Fiber-Optic Scintillator Gamma Rejection via Interposer Spacing
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Solution Overview
Problem
Fiber-based scintillation neutron detectors with closely packed fibers suffer from poor gamma rejection ratios, leading to interference with neutron signals, and existing methods to improve this either increase system complexity or reduce neutron sensitivity.
Innovation Solution
Spacing out the optical cores of fibers with an interposer material of high density (>1.3 g/cm3) and low average atomic number (<13) to effectively reject gamma rays, with optimal spacing of twice the core diameter between fibers, and using materials like silicon dioxide, graphite, or organic polymers to absorb Compton electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical fibers are closely packed in a bundle for planar coverage, then area coverage is improved, but gamma rejection ratio deteriorates
Solution Approach 1:
The optical fiber bundle is segmented into individual fibers with spacing between them, rather than being closely packed. This segmentation allows gamma rays to be rejected at the fiber level while maintaining overall area coverage through the array configuration of spaced fibers.
Solution Approach 2:
A non-scintillating interposer material is introduced as an intermediary substance filling the spaces between optical fibers. This interposer material absorbs Compton electrons generated by gamma rays, preventing them from traveling between fibers and generating false scintillation signals, thereby improving gamma rejection while maintaining area coverage.
2Measurement precision
If interposer material is used to increase gamma rejection ratio, then gamma rejection ratio is improved, but system complexity increases
Solution Approach 1:
The interposer material is integrated directly into the fiber bundle structure during manufacturing, merging the gamma rejection function with the mechanical support structure. This integration eliminates the need for separate gamma rejection components, reducing system complexity while achieving high gamma rejection ratios.
Solution Approach 2:
The interposer material inherently provides both structural support and gamma rejection functions through its physical properties (density and atomic number). The material serves multiple purposes simultaneously, eliminating the need for additional electronic logic circuitry or complex systems to achieve gamma rejection.
3Measurement precision
If interposer material with high density is used to reject gamma rays, then gamma rejection ratio is improved, but neutron sensitivity may be reduced
Solution Approach 1:
The interposer material is strategically placed only in the regions between fibers where gamma ray interaction would cause problems, while maintaining low atomic number properties in these specific locations. This localized application of high density material with low atomic number achieves gamma rejection without interfering with neutron detection in the fiber cores.
Solution Approach 2:
The interposer material parameters are specifically optimized with high density (>1.3 g/cm³) to stop Compton electrons, combined with low average atomic number (<13) to minimize photoelectron production. This parameter optimization allows the material to reject gamma rays effectively while maintaining neutron sensitivity of the scintillator fibers.
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 achieves a significantly improved gamma rejection ratio of approximately 105:1, reducing gamma interference while maintaining neutron sensitivity without adding complexity, using materials like silicon dioxide, graphite, or organic polymers to absorb Compton electrons and optimize fiber spacing.
Implementation Method 1
a Compton electron (which may be generated from a gamma ray) may cross through multiple fibers in the fiber bundle
Implementation Method 2
the interposer material and the spacing of the optical cores together provide a gamma rejection ratio for the detector of approximately 105:1
Implementation Method 3
Scintillating materials are commonly used in radiation detectors. Such materials typically indicate the presence of a neutron flux by the emission of scintillation photons
Implementation Method 4
where it is gathered for analysis in photomultiplier tubes
Data Source
AI summary
A fiber-optic scintillator radiation detector includes a multitude of optical fibers that each include an optical core. The optical cores are spaced apart from one another by an interposer material. In various embodiments, the interposer material has an average atomic number less than 13 and a density greater than 1.3 g/cm3.