Cryostat Magnetic Shielding With Internal Superconducting Coils
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Solution Overview
Problem
Existing cryostat active shielding arrangements are sub-optimal due to distortion by passive shielding material, require high currents, and are costly and time-consuming to manufacture, while also lacking precise control over magnetic field gradients.
Innovation Solution
The active magnetic shielding coils are placed inside the cryostat using superconducting Niobium-Titanium wire, which allows for reduced current requirements, optimized shielding performance, and precise control over magnetic fields, with passive shielding located outside the coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active shielding coils are placed outside the cryostat, then heat generation from coils is avoided, but shielding performance is degraded due to distortion by passive shielding material and requires high currents
Solution Approach 1:
The patent inverts the conventional arrangement by placing the active shielding coils inside the cryostat rather than outside. This allows the coils to operate in the cryogenic environment where superconducting materials can function with zero electrical resistance, eliminating the need for high currents while providing optimal shielding performance directly at the region of interest.
Solution Approach 2:
The patent changes the temperature parameter of the coil environment from ambient to cryogenic temperatures. This parameter change enables the use of superconducting materials that exhibit zero electrical resistance below a critical temperature, allowing high-current shielding coils to operate without power loss or heat generation.
2Object-affected harmful factors
If passive shielding material is used to create a shielded volume, then magnetic field redirection is achieved, but gaps required for cabling and access degrade shielding performance
Solution Approach 1:
The patent extracts the active shielding function from the passive shielding structure and implements it independently via coils inside the cryostat. This allows the passive shielding to maintain its integrity without gaps, while the active coils provide additional shielding capability that is not compromised by access requirements.
Solution Approach 2:
The patent employs a composite shielding approach combining passive high-permeability materials for flux shunting with active superconducting coils for field cancellation. This composite system achieves superior shielding performance that compensates for any gaps in the passive structure while maintaining access capability.
3Reliability
If high-current coils are used for active shielding outside passive shielding, then field cancellation is achieved, but power costs increase and safety concerns arise
Solution Approach 1:
The patent changes the operating temperature parameter to cryogenic levels, enabling superconducting operation. This parameter change reduces the electrical resistance to zero, allowing the shielding coils to generate strong magnetic fields for effective cancellation without consuming electrical power or generating heat.
Solution Approach 2:
The superconducting coils utilize the cryogenic environment of the cryostat itself to maintain their superconducting state. The cryostat's cooling system serves the dual purpose of cooling the sample and maintaining the coils in their zero-resistance state, eliminating the need for separate power consumption for coil operation.
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 configuration reduces the magnetic noise floor by a factor of 2, improves the response of superconducting circuits, and enhances the overall quality of the shielded environment, while also reducing power requirements and safety concerns.
Implementation Method 1
at least one coil winding within the cryogenically-cooled internal volume for generating a magnetic field in the internal volume to cancel the effect of an ambient magnetic field
Implementation Method 2
passive shields, which utilise high magnetic permeability metal alloys to draw the field into the alloy, redirecting the magnetic field lines around the shielded volume
Data Source
AI summary
A cryostat contains an internal volume for containing an object to be tested at or an apparatus to be operated at a cryogenic temperature, means for reducing the temperature of the internal volume to a cryogenic temperature, and at least one coil winding within the internal volume for generating a magnetic field in the internal volume to cancel the effect of an ambient magnetic field, and passive magnetic shielding located within the internal volume but outside the at least one coil winding.