Superconducting Magnet Helium Thermal Buffer
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Solution Overview
Problem
Cryogen-free superconducting magnets have limited thermal buffering capacity at cryogenic temperatures, which can lead to issues during power outages, cooling liquid outages, or cryocooler failures, requiring ramping down and subsequent ramping up of the static magnetic field.
Innovation Solution
Incorporating gas-tight containers filled with helium in thermally conductive contact with the superconducting coil windings and members, providing additional thermal capacity to maintain the magnetic field stability during such events by utilizing the high specific heat capacity of helium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If cryogen-free cooling technology is used to eliminate helium consumption, then helium consumption is reduced, but thermal buffering capacity is limited
Solution Approach 1:
The thermal buffering system is segmented into multiple independent gas-tight containers (202, 204, 206) distributed throughout the magnet structure, each containing helium at different pressures. This segmentation allows the system to maintain reliability through distributed thermal capacity while keeping each container manageable in size and pressure.
Solution Approach 2:
Helium gas serves as an intermediary thermal buffer between the superconducting coils and the external environment. The helium containers act as thermal mediators that absorb and release heat to maintain coil temperature stability during disturbances, eliminating the need for direct cryogenic liquid contact.
2Reliability
If thermal buffering capacity is increased to improve reliability during outages, then ride-through time is extended, but system complexity increases
Solution Approach 1:
The helium-filled gas-tight containers serve multiple functions simultaneously: they provide thermal buffering capacity, act as pressure vessels for stored energy, and serve as structural components integrated into the magnet assembly. This multi-functionality extends ride-through time without proportionally increasing system complexity.
Solution Approach 2:
The system uses parameter changes in helium pressure (ranging from 10 bar to 500 bar) to optimize thermal capacity within fixed-volume containers. By varying pressure rather than volume, the design achieves extended ride-through times while maintaining manageable container sizes and overall system complexity.
3Reliability
If gas-tight containers with high pressure helium are used to increase thermal capacity, then thermal buffering is improved, but safety risks increase
Solution Approach 1:
The total thermal buffering capacity is divided into multiple segmented containers rather than one large high-pressure vessel. This segmentation distributes the pressure risk across multiple smaller units, reducing the consequences of potential failures while maintaining total thermal capacity.
Solution Approach 2:
The system incorporates safety margins and pressure relief mechanisms in advance to cushion against potential overpressure scenarios. The containers are designed with predetermined pressure limits and safety features that activate before dangerous pressure levels are reached, protecting the system from harmful effects.
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 enhances the thermal buffering capacity, allowing for extended ride-through times and reduced cooling capacity requirements, enabling safer and more reliable operation of cryogen-free superconducting magnets by omitting the need for ramping down the static magnetic field during events like power outages or cryocooler failures.
Implementation Method 1
the at least one gas-tight container is in thermally conductive contact to the at least one coil winding for taking up thermal energy from the at least one coil winding
Implementation Method 2
At cryogenic temperatures, for instance below 10 K, the specific heat capacity (i.e. the heat capacity per unit mass) of helium gas exceeds the specific heat capacities of most metals by many orders of magnitude
Data Source
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AI summary
A superconducting magnet device (14; 46), including at least one coil winding (161-164) of superconducting wire, configured for generating a static magnetic field B0, wherein the at least one coil winding (161-164) is adapted to establish a thermally conductive contact with a cold head (38) of a cryocooler that is configured for bringing to and keeping the at least one coil winding (161-164) at a temperature below the critical temperature, and at least one gas-tight container (40;48) that permanently contains an amount of helium, wherein the at least one gas-tight container (40; 48) is in thermally conductive contact to the at least one coil winding (161-164) for taking up thermal energy from the at least one coil winding (161-164) in at least one operational state; and a magnetic resonance imaging system (10) that is configured for acquiring magnetic resonance images from at least a portion of a subject of interest (22), comprising such a superconducting magnet device (14; 46) for generating a static magnetic field B0 in an examination space (20) of the magnetic resonance imaging system (10).