Scintillator Rod Light Concentration for Harsh Environment Radiometry
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Solution Overview
Problem
Radiometric process measurement systems face challenges in achieving a favorable signal-to-noise ratio and economic production, especially in harsh environments, due to the limitations of photomultipliers and the inefficiency of scintillation light detection in extended detectors.
Innovation Solution
The use of an optical light concentration device to focus scintillation light from a larger scintillator rod cross-sectional area onto a smaller active area of a sensor unit, potentially using a parabolic light-collecting lens or gradient lens, to enhance detection efficiency and reduce costs by minimizing the number of photosensors required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photomultipliers based on tube technology are used, then high sensitivity and large active area are achieved, but they are only suitable to a limited extent for use in harsh environments
Solution Approach 1:
The patent changes the material parameter of the photosensor from vacuum tube photomultiplier to semiconductor photodiode, which has different physical and chemical properties. Semiconductor materials are more robust against harsh environmental conditions (temperature, vibration, shock) while maintaining photosensitive functionality, thus resolving the contradiction between reliability in harsh environments and sensitivity.
2Reliability
If photodiodes or silicon photomultipliers are used, then they are more suitable for harsh environments, but they can currently only be produced economically with a relatively small active area
Solution Approach 1:
The patent segments the scintillator rod into multiple sections along its length, with each section having a different refractive index. This segmentation allows the use of multiple small-area semiconductor photosensors to effectively cover a larger detection area, as each photosensor detects light from its corresponding scintillator section, thus resolving the contradiction between small active area and sufficient detection coverage.
Solution Approach 2:
The patent introduces an optical light concentration device as an intermediary between the scintillator rod and the photosensor. This device collects and concentrates scintillation light from the scintillator rod onto the smaller active area of the semiconductor photosensor, enabling efficient light detection despite the limited photosensor area, thus resolving the contradiction between small active area and detection effectiveness.
3Measurement precision
If the entire scintillator surface is made photosensitive, then the signal-to-noise ratio is improved, but costs increase and mechanical construction becomes complicated
Solution Approach 1:
The patent applies local quality by making only specific portions of the scintillator rod photosensitive - specifically, sections with different refractive indices that correspond to the positions of the photosensors. This selective photosensitivity optimization improves the signal-to-noise ratio by directing light efficiently to photosensors while avoiding the complexity of making the entire surface photosensitive.
4Area of stationary object
If reflected light is used to reach the photosensor, then the light path is extended, but the probability of light absorption in the scintillator increases before hitting the photosensor
Solution Approach 1:
The patent replaces the mechanical/optical system of light reflection with a refractive index gradient system. By creating sections with different refractive indices along the scintillator rod, light is naturally directed toward the photosensors through refraction rather than reflection, shortening the light path and reducing absorption losses while still achieving comprehensive area coverage.
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 improves the signal-to-noise ratio and reduces energy consumption and noise, allowing for highly sensitive process measurement systems that can be used in harsh environments with fewer and smaller semiconductor-based photodiodes, while maintaining cost-effectiveness.
Implementation Method 1
a rod detector serving as a scintillation detector, which has a rod-shaped scintillator element which can extend at least over part of the height of the container or the length of a tube. The rod-shaped scintillator element is also referred to as a scintillator rod in this application.
Implementation Method 2
directs a proportion of the scintillation light, which is produced when ionizing radiation is irradiated along the active length of the scintillator rod, in the manner of a light guide inside the scintillator rod directly and/or by optionally multiple total reflections on the lateral surface of the scintillator bar toward an end face
Implementation Method 3
A sensor unit with at least one photosensor for converting scintillation light emerging from the end face into electrical signals is assigned to the scintillator rod.
Data Source
Figure 1
Figure 2~3
Figure 4~5B
AI summary
A process measurement system (100) for the radiometric measurement of at least one process parameter by means of ionizing radiation comprises a scintillator rod (200) having an end face (210) designed as an exit surface for scintillation light from the scintillator rod, and a sensor unit (220) with at least one photosensor for converting scintillation light exiting the end face and striking an active surface (222) of the sensor unit into electrical signals. The active surface (222) of the sensor unit (220) is smaller than the mean light-guiding cross-sectional area of the scintillator rod (200). An optical light concentration device (250) is provided for concentrating scintillation light towards the active surface of the sensor unit.