Ionizing Radiation Detector Calibration via Position-Dependent Correction

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Solution Overview

Problem

Ionizing radiation detectors, particularly those using semiconductor materials like CdTe or CdZnTe, face challenges in spatial homogeneity due to varying signal responses based on the location of interactions within the detector, leading to non-uniform detection responses.

Innovation Solution

A calibration method is developed to determine correction factors based on the position of interactions within the detector, using a correction function associated with a position parameter to weight signal amplitudes, allowing for automated calibration and accounting for 3D positions of interactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If semiconductor detector materials (CdTe, CdZnTe) are used with polarized electrodes for charge carrier collection, then the detector can generate electronic signals for energy estimation, but the signal collected by an electrode depends on the location of the interaction in the detector material, resulting in non-spatially homogeneous response

Engineering Contradiction:
Improveenergy measurement precisionVSAvoidspatial response uniformity
Core Design Contradiction:
Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by introducing position-dependent correction factors that modify the detected signal based on the interaction location. The correction factor varies as a function of position parameters (depth, radial distance, or 3D coordinates), transforming the non-uniform response into a corrected uniform response. This allows the detector to maintain its inherent position-dependent signal variation while compensating for it through mathematical correction, thereby achieving spatially homogeneous measurement precision without altering the physical detector structure.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If electrodes are segmented into elementary electrodes for imaging applications, then spatial resolution is improved, but the signal produced by an interaction depends on the position of the interaction with respect to the elementary electrodes, increasing the complexity of calibration

Engineering Contradiction:
Improvespatial resolutionVSAvoidcalibration complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent simplifies calibration by changing the parameter space from multiple independent electrode responses to a unified position-dependent correction model. Instead of calibrating each elementary electrode separately, the invention uses a single correction factor function that depends on position parameters (depth, radial distance, or 3D coordinates). This reduces the calibration complexity from O(N) where N is the number of elementary electrodes to O(1) by parameterizing the correction in terms of spatial coordinates, thereby maintaining high spatial resolution while significantly reducing calibration complexity.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If correction factors are determined for different depths and radial distances using charge sharing, then spatial homogeneity is improved, but the calibration process requires multiple measurement channels and iterative procedures, increasing the time and resources needed

Engineering Contradiction:
Improvespatial response uniformityVSAvoidcalibration time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent reduces calibration time by changing from a multi-step iterative calibration process to a single-step parameter-based correction. Instead of performing separate calibrations for different depths and radial distances and then combining them, the invention directly applies a correction factor that is a function of position parameters. This can be implemented with a single measurement channel by determining the interaction position and applying the corresponding correction factor, thereby achieving the same spatial homogeneity improvement while significantly reducing calibration time and resource requirements.

Inventive Principle:
Principle #35Parameter changes

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 method enhances the spatial homogeneity of detector responses by applying position-dependent correction factors, improving the accuracy of ionizing radiation detection by accounting for the location of interactions, thereby correcting for the non-uniformity in signal generation.

Implementation Method 1

Each interaction, whether photoelectric interaction or Compton scattering, or even pair creation, generates several hundred or even thousands of electron-hole pairs

Methodology Applied
Scientific EffectPhotoelectric interaction: Photoelectric Effect

Implementation Method 2

Each interaction, whether photoelectric interaction or Compton scattering, or even pair creation, generates several hundred or even thousands of electron-hole pairs

Methodology Applied
Scientific EffectCompton scattering: Compton Scattering

Implementation Method 3

Electrons migrate to the anode(s), while holes migrate to the cathode(s). Thus, an interaction is an event generating charge carriers in the semiconductor material, these charges migrating towards the electrodes polarizing the detector

Methodology Applied
Scientific EffectElectron migration: Electron Beam

Implementation Method 4

These electrodes allow the polarization of the detector material. They also allow the collection of charge carriers generated by the interactions of ionizing radiation in the detector material

Methodology Applied
Scientific EffectElectric field: Electric Field

Data Source

PatentEP3237931B8Method for calibrating an ionising radiation detector and associated device
Publication Date: 2019.01.23 IDEMIA IDENTITY & SECURITY FRANCE SAS

AI summary

The invention relates to a method for calibrating an ionising radiation detector, with the aim of determining a correction factor in order to establish an amplitude-energy correspondence. The invention first relates to a method for calibrating a device for detecting ionising radiation, the detector comprising a semiconductor or scintillator detection material capable of generating a signal S of amplitude A upon interaction between ionising radiation et said detection material, the method including the determination of a weighting factor at the amplitude A.