Cryogen free cooling apparatus and method
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Solution Overview
Problem
Cryogen-free cooling systems face challenges in efficiently loading warm samples into cold cryostats without warming the entire system, due to sealed vacuum vessels, radiation shields, and the absence of liquid cryogens for pre-cooling, as well as the need for remote electrical contacts.
Innovation Solution
The apparatus utilizes multiple radiation shields within the vacuum chamber to pre-cool samples before reaching the working region, employing rotatable elongate probes with thermal connectors and closure systems to minimize heat transfer, and allows for flexible thermal connections using screw threads, springs, or cone-shaped mating parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a warm sample is loaded directly into a cold cryostat without pre-cooling, then the sample change process is simple and fast, but thermal shock damages the sample and equipment
Solution Approach 1:
The patent implements pre-cooling of the sample before it enters the cold region by introducing it through a passage that allows thermal contact with the cold wall at a controlled intermediate stage. This preliminary cooling action prevents thermal shock when the sample finally reaches the cold mounting body, while maintaining relatively fast sample change capability.
2Ease of operation
If the entire cryostat system is warmed up to change samples, then sample loading is simple, but the cooling time increases significantly
Solution Approach 1:
The patent divides the cryostat into distinct thermal zones: a warm region for sample loading, a cold region for sample mounting, and an intermediate passage connecting them. The passage itself acts as a thermal transition zone. This segmentation allows sample changes without warming the entire system, as only the passage needs to be thermally managed during the transition.
3Object-affected harmful factors
If liquid cryogens are used for pre-cooling samples, then thermal shock is reduced, but the system becomes dependent on cryogen reservoirs
Solution Approach 1:
The patent utilizes the cold wall of the cryostat itself as the cooling medium for the passage. The cold wall naturally provides the cooling effect without requiring separate cryogen reservoirs or liquid cryogen circulation systems. The passage is thermally coupled to the cold wall, allowing it to self-cool as samples pass through, eliminating dependency on additional cryogen management infrastructure.
4Loss of energy
If the passage for sample introduction is thermally isolated, then heat load is reduced, but sample pre-cooling is insufficient
Solution Approach 1:
The patent applies different thermal characteristics to different parts of the passage. The passage wall in contact with the cold region provides thermal cooling to the sample, while the outer surface may be thermally isolated from the warm environment. This local differentiation of thermal properties allows the passage to cool samples effectively where needed while minimizing overall heat load from the warm region.
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
Enables efficient sample loading into cryogen-free cooling systems by pre-cooling samples using radiation shields, reducing thermal shock and heat transfer, and allowing for remote electrical connections, thereby speeding up the sample change process without warming the entire system.
Implementation Method 1
the sample is entered into the equipment at room temperature, typically around 300K and then moved to another position where thermal contact is made with a body at a much lower temperature
Implementation Method 2
thermal contact is made with a body at a much lower temperature which in some systems can be lower than 1K
Implementation Method 3
the internals of the system are usually contained within a sealed vacuum vessel to reduce heat load
Implementation Method 4
within that sealed vacuum vessel, the sample space is usually enclosed by one or more radiation shields to further reduce the heat load
Data Source
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AI summary
A cryogen free cooling apparatus comprises at least one heat radiation shield (54) surrounding a working region (20) and located in a vacuum chamber (4). A cryogen free cooling system has a cooling stage coupled to the heat radiation shield (54). Aligned apertures (56,58) are provided in the heat radiation shield and vacuum chamber walls. Sample loading apparatus has a sample holding device (2) attached to one or more elongate probes (3) for inserting the sample holding device through the aligned apertures (56,58) to the working region (20); and a thermal connector enables the sample holding device to be releasably coupled for heat conduction via said connector to a cold body or cold bodies within the vacuum chamber so as to pre-cool a sample on or in the sample holding device.