CdZnTe Pixel Detector Depth Sensing via Polarity Ratio
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Solution Overview
Problem
CdZnTe detectors face challenges in accurately measuring interaction depth of signals, which affects spectral response, image resolution, and differentiating between source and background events.
Innovation Solution
A method involving a CdZnTe pixel detector connected to an ASIC that measures both positive and negative polarity signal amplitudes, allowing calculation of interaction depth by determining the ratio of positive signal amplitudes from surrounding 'hallow' pixels to the negative signal amplitude of the 'core' pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only single polarity signal amplitude is measured, then device complexity is reduced, but measurement precision of interaction depth is lost
Solution Approach 1:
The detector is divided into multiple pixels with segmented readout capabilities, where each pixel can measure both positive and negative polarity signals. This segmentation allows the system to extract depth information from the spatial distribution of signals across multiple pixels while maintaining the ability to measure both charge polarities for accurate depth calculation.
Solution Approach 2:
The ASIC serves as an intermediary between the detector pixels and the processing system, providing the capability to measure both positive and negative polarity signal amplitudes. This intermediary device enables depth measurement by calculating the ratio of positive to negative signal amplitudes across core and hallow pixels, resolving the contradiction between measurement precision and device complexity.
2Reliability
If depth sensing capability is added, then spectral response and image resolution are improved, but device complexity increases
Solution Approach 1:
The pixel detector system is designed to perform multiple functions: it can measure event energy, determine lateral position, and sense interaction depth simultaneously. By making the detector multi-functional, the system achieves improved spectral response and image resolution without requiring separate dedicated systems for each measurement type, thus managing the increase in device complexity.
Solution Approach 2:
The system utilizes changes in signal amplitude parameters (positive and negative polarity ratios) to extract depth information. By analyzing the ratio of positive to negative signal amplitudes across different pixels, the system transforms the complex three-dimensional interaction depth measurement into a manageable parameter ratio calculation, improving reliability while controlling complexity.
3Measurement precision
If both positive and negative polarity signals are measured, then interaction depth can be calculated, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces complex mechanical or physical depth measurement mechanisms with an electrical signal ratio-based calculation system. By substituting the need for direct physical depth measurement with an electrical measurement approach (comparing positive to negative signal amplitudes), the system achieves depth calculation accuracy while reducing the stringency of manufacturing precision requirements for the detector structure itself.
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 approach enhances spectral response, improves image resolution, and effectively differentiates between source and background events, particularly in Compton and coded aperture applications.
Implementation Method 1
upon interactions of photons in the CdZnTe pixel detector
Implementation Method 2
applying a bias on the CdZnTe pixel detector such that a segmented contact of the CdZnTe pixel detector collects electrons
Data Source
AI summary
Interaction depth of photons in a CdZnTe pixel detector is measured by configuring an ASIC connected to the detector to measure both positive polarity and negative polarity signal amplitudes and then measuring a core pixel having positive signal amplitude and hallow pixels having negative signal amplitude and surrounding the core pixel.