Compact X-ray Source with Low Bragg Angle Monochromator
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Solution Overview
Problem
Conventional X-ray sources for X-ray photoelectron spectroscopy (XPS) are bulky and protrude from the vacuum chamber due to their tall aspect ratio, limiting space and increasing costs, while also having a poor solid angle of X-ray capture and low X-ray flux due to the use of quartz-based monochromators.
Innovation Solution
A compact, linear X-ray source configuration with a tubular housing that fits within the vacuum chamber, featuring an electron gun, target, and a monochromator, where the target, monochromator, and focal point are positioned within the housing diameter, using materials like mica crystals to reduce the Bragg angle and increase X-ray flux, and incorporating cooling systems for heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quartz-based monochromator is used, then the X-ray source can be configured with a standard geometry, but the solid angle of X-ray capture is poor and X-ray flux is low
Solution Approach 1:
The patent changes the Bragg angle parameter from the conventional high angle (quartz-based) to a low angle (less than 45 degrees) by using alternative crystal materials such as mica, sapphire, or diamond. This parameter change enables a compact linear geometry while maintaining monochromator function and increasing X-ray flux by a factor of 10 or more.
Solution Approach 2:
The patent employs composite crystal structures, combining different crystal materials (mica, sapphire, diamond) with specific geometric configurations to achieve both low Bragg angle operation and high X-ray flux. The composite approach allows optimization of both monochromator performance and productivity.
2Volume of moving object
If the X-ray source is made compact to fit within the vacuum chamber, then space is saved and costs are reduced, but the solid angle of X-ray capture may be limited
Solution Approach 1:
The patent transitions from a tall, vertical configuration to a compact linear arrangement that fits within the vacuum chamber diameter. By repositioning components along the linear axis and using low Bragg angle geometry, the system achieves compactness without sacrificing capture efficiency.
Solution Approach 2:
Changing the Bragg angle to a low value enables the monochromator crystal to be positioned closer to the target while still effectively capturing and monochromatizing X-rays, thus achieving compactness while maintaining capture efficiency.
3Manufacturing precision
If electrons are focused onto a small spot on the target, then spatial resolution is improved, but heat dissipation becomes difficult and target damage may occur
Solution Approach 1:
The patent introduces a low Bragg angle monochromator configuration that acts as an intermediary, allowing the electron beam to be focused on a small spot for high spatial resolution while the monochromator geometry distributes and manages the thermal load more effectively.
Solution Approach 2:
The low Bragg angle configuration changes the geometric parameters of the X-ray generation system, which indirectly affects heat distribution and dissipation dynamics, allowing better thermal management at the focused spot.
4Measurement precision
If a monochromator is used to select a narrow wavelength band, then energy resolution and signal-to-noise ratio are improved, but X-ray flux is reduced due to wavelength suppression
Solution Approach 1:
The patent changes the Bragg angle parameter to a low value, which fundamentally alters the monochromator's angular acceptance and efficiency characteristics. This parameter change allows the monochromator to maintain narrow wavelength selection while transmitting significantly higher X-ray flux compared to conventional high-angle configurations.
Solution Approach 2:
The use of advanced crystal materials (diamond, sapphire, mica) with optimized low-angle geometry creates a composite system that achieves both high energy resolution and high flux transmission, overcoming the traditional trade-off between monochromatization efficiency and flux preservation.
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 configuration allows for a more compact, cost-effective X-ray source with improved X-ray flux and spatial resolution, reducing analysis time and enhancing the signal-to-noise ratio, while maintaining the ability to focus X-rays onto a small spot on the sample.
Implementation Method 1
An electron gun produces electrons with sufficient velocity to produce the required X-rays from the target material
Implementation Method 2
X-rays are produced when the electrons strike the target
Implementation Method 3
Electrons ejected from the atoms of the target material are replaced by electrons further from the nucleus—it is this that produces X-rays at a number of discrete wavelengths, or 'lines'
Implementation Method 4
The monochromator crystal makes use of a phenomenon known as Bragg diffraction to selectively focus X-rays onto the sample
Implementation Method 5
The copper of the anode assembly may be water cooled, and the region of the target that bears the electron impact may be coated directly onto diamond, which conducts heat several times better than copper
Data Source
AI summary
An X-ray source comprising:an elongate tubular housing adapted to be fitted into a port of and extend into a chamber containing a sample to be analyzed, said housing containing: an electron gun and a target mounted in the housing, the electron gun being arranged to direct electrons to a point on the target such that the target radiates X-rays; anda monochromator arranged to focus X-rays radiated from the target to a focal point on a sample in the chamber;wherein the monochromator is positioned, and comprises a material selected such that the target, the monochromator and the focal point on the sample are substantially in-line within the envelope of the tubular housing.