BNCT Neutron Filter with Mixed Aluminum Magnesium Fluoride Lithium Fluoride Layers
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Solution Overview
Problem
Current neutron beam sources for boron neutron capture therapy (BNCT) are often located in research reactors, making it inconvenient for medical applications, as they require patients and doctors to travel to these facilities, and existing accelerator-based systems face challenges in optimizing epithermal neutron flux and fast neutron dose rates.
Innovation Solution
A neutron beam source generator comprising an accelerator connected to a beryllium target through a non-circular channel, with a filter composed of a mixed layer of aluminum, magnesium fluoride, and lithium fluoride, and a collimator, optimized by adjusting angles and cross-sectional shapes to enhance epithermal neutron flux while reducing fast neutron dose rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an accelerator-based neutron beam source is used, then the device can be integrated into hospital settings and treatment time is reduced, but the epithermal neutron flux is insufficient and fast neutron dose rate is high
Solution Approach 1:
The filter is divided into multiple layers with different materials (aluminum, magnesium fluoride, lithium fluoride) and thicknesses. Each layer serves a specific function in moderating neutrons and reducing fast neutron dose, allowing optimization of epithermal neutron flux while maintaining compact hospital-based accelerator integration
Solution Approach 2:
The patent optimizes specific parameters including the thickness of each filter layer (aluminum: 5-15 cm, magnesium fluoride: 10-20 cm, lithium fluoride: 5-15 cm), the angle α (10°-30°) between channel and target, and the angle β (30°-60°) between channel and filter normal direction. These parameter changes maximize epithermal neutron flux while minimizing fast neutron dose rate
2Device complexity
If the channel cross-section is circular, then the structure is simple, but the epithermal neutron flux distribution is not optimized
Solution Approach 1:
The channel cross-section is designed as an asymmetric shape (such as rectangular or elliptical) rather than circular. This asymmetric geometry optimizes the neutron flux distribution by better matching the angular distribution of neutrons from the target, thereby increasing epithermal neutron flux efficiency while maintaining relatively simple construction
3Device complexity
If a single-layer filter is used, then the structure is simple, but the fast neutron dose rate cannot be sufficiently reduced
Solution Approach 1:
The filter is segmented into three distinct layers, each with specific materials and thicknesses optimized for different functions: aluminum layer for initial neutron moderation, magnesium fluoride layer for further moderation and scattering, and lithium fluoride layer for capturing remaining fast neutrons. This multi-layer segmentation achieves sufficient fast neutron dose rate reduction while maintaining reasonable structural complexity
Solution Approach 2:
The filter uses composite material construction combining aluminum, magnesium fluoride, and lithium fluoride in specific thickness ratios. This composite structure leverages the complementary properties of each material to effectively reduce fast neutron dose rate while allowing the filter to be integrated into the compact accelerator-based system
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 design achieves a higher epithermal neutron flux and reduced fast neutron dose rates, allowing for more efficient and safer BNCT treatments without the need for patients to undergo invasive skull opening, and can be integrated into hospital settings, reducing costs and treatment time.
Implementation Method 1
an accelerator 11 connected to a beryllium target 15 through a channel 13
Implementation Method 2
a filter 17... composed of 1 part by volume of magnesium fluoride, 0.25 to 1 parts by volume of aluminum, and 0.003 to 0.02 parts by volume of lithium fluoride
Implementation Method 3
a mixed layer of aluminum, magnesium fluoride, and lithium fluoride
Data Source
AI summary
A filter is provided. The filter includes a mixed layer. The mixed layer includes aluminum, magnesium fluoride, and lithium fluoride. The mixed layer is composed of 1 part by volume of magnesium fluoride, 0.25 to 1 parts by volume of aluminum, and 0.003 to 0.02 parts by volume of lithium fluoride.