Neutron Detector Phosphor Light Transmission Layer Discrimination
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Solution Overview
Problem
Current neutron detectors face challenges in distinguishing neutrons from gamma rays in high dose conditions due to low neutron-absorbing efficiency and long decay times of phosphor materials, leading to reduced detection efficiency and temporal resolution.
Innovation Solution
A neutron detector with a layered structure comprising thin-film phosphor and light transmission layers, where the phosphor layer contains a neutron-absorbing isotope like 6Li or 10B, and the light transmission layer is made of silicon dioxide, with a refractive index ratio between 0.90 to 1.10, allowing for high n/γ discrimination and efficient neutron detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phosphor with large luminescence amount is used to increase n/γ discrimination ability, then discrimination ability is improved, but decay time becomes long and fast response is reduced
Solution Approach 1:
The scintillator is divided into multiple phosphor layers separated by light transmission layers. Each phosphor layer contains neutron-absorbing isotopes (6Li or 10B) and emits scintillation light when neutrons are absorbed. The light transmission layers allow efficient light extraction while maintaining the segmented structure that reduces gamma ray interaction paths, achieving both fast response and high discrimination ability.
Solution Approach 2:
The detector uses a composite structure combining phosphor materials with neutron-absorbing isotopes (6Li or 10B) and light transmission materials (silicon dioxide or other transparent materials). This composite approach allows optimization of both neutron absorption cross-section and light transmission properties, resolving the contradiction between discrimination ability and response speed.
2Productivity
If the phosphor layer thickness is increased to improve neutron detection efficiency, then detection efficiency is improved, but sensitivity to gamma rays increases
Solution Approach 1:
The phosphor is segmented into multiple thin layers separated by light transmission layers. This segmentation allows neutrons to traverse multiple layers increasing absorption probability (improving detection efficiency), while the light transmission layers in between reduce the continuous path length for gamma rays, decreasing gamma ray sensitivity.
Solution Approach 2:
The detector transitions from a single thick phosphor layer to a multi-layered structure where light transmission layers are inserted between phosphor layers. This dimensional change in the scintillator structure allows simultaneous optimization of neutron detection efficiency (through multiple interaction opportunities) and gamma ray rejection (through reduced interaction paths).
3Measurement precision
If 3He gas is used to increase n/γ discrimination ability, then discrimination ability is improved, but resolution time becomes long and detection becomes difficult in high dose conditions
Solution Approach 1:
The patent replaces the gas-based proportional counter (3He gas) with a solid-state scintillator system using phosphor materials containing neutron-absorbing isotopes (6Li or 10B). This substitution eliminates the long resolution time issue inherent in gas proportional counters while maintaining high n/γ discrimination ability through the phosphor's neutron absorption characteristics and scintillation light emission.
4Productivity
If a thick gas layer is made to measure epithermal and fast neutrons with high efficiency, then detection efficiency is improved, but apparatus size and cost increase
Solution Approach 1:
The patent changes the fundamental parameter of the detector medium from gas (3He) to solid phosphor material containing neutron-absorbing isotopes. This parameter change enables high detection efficiency for both epithermal and fast neutrons without requiring a thick gas layer, thereby reducing apparatus size and cost while maintaining or improving discrimination ability.
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 detector achieves high efficiency in measuring high neutron doses with improved n/γ discrimination ability and temporal resolution, reducing sensitivity to gamma rays while maintaining neutron detection efficiency.
Implementation Method 1
a phosphor that emits fluorescent light by absorbing the energy of charged particles, wherein the phosphor contains a neutron-absorbing isotope that emits secondary charged particles by absorbing the neutrons
Implementation Method 2
detects neutrons by fluorescent light emitted when the neutrons are absorbed by a phosphor
Implementation Method 3
a thin-film form light transmission layer made of a light transmitting material that transmits the fluorescent light and is adjacent to the phosphor layer in the thickness direction
Implementation Method 4
a photodetector configured to issue an output pulse as output generated on detecting the fluorescent light
Data Source
AI summary
To obtain a neutron detector capable of measuring high dose neutrons with high neutron/gamma-ray discrimination ability and high efficiency.A scintillator 10 has a layered structure in which a phosphor layer 11 and a light transmission layer 12 are alternately laminated in z direction. The phosphor layer 11 is made of a phosphor material emitting fluorescent light by absorbing neutrons, the material being, for example, a scintillator material used in neutron detectors having already been known. The light transmission layer 12 is made of a material highly transmitting fluorescent light emitted by the phosphor material and only slightly absorbing neutrons. In the scintillator 10, when neutrons and gamma-ray photons enter it, luminescence intensity (pulse height) due to neutrons is significantly different from that due to gamma-ray photons. It makes it easy to discriminate between outputs due to the two kinds of radiations.