Segmented MRI Magnet Cooling With a Smaller Cryogen Vessel
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Solution Overview
Problem
Conventional superconducting magnet structures for MRI systems require large cryogen vessels, leading to high costs, material inefficiency, and unreliable helium supply issues, as well as complexity in cooling loop arrangements and gradient coil heat load management.
Innovation Solution
A smaller cryogen vessel design for the inner magnet with separate cooling arrangements for both inner and outer coils, utilizing bonded heat exchangers and reduced cryogen mass, which eliminates the need for a large encompassing cryogen vessel and simplifies the cooling loop, allowing for thinner materials and reduced pressure retaining joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a large encompassing cryogen vessel is used to cool superconducting coils, then sufficient cooling is achieved, but the vessel volume and cryogen mass increase significantly
Solution Approach 1:
The patent divides the cooling system into separate zones: an inner cryogen vessel for the magnet structure and an outer cryogen vessel for the gradient coils. This segmentation allows each vessel to be optimized independently, reducing the total volume required while maintaining effective cooling of all components.
2Temperature
If a large encompassing cryogen vessel is used, then cooling coverage is sufficient, but production costs and material requirements increase
Solution Approach 1:
By segmenting the cryogen vessels, the patent reduces the total volume of pressure-retaining materials required, lowering manufacturing costs. The smaller inner vessel can be produced more economically while still providing adequate cooling for the magnet structure.
Solution Approach 2:
The patent applies different cooling strategies to different regions: the inner vessel provides intensive cooling for the magnet structure, while the outer vessel handles gradient coil cooling. This local differentiation optimizes material usage and reduces overall production costs.
3Ease of manufacture
If cryogen vessel size is reduced, then production costs decrease, but cooling effectiveness may be compromised
Solution Approach 1:
The segmented vessel design ensures that cooling effectiveness is maintained by dedicating the inner vessel specifically to the magnet structure, where it provides intensive cooling without the volume constraints of a larger encompassing vessel.
Solution Approach 2:
The inner cryogen vessel acts as an intermediary cooling system that directly contacts the magnet structure, providing efficient heat removal without requiring the gradient coils to be immersed in cryogen, thus reducing total cryogen volume while maintaining cooling effectiveness.
4Quantity of substance
If a cooling loop arrangement is used to eliminate the encompassing cryogen vessel, then cryogen mass is reduced, but system complexity increases
Solution Approach 1:
The patent extracts the gradient coils from the inner cryogen vessel environment, placing them in the ambient temperature region between the inner and outer vessels. This eliminates the need for complex cooling loops while maintaining reduced cryogen mass.
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 solution reduces the volume and mass of cryogen required, lowers production costs, simplifies the cooling system, and effectively intercepts gradient coil heat loads, making the system more economically viable and efficient.
Implementation Method 1
superconducting coils are typically at least partially immersed in a liquid cryogen at its boiling point
Implementation Method 2
liquid cryogen at its boiling point
Implementation Method 3
One or more thermal radiation shields 16 are provided in the vacuum space between the cryogen vessel 12 and the outer vacuum chamber (OVC) 14
Implementation Method 4
The refrigerator 17 provides active refrigeration to cool cryogen gas within the cryogen vessel 12, in some arrangements by recondensing it into a liquid
Data Source
AI summary
A superconducting magnet structure has a number of axially aligned superconducting inner magnet coils that form an inner magnet structure (30) and a number of superconducting outer coils each having an inner diameter greater than an outer diameter of each of the inner magnet coils. The inner magnet structure is enclosed within a cryogen vessel, and the outer coils are located outside of the cryogen vessel, in thermal contact with a cooling arrangement for cooling the outer coils.