Ferromagnetic Shielding in Superconducting Magnet Apparatus
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Solution Overview
Problem
Existing superconductor magnet apparatuses face challenges in achieving high homogeneity and stability of magnetic fields due to external ferromagnetic shielding, which can be inaccurate and temperature-sensitive, and require cumbersome mechanical force control.
Innovation Solution
The ferromagnetic shielding body is placed within the cryostat during the field-cooling charging procedure, ensuring accurate alignment and temperature stabilization, with a design that extends beyond the superconductor bulk magnet and has a larger cross-sectional area to effectively shield stray fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ferromagnetic shielding is placed outside the cryostat, then stray field shielding is achieved, but alignment accuracy deteriorates and temperature stability is compromised
Solution Approach 1:
The ferromagnetic shielding body is nested inside the cryostat, placing the shielding structure within the existing cryogenic environment. This eliminates the need for external shielding assembly while ensuring precise alignment with the superconductor bulk magnet and maintaining temperature stability through the cryostat's controlled environment.
Solution Approach 2:
The ferromagnetic shielding body is pre-positioned within the cryostat before the superconductor bulk magnet is installed. This preliminary arrangement ensures that the shielding is already in place and properly aligned when the magnet is inserted, eliminating post-charging shielding operations and associated mechanical force control issues.
2Object-affected harmful factors
If ferromagnetic shielding is added after charging, then stray field protection is provided, but mechanical force control becomes cumbersome
Solution Approach 1:
The ferromagnetic shielding body is pre-positioned within the cryostat before the superconductor bulk magnet is installed and charged. This eliminates the need to handle and position heavy ferromagnetic shielding components after charging, when strong magnetic forces would be present, thereby avoiding cumbersome mechanical force control requirements.
Solution Approach 2:
The shielding system is segmented into the ferromagnetic shielding body integrated with the cryostat structure, separating the shielding function from the superconductor bulk magnet. This integration allows the shielding to be installed independently before charging, avoiding the need to control mechanical forces during post-charging shielding installation.
3Object-affected harmful factors
If ferromagnetic shielding body is large enough to effectively shield stray fields, then shielding performance improves, but device complexity increases
Solution Approach 1:
The ferromagnetic shielding body is merged with the cryostat structure, combining two functional elements into a single integrated design. This eliminates the need for separate external shielding components, reducing overall device complexity while maintaining effective stray field shielding performance through the adequately sized ferromagnetic body.
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 approach achieves better homogeneity and stability of the trapped magnetic field, eliminating the need for post-charging shielding and reducing mechanical forces, while maintaining a compact and thermally stable design suitable for applications like NMR experiments.
Implementation Method 1
a ferromagnetic shielding body with a shielding bore, wherein the superconductor bulk magnet is arranged within the shielding bore of the ferromagnetic shielding body
Implementation Method 2
superconducting electric currents are induced within the superconductor bulk magnet, opposing the change of magnetic flux, and as a result trapping (or conserving) the magnetic field
Implementation Method 3
The superconducting state of a superconductor is only assumed below a critical temperature Tcrit, which is in the cryogenic range
Data Source
AI summary
A superconductor magnet apparatus (2) includes a superconductor bulk magnet (9), a cryostat (7) and a ferromagnetic shielding body (11). The bulk magnet has a superconductor bore (10), an axis (z) of rotational symmetry, and a maximum outer diameter ODbm in a plane perpendicular to the z axis. The superconductor bore has a minimum cross-sectional area Sbo in a plane perpendicular to the z axis. The cryostat has a room temperature bore (8), the bulk magnet is arranged within the cryostat and the room temperature bore is arranged within the superconductor bore. The shielding body has a shielding bore (12), the bulk magnet is arranged within the shielding bore and the shielding body extends beyond the bulk magnet at each axial end by at least ODbm/3. For an average cross-sectional area Sfb of the shielding body, Sfb≥2.5*Sbo, and the shielding body is arranged within the cryostat.