NMR Probe Head Cooling Using a Shared Cryogenic Helium Circuit
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Solution Overview
Problem
Conventional NMR spectrometer systems face inefficiencies in cooling the NMR probe head and magnet cryostat, leading to significant power loss and risk of heat input causing magnet quenching, due to suboptimal utilization of cooling resources and complex cooling setups.
Innovation Solution
A common refrigerator's cold head is positioned in a neck tube connecting the outer shell to the helium tank, with thermally insulated transfer lines forming a helium space that uses cryogenic helium as coolant, allowing for multiple temperature levels and eliminating the need for additional coolants and heat exchangers, while maintaining the flexibility to adjust temperature levels for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common refrigerator is used to cool both the magnet cryostat and the NMR probe head, then device complexity is reduced, but cooling efficiency deteriorates due to inability to provide multiple temperature levels
Solution Approach 1:
The patent segments the cooling system into multiple independent temperature levels by providing separate refrigeration units for the magnet cryostat and the NMR probe head. Each refrigeration unit can be optimized for its specific temperature requirements, allowing the magnet cryostat to be cooled to 4.2K while the NMR probe head is cooled to 20K or other intermediate temperatures, thereby resolving the contradiction between device simplicity and cooling efficiency.
2Ease of operation
If transfer lines extend within the cryostat for cleaning access, then ease of operation is improved, but reliability deteriorates due to risk of heat input causing magnet quenching
Solution Approach 1:
The patent extracts the NMR probe head from the magnet cryostat environment, placing it in a separate temperature zone accessible from the room temperature bore. This allows the probe head to be cleaned and maintained without exposing the magnet cryostat to heat input, as the probe head can be removed and serviced independently while the magnet remains isolated in its cryogenic environment, thus resolving the contradiction between operational ease and system reliability.
3Productivity
If a cold finger is installed directly in the magnet cryostat for direct cooling, then productivity is improved, but loss of substance worsens due to helium evaporation
Solution Approach 1:
The patent introduces an intermediary thermal isolation barrier between the cold finger and the magnet cryostat helium environment. This intermediary structure allows efficient heat transfer to the NMR probe head while preventing direct thermal coupling that would cause helium evaporation, thus resolving the contradiction between cooling productivity and helium conservation.
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 optimizes cooling efficiency, reduces power loss, and simplifies maintenance by allowing flexible temperature adjustments and minimizing the risk of clogging, thereby enhancing the overall performance and reliability of the NMR apparatus.
Implementation Method 1
Heat exchangers and a transfer line from the refrigerator to the NMR probe head transport the cooling power generated by the refrigerator
Implementation Method 2
at least one cooling circuit comprising thermally insulated transfer lines disposed between the helium space and the NMR probe head
Implementation Method 3
a common, multi-stage, compressor-operated refrigerator... which is cooled, together with the NMR probe head, by a cold head of a common, multi-stage, compressor-operated refrigerator
Data Source
AI summary
An NMR apparatus comprising a superconducting magnet coil system, in particular, an NMR spectrometer, with a cryostat which comprises an outer shell and a helium tank which contains the magnet coil system, and with an NMR probe head which is disposed in a room temperature bore of the cryostat and which contains a cooled RF resonator for receiving NMR signals from a sample to be examined and is cooled, together with the NMR probe head, by a cold head of a common, multi-stage, compressor-operated refrigerator, is characterized in that the cold head of the refrigerator is disposed in a neck tube, the upper end of which is connected to the outer shell of the cryostat and the lower end of which is connected to the helium tank in such a manner that the neck tube and the helium tank delimit a helium space, with at least one cooling circuit with thermally insulated transfer lines being provided between the helium space and the NMR probe head, wherein the cryogenic helium in the helium space is used as coolant for the cooling circuit. This produces an NMR apparatus which cools a plurality of elements at different temperature levels using only one single cryocooler to optimally utilize the cooling resources of the refrigerator.