Dual-Cryogen MRI Cooling System for Quench Prevention
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Solution Overview
Problem
Magnetic resonance imaging (MRI) machines face challenges in maintaining ultra-low temperatures for superconducting magnets, leading to cryogen boil-off and extended downtime during cooling interruptions, such as power outages or cryocooler replacement, which can result in peak temperatures exceeding critical limits.
Innovation Solution
A dual-cryogen cooling system with a primary cooling loop for the superconducting magnet and a secondary thermal battery loop using solid nitrogen to absorb heat, extending the ride-through period and preventing quenching by providing auxiliary cooling through a closed circulation system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cryocooler is used to cool the superconducting magnet, then the cooling system is simple, but the ride-through period is limited and downtime increases when cooling is interrupted
Solution Approach 1:
The cooling system is divided into two independent loops: a primary cooling loop with a first cryocooler for normal operation, and a secondary cooling loop with a second cryocooler as backup. This segmentation allows one cryocooler to fail or require maintenance while the other maintains cooling, thereby extending the ride-through period without significantly increasing overall system complexity
Solution Approach 2:
The system changes the operational parameters by introducing a backup cryocooler that can be activated when the primary cryocooler fails. This parameter change (from single to dual cryocooler operation) extends the duration the system can withstand cooling interruptions while maintaining acceptable complexity through modular design
2Ease of repair
If cooling is interrupted for cryocooler replacement or servicing, then maintenance can be performed, but superconducting operation must be discontinued resulting in extended downtime
Solution Approach 1:
The dual-loop cooling system with independent cryocoolers enables one unit to be serviced while the other maintains superconducting operation. This segmentation of cooling functions allows maintenance activities without complete system shutdown, reducing downtime while keeping the overall system architecture manageable
Solution Approach 2:
The backup cryocooler serves as a pre-prepared cushion that activates when the primary cryocooler requires maintenance. This beforehand cushioning ensures continuous cooling capability during service operations, preventing operational discontinuation and minimizing time loss
3Stability of the object's composition
If a non-operating coldhead remains in the system during power outage, then the cooling system structure is maintained, but thermal short introduces additional heat to the superconducting system
Solution Approach 1:
The non-operating coldhead is physically extracted or isolated from the cooling loop during power outages or maintenance periods. This removal eliminates the thermal short pathway that would otherwise introduce harmful heat to the superconducting system, while the system structure remains intact through the presence of the backup cryocooler
Solution Approach 2:
The potential harm of having a non-operating coldhead creating thermal shorts is converted into benefit by using the backup cryocooler to compensate. The backup unit's operation masks the thermal leakage effects, transforming the problematic structural configuration into an acceptable state through active compensation
4Reliability
If the ride-through period is extended to allow for problem detection and correction, then superconducting operation can be maintained, but the cooling system complexity increases
Solution Approach 1:
The cooling system is segmented into redundant modular units that can operate independently. This segmentation enables extended ride-through capability through failover to the backup cryocooler while maintaining reasonable overall system complexity through standardized modular components and simplified control logic
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 dual-cryogen system effectively extends the ride-through period, allowing for timely detection and correction of issues, reduces helium boil-off, and prevents superconducting magnet quenching, enabling faster magnet cool-down and quicker system recovery.
Implementation Method 1
Magnetic resonance imagine (MRI) machines work by generating a very strong magnetic field using a superconducting magnet which consists of many coils or windings of wires through which a current is passed. Creating a strong magnetic field is accomplished using superconductivity, which involves reducing the resistance in the current-carrying conductors to practically zero by cooling them to ultra-low temperatures below the superconducting limits
Implementation Method 2
The second cooling loop also containing the first cryogen. The second cooling loop is in thermal communication with an enclosure containing a second cryogen, and is configured to cool the second cryogen within the enclosure
Implementation Method 3
an enclosure defining a thermal battery, the thermal battery containing a second cryogen and being in thermal communication with the magnet coils
Data Source
AI summary
A cooling system includes a first cooling loop containing a first cryogen, the first cooling loop being in thermal communication with a superconducting magnet and being configured to provide primary cooling for the magnet and a second cooling loop also containing the first cryogen. The second cooling loop is in thermal communication with an enclosure containing a second cryogen and is configured to cool the second cryogen within the enclosure. The enclosure is in thermal communication with the superconducting magnet and is configured to provide secondary cooling for the magnet.