Cryogen-free magnet system comprising a magnetocaloric heat sink
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Solution Overview
Problem
Cryogen-free superconducting magnet systems have a short 'time to quench' when the cryocooler malfunctions, as they quickly heat up beyond operational temperatures, necessitating a solution to maintain cryogenic conditions without cryogenic fluids.
Innovation Solution
Incorporating a heat sink apparatus with magnetocaloric materials that absorb heat through the magnetocaloric effect, allowing the system to maintain cryogenic temperatures by drawing heat from its surroundings when demagnetized, and optimizing specific heat through magnetic field manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cryogen-free system is used to eliminate cryogenic fluids, then the system achieves true dry operation and avoids cryogen storage requirements, but the time to quench becomes very short when the cryocooler malfunctions
Solution Approach 1:
The patent pre-cools a thermal mass (such as a copper block or other high-heat-capacity material) to cryogenic temperatures before normal operation. This thermal mass acts as a pre-charged heat sink that can absorb ambient heat for an extended period when the cryocooler fails, thereby prolonging the time to quench while maintaining true cryogen-free operation.
Solution Approach 2:
The patent changes the thermal parameters of the system by introducing a thermal mass with high heat capacity and pre-cooling it to cryogenic temperatures. This parameter change enables the system to store thermal energy and extend the time to quench without requiring cryogenic fluids, thus resolving the contradiction between cryogen-free operation and extended time to quench.
2Duration of action of moving object
If small amounts of cryogen are stored in a reservoir to prolong time to quench, then the system maintains temperature during cooler malfunction, but the system is no longer truly cryogen-free and requires additional condensation equipment
Solution Approach 1:
The patent extracts the cryogen from the system entirely and replaces it with a thermal mass that can be pre-cooled to cryogenic temperatures. This extraction eliminates the need for cryogen storage reservoirs and condensation equipment while still achieving extended time to quench, thus resolving the contradiction between prolonged time to quench and maintaining cryogen-free operation.
Solution Approach 2:
The patent substitutes the mechanical system of cryogen storage and phase change with a thermal mass-based heat sink system. The thermal mass absorbs heat through conduction and heat capacity rather than through cryogen evaporation, eliminating the need for cryogen handling infrastructure while achieving the same temperature maintenance function.
3Temperature
If thermal coupling between the coil and cooler is reduced when the active cooler fails, then heat path to the superconducting magnet is minimized, but the system complexity increases with additional control mechanisms
Solution Approach 1:
The patent pre-cools a thermal mass to cryogenic temperatures before normal operation, creating a thermal buffer that passively absorbs ambient heat when the cryocooler fails. This preliminary action eliminates the need for active thermal coupling control mechanisms, as the thermal mass automatically absorbs heat without requiring sensors, actuators, or control logic, thus resolving the contradiction between temperature stability and device complexity.
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 significantly prolongs the 'time to quench' in a cryogen-free system, maintaining cryogenic conditions for an extended period even when active cooling fails, while minimizing external magnetic field interference and integrating with existing cryostat components.
Implementation Method 1
the heat sink apparatus includes magnetocaloric material. The heat sink apparatus is thermally connected to the superconducting magnet arrangement and/or to parts of the cryostat arrangement, through which ambient heat can flow to the magnet arrangement
Data Source
AI summary
A cryostat system is kept at a cryogenic operating temperature without providing or supplying cryogenic fluids by a cryocooler. The cryostat system includes a superconducting magnet arrangement and a heat sink apparatus to prolong the time before the superconducting magnet arrangement quenches/returns to the normally conducting state if active cooling fails. The heat sink apparatus includes magnetocaloric material and is thermally connected to the superconducting magnet arrangement and/or to parts of the cryostat system through which ambient heat can flow to the superconducting magnet arrangement. In this way, the cryostat system can be operated in a truly “cryogen-free” manner while maintaining a sufficiently long time to quench in the event of potential operational malfunctions.