Composite Vacuum Vessel for MRI Eddy Current Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face issues with eddy currents in metal vacuum vessels, leading to unwanted field distortions and increased heat loads, which affect image quality and operational costs, while also requiring a reliable pressure boundary to prevent leaks.
Innovation Solution
A vacuum vessel made of non-metallic composite materials with annular flanges and metal interfaces is used, where the inner and outer cylinders are formed from composite materials like carbon fiber or glass fiber, and metal connectors are welded to minimize eddy currents and ensure a leak-free pressure boundary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal vacuum vessels are used, then structural strength and pressure boundary reliability are improved, but eddy currents are generated causing field distortions and heat loads
Solution Approach 1:
The vacuum vessel uses a composite structure combining non-conductive materials (fiberglass reinforced plastic, foam core) with strategic metal components (flanges, connectors). The non-conductive materials eliminate eddy currents in the vacuum chamber walls while metal flanges and connectors provide structural strength and vacuum sealing capability. This composite approach resolves the contradiction by separating the functions of electrical insulation and structural support.
Solution Approach 2:
The vacuum vessel is divided into multiple segments: non-conductive cylindrical sections for the vacuum chamber, metal flanges for structural connection, and metal connectors for assembly. This segmentation allows each component to be optimized for its specific function - non-conductive materials for eliminating eddy currents and metal components for providing structural strength.
2Strength
If metal vacuum vessels are used, then structural integrity is improved, but heat load increases due to eddy current heating
Solution Approach 1:
The composite construction with non-conductive fiberglass and foam materials eliminates eddy current heating in the vacuum chamber walls while maintaining structural integrity through metal flanges and connectors. This reduces the heat load on the cryogenic system compared to a fully metal construction.
Solution Approach 2:
The conductive metal material is extracted from the vacuum chamber walls and retained only in localized flanges and connectors where structural strength is required. This removal of metal from the main vacuum vessel body eliminates the source of eddy current heating while preserving necessary structural functions.
3Object-generated harmful factors
If non-metallic materials are used for vacuum vessel, then eddy currents are reduced, but manufacturing complexity increases due to welding requirements
Solution Approach 1:
The composite design integrates non-conductive materials for the vacuum chamber with metal flanges and connectors for structural functions. This approach manages manufacturing complexity by using conventional metal fabrication techniques for the metal components while accepting the complexities of composite construction for the non-conductive sections.
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 solution significantly reduces eddy current-induced field distortions and heat loads, maintaining a reliable vacuum environment and improving image quality while ensuring structural integrity and preventing gas permeation.
Implementation Method 1
an inner cylinder formed of a non-metallic material in which eddy currents are substantially reduced during an operation of the at least one gradient coil
Implementation Method 2
attaching metal connectors to a non-flanged end on each of the first and second halves and welding the metal connectors to connect the first and second halves
Data Source
AI summary
A vacuum vessel assembly includes an inner cylinder and an outer cylinder formed of a material in which eddy currents are substantially not produced. The inner cylinder includes a first and second half having an annular flange thereon. A plurality of metal interfaces are connected to the inner cylinder and the outer cylinder. The plurality of metal interfaces bond the first half and second half of the inner cylinder and also bond the inner cylinder to the outer cylinder.