PeXSA Photo Emitter X-Ray Source Array for Coherent Imaging
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Solution Overview
Problem
Current X-ray sources face difficulties in creating coherent, time-resolved measurements due to the challenges of fabricating gratings for high-energy X-rays and rapidly switching high voltages, which limits their ability for differential phase contrast and other advanced imaging modalities.
Innovation Solution
A Photo Emitter X-Ray Source Array (PeXSA) is developed, utilizing a photocathode electron source illuminated by a laser light source to generate X-rays, which eliminates the need for gratings and enables rapid modulation and patterning of the X-ray source, allowing for coherent, time-resolved measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gratings are used in front of conventional X-ray sources for differential phase contrast, then interferometric measurements can be achieved, but the gratings are very difficult to fabricate for energies higher than 50 KeV and absorb a considerable amount of X-ray radiation
Solution Approach 1:
The patent removes the grating component from the system entirely by using a patterned photocathode source that directly generates the required interference pattern. This extraction eliminates the manufacturing difficulties and X-ray absorption issues associated with gratings while preserving the differential phase contrast measurement capability.
Solution Approach 2:
The patent introduces a patterned photocathode as an intermediary between the laser source and the sample. This photocathode converts optical patterns into electron beam patterns, which then generate X-rays with the desired spatial coherence, serving as a mediator that enables interferometric measurements without requiring physical gratings.
2Measurement precision
If gratings are used in front of conventional X-ray sources, then interferometric measurements can be achieved, but a considerable amount of X-ray radiation is absorbed, reducing the achievable SNR
Solution Approach 1:
The grating component that causes X-ray absorption is completely removed from the system. The patterned photocathode source generates X-rays with the necessary spatial structure directly at the source, eliminating the need for downstream gratings that would absorb X-ray radiation and reduce signal-to-noise ratio.
3Loss of time
If high voltages are switched rapidly on the order of picoseconds with current X-ray sources, then time resolved measurements can be made, but this is very difficult to achieve
Solution Approach 1:
The patent replaces the mechanical/electrical high voltage switching system with an optical control system. A pulsed laser illuminates the photocathode to generate electron bursts, which are then accelerated by a continuously on high voltage. The timing is controlled by the laser pulse duration and timing rather than by switching the high voltage, achieving picosecond time resolution through optical rather than electrical means.
4Ease of manufacture
If a patterned source is used to eliminate gratings, then interferometric measurements can be enabled, but the source must be coherent and rapidly modulatable
Solution Approach 1:
The patterned photocathode serves as an intermediary that converts optical patterns into electron beam patterns with high spatial coherence. The laser light provides the initial coherence, which is transferred to the electron beam through photoemission, and then to the X-ray source, enabling interferometric measurements without gratings.
Solution Approach 2:
The system uses periodic pulsed laser illumination of the photocathode to generate periodically modulated electron beams and corresponding X-ray pulses. This periodic action enables time-resolved measurements and achieves the required modulation capability while maintaining source coherence through the photoemission process.
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 PeXSA achieves high spatial resolution below 20 nm, enables differential phase contrast imaging, and allows for time and spatial dependent measurements, overcoming the limitations of conventional X-ray sources by creating a patterned, coherent X-ray source that can be modulated at high rates.
Implementation Method 1
a photocathode electron source, a laser light source, where the laser light source illuminates the photocathode electron source to emit electrons
Implementation Method 2
an X-ray target, where the emitted electrons are focused on the X-ray target, where the X-ray target emits X-rays
Data Source
AI summary
A photo-emitter x-ray source is provided that includes a photocathode electron source, a laser light source, where the laser light source illuminates the photocathode electron source to emit electrons, and an X-ray target, where the emitted electrons are focused on the X-ray target, where the X-ray target emits X-rays. The photocathode electron source can include alkali halides (such as CsBr and CsI), semiconductors (such as GaAs, InP), and theses materials modified with rare Earth element (such as Eu) doping, electron beam bombardment, and X-ray irradiation, and has a form factor that includes planar, patterned, or optically patterned. The X-ray target includes a material such as tungsten, copper, rhodium or molybdenum. The laser light source is pulsed or configured by light modulators including acousto-optics, mode-locking, micro-mirror array, and liquid crystals, the photocathode electron source includes a nano-aperture or nano-particle arrays, where the nano-aperture is a C-aperture or a circular aperture.