Remote NMR Refrigerator Layout for Low-Interference Cryogenic Cooling
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Solution Overview
Problem
Conventional NMR spectrometers face inefficiencies and disturbances due to the integration of refrigerators within the magnet cryostat, leading to suboptimal cooling and significant power loss, as well as magnetic and mechanical interference.
Innovation Solution
A common refrigerator system with a cold head and heat exchangers is placed in a separate, thermally insulated housing, with insulated transfer lines connecting to the cryostat and NMR probe head, allowing for efficient cooling power utilization and minimizing disturbances by externalizing the refrigerator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the refrigerator is installed inside the magnet cryostat, then the cooling structure is more compact, but magnetic and mechanical disturbances are generated and cooling efficiency decreases
Solution Approach 1:
The refrigerator is extracted from the magnet cryostat and placed in a separate housing, removing the source of magnetic and mechanical disturbances from the NMR measurement environment while maintaining the cooling function through external connection via transfer lines
2Volume of moving object
If the refrigerator is installed inside the magnet cryostat, then the structure is more compact, but cooling efficiency and power utilization are reduced
Solution Approach 1:
Transfer lines serve as intermediaries to transport cooled coolant from the external refrigerator to the NMR probe head and magnet cryostat, enabling efficient cooling without direct installation inside the magnet cryostat, thereby improving power utilization efficiency
3Object-affected harmful factors
If the refrigerator is placed in a separate housing, then magnetic and mechanical disturbances are minimized, but the device complexity increases
Solution Approach 1:
The cooling system is segmented into separate functional modules: the refrigerator unit in one housing, the magnet cryostat in another, connected by transfer lines. This modular segmentation reduces interference while maintaining system functionality
4Loss of energy
If the refrigerator is placed in a separate housing, then power loss is reduced, but the heat exchanger arrangement flexibility is constrained by transfer line connections
Solution Approach 1:
The system allows adjustment of operating parameters such as coolant flow rate, temperature, and pressure to optimize cooling efficiency while compensating for the constraints imposed by transfer line connections, achieving high power utilization efficiency
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 power loss by up to 100%, minimizes mechanical and magnetic interference, and allows for more flexible heat exchanger arrangement, enhancing the effectiveness and cost-effectiveness of the cooling process.
Implementation Method 1
The thermal loss caused by thermal conduction and thermal radiation is therefore a problem
Implementation Method 2
The thermal loss caused by thermal conduction and thermal radiation is therefore a problem
Implementation Method 3
Heat exchangers and a transfer line from the refrigerator to the NMR probe head transfer the cooling power generated by the refrigerator
Implementation Method 4
The cooled components of the probe head are usually at temperatures of 10 to 60 Kelvin. A Gifford-MacMahon cooler (GM) or pulse tube cooler (PT) is e.g. used as refrigerator
Implementation Method 5
one or more radiation shields surrounding the helium tank, an outer vacuum container which is subsequently referred to as the outer shell, and one or more neck tubes which connect the helium tank to the outer shell. The radiation shields may also be containers which are filled with liquid nitrogen (77.3 K) to reduce the heat input into the helium tank
Data Source
AI summary
An NMR spectrometer comprising a magnet coil system disposed in the helium tank (8) of a cryostat and an NMR probe head (4) which is disposed in a room temperature bore of the cryostat and contains a cooled RF resonator (13) for receiving NMR signals from a sample to be examined, wherein the helium tank (8) and the NMR probe head (4) are cooled by a common, multi-stage, compressor-operated refrigerator, is characterized in that the common refrigerator comprises a cold head (6) and several heat exchangers (21, 24, 25, 28, 31, 33, 34) at different temperature levels, wherein the refrigerator is disposed at a spatial separation from the cryostat in a separate, evacuated and thermally insulated housing (5), and several cooling circuits (1a, 1b, 1c, 1d, 2a, 2b, 3a, 3b) having thermally insulated transfer lines (14a, 14b, 15) are provided between the housing (5) containing the heat exchangers (21, 24, 25, 28, 31, 33, 34) and the cryostat, and also between the housing (5) and the NMR probe head (4). The probe head and magnet cryostat of the inventive NMR spectrometer can thereby be cooled by a common refrigerator, wherein the cooling resources of the used refrigerator are optimally utilized.