Cryogenic Transfer Chamber for DNP Sample Introduction
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Solution Overview
Problem
Conventional cryogenic systems for dynamic nuclear polarization face challenges in maintaining low temperatures and helium volume due to the introduction of warm samples, leading to limited sample processing capacity and cryogen wastage.
Innovation Solution
A method and apparatus that direct heat from introduced materials away from the liquid helium bath to a cooling unit using a thermally linked equilibrator and cooling unit, minimizing thermal impact on the cryogenic system through conductive and convective cooling techniques, allowing for successive sample positioning and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If warm samples are introduced into the liquid helium bath for cooling and polarization, then the samples can be cooled to cryogenic temperatures, but the temperature of the helium bath increases and helium volume is lost
Solution Approach 1:
The patent introduces a cryogenic transfer chamber as an intermediary component between the ambient environment and the liquid helium bath. This transfer chamber is cooled by the sorption pump to cryogenic temperatures and serves as an intermediate cooling stage. Samples are first cooled in the transfer chamber before being introduced into the liquid helium bath, thereby reducing the thermal load on the bath and minimizing helium consumption.
2Temperature
If the pressure above the helium bath is reduced to achieve low temperatures, then the bath temperature decreases to enable DNP, but mechanical pumps expel helium into the ambient environment causing cryogen loss
Solution Approach 1:
The patent replaces mechanical vacuum pumps with a sorption pump that uses adsorption physics instead of mechanical expulsion. The sorption pump contains cold traps or sorbent materials that adsorb helium atoms from the vapor phase, creating vacuum conditions without mechanically expelling helium into the environment. This eliminates the primary source of helium loss while maintaining the necessary low pressure for cryogenic temperatures.
Solution Approach 2:
The sorption pump utilizes phase transition and adsorption phenomena where sorbent materials (such as activated charcoal or other porous materials) transition from a neutral state to an adsorbed state, capturing helium atoms from the vapor phase. This phase-based mechanism allows for vacuum generation without mechanical helium expulsion, thereby preventing cryogen loss.
3Loss of substance
If a sorption pump is used to reduce pressure without losing cryogen volume, then helium can be conserved and operational period extended, but the volume of liquid helium generated is limited by geometric considerations
Solution Approach 1:
The patent implements preliminary cooling action by using the sorption pump to pre-cool the transfer chamber and samples before they interact with the main liquid helium bath. This preliminary cooling reduces the thermal load on the bath, allowing the limited liquid helium volume to be used more efficiently for actual polarization operations rather than compensating for repeated thermal disturbances.
4Quantity of substance
If the mass of charcoal and physical size of the container are increased to generate more liquid helium, then the volume of liquid helium increases, but the device complexity and size increase
Solution Approach 1:
The patent segments the cooling function into two distinct components: the sorption pump for vacuum generation and the transfer chamber for intermediate cooling. This segmentation allows the sorption pump to be optimized for its specific function without needing to be oversized for liquid helium generation, while the transfer chamber handles the cooling of samples. The system achieves efficient use of limited liquid helium through functional segmentation rather than increasing overall device size.
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 reduces the impact on the helium bath temperature, enabling increased sample processing capacity and efficient cryogen conservation by directing heat loads to the cooling unit rather than the liquid helium, thus extending the operational period and reducing helium consumption.
Implementation Method 1
This sorption pump contains a charcoal-based sorbent that absorbs gaseous helium at low temperatures
Implementation Method 2
directing heat from the introduced material away from the liquid helium bath and to a cooling unit
Implementation Method 3
minimizing thermal impact on the cryogenic system through conductive and convective cooling techniques
Implementation Method 4
These low temperatures are typically achieved by reducing the pressure above a volume of liquid helium
Data Source
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AI summary
Provided is an apparatus and method for introducing a sample into a cryogenic system (70) comprising, an airlock chamber (20), a sample path (10) having a first end connected to the airlock chamber and a second end connected to a cryogenic helium bath, an equilibrator (60), inserted into the sample path and positioned between the airlock and the cryogenic bath (72) and which allows for passage of a sample to the cryogenic helium bath, and a cooling unit to coupled to the equilibration to control the temperature of the equilibrator. A machine-readable medium, comprising instructions which when executed by a controller causes a sample to be positioned within the cryogenic system, is also provided.