Gadolinium-Doped Plastic Scintillator for Thermal Neutron Detection
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Solution Overview
Problem
Current thermal neutron detection technologies face challenges in efficiently discriminating neutron signals from gamma and X-ray signals, particularly due to low capture cross-sections of boron-10 and lithium-6, and require expensive inorganic scintillators for effective detection, leading to limitations in sensitivity and cost.
Innovation Solution
A thermal neutron detection device comprising two concentric plastic scintillator blocks, one doped with gadolinium, which enhances detection through differential gamma-ray event counting and utilizes a photon reflector and fluorescence photon conversion systems to isolate and quantify thermal neutrons, overcoming limitations of previous technologies by balancing light yields and improving signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plastic scintillators doped with boron-10 or lithium-6 are used for thermal neutron detection, then the device can discriminate neutron signals from gamma signals using pulse shape analysis, but the capture cross-sections are too low to compete with helium-3 technology
Solution Approach 1:
The detector is divided into two separate scintillator blocks: a first block doped with gadolinium-157 for thermal neutron detection and a second block for gamma-ray detection. This segmentation allows independent optimization of each detector's properties and enables differential measurement to isolate neutron signals from gamma background.
Solution Approach 2:
The invention changes the dopant material from boron-10 or lithium-6 to gadolinium-157, which has a much higher thermal neutron capture cross-section (600,000 barns compared to 3,840 barns for boron-10). This parameter change dramatically improves detection sensitivity while maintaining plastic scintillator advantages.
2Measurement precision
If inorganic crystalline scintillators are used to observe the photoelectric peak for gamma-ray detection, then gamma-ray discrimination is improved, but the cost increases significantly
Solution Approach 1:
The invention replaces expensive inorganic crystalline scintillators with inexpensive plastic scintillators. While plastic scintillators have lower intrinsic gamma-ray discrimination, the system achieves effective gamma-ray detection through differential measurement between two plastic blocks, one doped with gadolinium-157.
3Device complexity
If a single scintillator block is used for both thermal neutron and gamma-ray detection, then the device structure is simplified, but the ability to discriminate neutron signals from gamma background is reduced
Solution Approach 1:
The detector is divided into two separate scintillator blocks: a first block doped with gadolinium-157 for thermal neutron detection and a second block for gamma-ray detection. This segmentation allows independent optimization of each detector's properties and enables differential measurement to isolate neutron signals from gamma background.
Solution Approach 2:
The invention uses the differential response of two scintillator blocks as an intermediary measurement approach. By comparing signals from the gadolinium-doped block (sensitive to both neutrons and gamma) and the undoped block (sensitive primarily to gamma), the system indirectly isolates the neutron signal through mathematical subtraction, achieving effective discrimination without requiring complex pulse shape analysis.
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
The device effectively detects and quantifies thermal neutrons by leveraging gadolinium's high radiative capture cross-section, providing improved sensitivity and cost-effectiveness compared to existing methods, while reducing the need for expensive inorganic scintillators and minimizing parasitic scintillation signals.
Implementation Method 1
Gadolinium presents a cross section for the radiative capture of thermal neutrons which has a high value
Implementation Method 2
a first scintillator block (1) doped with gadolinium... which collects the fluorescence photons emitted by the first scintillator block
Implementation Method 3
a photon reflector (3) which separates the first scintillator block (1) from the second scintillator block (2) so as to isolate a channel by which the first scintillator block (1) emits fluorescence photons
Implementation Method 4
a fluorescence photon conversion system (4-5,17) which collects the fluorescence photons emitted by the first and second scintillator blocks and outputs an electrical signal
Data Source
Figure 1
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Figure 3~4
AI summary
The invention relates to a device for detecting thermal neutrons comprising a first scintillator block (1) and a second scintillator block (2), the second scintillator block (2) being placed inside an inner space of the first scintillator block (1), said device being characterised in that: the first (1) and second (2) scintillator blocks are plastic scintillator blocks with substantially identical volumes, each containing at least one fluorophore, the first or second scintillator block being doped with gadolinium; a photon reflector (3) separates the first scintillator block (1) from the second scintillator block (2) such as to isolate a path via which the first scintillator block (1) emits fluorescence photons from a path by which the second scintillator block (2) emits fluorescence photons; a system for converting fluorescence photons (4, 5) collects the fluorescence photons emitted by the first and second scintillator blocks and outputs a signal representing gamma photons detected by the first and second scintillator blocks; and a processing system (9) outputs a signal which translates the presence or absence of thermal neutrons from the signal representing gamma photons detected by the first and second scintillator blocks.