Segmented Photon Counting Detector Electrode Design
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Solution Overview
Problem
Direct conversion photon counting detectors face limitations in reducing pulse width due to charge sharing and polarization effects, which affect the detectable photon flux rate and energy resolution, especially in configurations like steering electrodes and coplanar grids.
Innovation Solution
The detector employs a highly segmented electrode pixel configuration with a collecting electrode, a non-collecting electrode, and a steering electrode, where the steering electrode is operated at a lower potential to guide electrons towards the collecting electrode, reducing polarization effects and allowing for shorter pulse widths without the need for large potential differences between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electrode pixel area is reduced to narrow detectable pulse width, then detectable photon flux rate increases, but cross-talk between adjacent electrode pixels due to charge sharing worsens
Solution Approach 1:
The electrode pixel is divided into multiple collecting electrodes (first and second collecting electrodes) with intermediate electrodes positioned between them. This segmentation allows each collecting electrode to have a smaller effective area for charge collection, reducing cross-talk to adjacent pixels while maintaining a larger overall pixel area for higher photon flux detection capability.
Solution Approach 2:
Different regions within the electrode pixel are assigned different functions: the first and second collecting electrodes are optimized for charge collection, the intermediate electrodes are optimized for reducing cross-talk by creating localized field regions, and the third electrode provides additional field control. This local differentiation resolves the contradiction between pixel area and cross-talk.
2Duration of action of moving object
If collecting electrode area is reduced to obtain narrower pulses, then detectable pulse width narrows, but the area dedicated to electron or hole collecting decreases
Solution Approach 1:
The collecting function is distributed across multiple collecting electrodes (first and second) rather than concentrated in a single large electrode. Each collecting electrode can be smaller in area while collectively providing sufficient collection capability, enabling narrower pulse widths without sacrificing total collection area.
Solution Approach 2:
Intermediate electrodes are positioned between the first and second collecting electrodes to mediate the electric field distribution. These intermediate electrodes help confine the electric field lines to specific regions, allowing the collecting electrodes to be smaller while maintaining effective charge collection and achieving narrower pulse widths.
3Duration of action of moving object
If steering electrode configuration is used to reduce pulse width, then detectable pulse width is reduced, but charges are trapped near the collecting electrode which polarizes the detector and distorts the electrical field
Solution Approach 1:
The electrode structure is segmented into multiple collecting electrodes with intermediate electrodes positioned between them. This segmentation distributes the charge collection function across multiple smaller electrodes, reducing charge accumulation at any single location and thereby minimizing polarization effects and electrical field distortion while maintaining narrow pulse widths.
Solution Approach 2:
Intermediate electrodes act as mediators that control and distribute the electric field between the first and second collecting electrodes. By providing additional field control points, these intermediate electrodes prevent field distortion and polarization that would otherwise occur with simpler steering electrode configurations, ensuring reliable operation.
4Reliability
If coplanar grid configuration is used, then charges are distributed over larger areas reducing polarization, but a relatively large potential difference is required between closely neighboring collecting and non-collecting electrodes
Solution Approach 1:
The electrode pixel is segmented into multiple collecting electrodes (first and second) with intermediate electrodes positioned between them. This segmentation allows charges to be distributed over multiple smaller collection points, achieving polarization reduction similar to coplanar grids but with lower potential difference requirements due to the optimized geometric arrangement and field control.
Solution Approach 2:
Different electrode regions are optimized for different functions: collecting electrodes for charge collection, intermediate electrodes for field control and polarization reduction. This local differentiation allows the system to achieve both low potential difference operation and effective polarization reduction by placing each electrode type in its optimal position and configuration.
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 reduces pulse duration, supports higher count rates, and minimizes polarization effects, enabling more efficient detection of photons with reduced noise and manufacturing complexity compared to prior art designs.
Implementation Method 1
the steering electrode is operated at a lower potential to guide electrons towards the collecting electrode
Implementation Method 2
inbound radiation (such as x-rays, γ-rays) is absorbed by the direct conversion material and, due to a photoelectric interaction, mobile electron-hole pairs are generated in the direct conversion material
Data Source
Figure 1~2
Figure 3a~4b
Figure 5a~5e
AI summary
The present invention discloses a pixilated direct conversion photon counting detector with a direct conversion material layer and a pixilated electrode. Individual electrode pixels are segmented into three segments (510, 520, 530), wherein one of the segments (520) is operated at a more electrically repellant value than that of the other two (510, 530). Said other two segments are connected to electric circuitry (610, 611, 620, 630) that is arranged to generate signals which are indicative of a count of electrons or holes that approach each of the respective electrode pixel segments and to subtract the generated signals from each other.