Differential Pressure X-Ray Analysis for Atmospheric Samples
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Solution Overview
Problem
Current x-ray analysis techniques face challenges in analyzing specimens at atmospheric pressure due to vacuum instability, charge accumulation on insulating samples, and inefficient x-ray detection, which limits the analysis of 'wet' or non-conductive materials and reduces spatial resolution.
Innovation Solution
An x-ray analysis apparatus with a focused electron beam assembly and a distributed x-ray detector system positioned in a vacuum environment, utilizing a differential pressure element like an electron-transparent membrane to maintain pressure differential and minimize x-ray absorption, allowing efficient detection of x-rays generated from specimens at higher pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the x-ray detector is positioned in the atmospheric pressure environment close to the sample, then the solid angle for x-ray detection is increased, but x-rays are strongly absorbed by the gaseous atmosphere
Solution Approach 1:
The system divides the detection space into two pressure zones: a vacuum environment for the electron beam and high-energy x-ray detection, and an atmospheric pressure environment for sample placement. This segmentation allows each zone to be optimized for its specific function without compromise.
Solution Approach 2:
A differential pumping aperture acts as an intermediary between the vacuum and atmospheric pressure environments. It allows controlled gas flow while maintaining the pressure differential, enabling the detector to remain in vacuum while the sample is accessed from the atmospheric side.
2Adaptability or versatility
If the specimen is placed in atmospheric pressure environment, then 'wet' samples and insulating materials can be analyzed, but the electron beam scatters on gas molecules reducing spatial resolution
Solution Approach 1:
The electron beam generation and propagation is segregated into a vacuum environment to maintain beam quality and spatial resolution, while only the sample and x-ray detection interact with the atmospheric pressure environment. This allows high-resolution analysis of diverse sample types.
Solution Approach 2:
The differential pumping aperture serves as an intermediary that allows the electron beam to pass from vacuum to atmospheric pressure with minimal scattering, enabling the beam to maintain its focussed state while interacting with samples in atmospheric conditions.
3Reliability
If a small aperture is used to isolate vacuum for electron beam, then vacuum is maintained, but the aperture severely limits the range of deflection for the electron beam
Solution Approach 1:
The system dynamically manages pressure zones, maintaining vacuum only where the electron beam is generated and detected, while allowing atmospheric pressure where the sample is placed. This dynamic pressure management enables both beam control and sample accessibility.
Solution Approach 2:
The problem is solved by adding the pressure dimension as a differentiating factor between zones. Rather than using a single pressure environment, the system uses differential pressure zones to simultaneously achieve beam quality and sample accessibility.
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
Enables high spatial resolution x-ray elemental analysis of specimens at partial or full atmospheric pressure by minimizing x-ray absorption and ensuring clear line of sight for detection, thereby improving analysis efficiency for both conductive and non-conductive samples.
Implementation Method 1
x-ray spectrum is measured by sensing and measuring the energies of individual x-ray photons emitted by a specimen when it is hit by a focussed electron beam
Implementation Method 2
An evacuated electron column generates, accelerates, and focuses electrons and is isolated from the ambient atmosphere by a thin, electron transparent membrane
Implementation Method 3
Each x-ray photon is an energetic particle and the energy is typically converted into charge using a solid state detector
Implementation Method 4
low energy x-rays are strongly absorbed by air at atmospheric pressure
Data Source
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Figure 5
AI summary
An x-ray analysis apparatus comprises an electron beam assembly for generating a focused electron beam within a first gas pressure environment. A sample assembly is used for retaining a sample within a second gas pressure environment such that the sample receives the electron beam from the electron beam assembly and such that the gas pressure in the second gas pressure environment is greater than the gas pressure within the first gas pressure environment. An x-ray detector is positioned so as to have at least one x-ray sensor element within the first gas pressure environment. The sensor element is mounted to a part of the electron beam assembly which is proximal to the sample assembly and further arranged in use to receive x-rays generated by the interaction between the electron beam and the sample.