Solution Approach 1:
The bonding layer is integrated as an inherent part of the multi-layer foil structure rather than being applied as a separate attachment method. This merging of the bonding function into the foil's construction eliminates the need for external glues, solders, or welds, maintaining structure integrity while providing sufficient attachment capability.
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 achieves exceptional tolerance to temperature variations and maintains structural integrity under pressure differences, with coefficients of thermal expansion of the materials closely matched, ensuring minimal X-ray absorption and mechanical robustness.
Implementation Method 1
the first etchable layer 103 and the second etchable layer 101 are bonded together through the van der Waals force
Implementation Method 2
forming a etch stop layer 102 on the top surface of the carrier 101... portions of the first etchable layer 103 are etched away to produce a first mesh or grid layer 107 on the first (top) side of the etch stop layer 102
Implementation Method 3
coefficients of thermal expansion of the materials closely matched, ensuring minimal X-ray absorption and mechanical robustness
Data Source
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AI summary
A radiation window foil is provided for an X-ray radiation window. It comprises a continuous window layer with a first side and a second side. A first mesh or grid layer is stacked on or bonded to said first side of said continuous window layer. A second mesh or grid layer is stacked on or bonded to said second side of said continuous window layer.