Cryogen-Free Sample Loading with Radiation Shield Pre-Cooling
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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
A sample loading apparatus utilizing heat radiation shields within the vacuum chamber to pre-cool samples before reaching the working region, with multiple shields at different temperatures and flexible thermal connection mechanisms like screw threads and spring contacts to minimize heat transfer and facilitate efficient sample transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a sealed vacuum vessel with radiation shields is used to maintain cold environment, then heat load is reduced and cold environment is maintained, but sample pre-cooling cannot be performed without warming the entire system
Solution Approach 1:
The sample is pre-cooled in a pre-cooling chamber before being transferred to the cold mounting body. This preliminary cooling action reduces the thermal shock and allows rapid sample changes without warming the entire cryostat system.
Solution Approach 2:
The vacuum vessel is segmented into distinct zones: a pre-cooling chamber and a cold mounting body region, separated by a transfer mechanism. This segmentation allows independent temperature control in each zone, enabling sample pre-cooling without affecting the main cold environment.
2Object-affected harmful factors
If liquid cryogens are used to pre-cool samples during transfer, then thermal shock is reduced, but the system becomes dependent on liquid cryogen reservoirs and complex delivery mechanisms
Solution Approach 1:
A thermally conductive probe or rod acts as an intermediary between the pre-cooling chamber and the sample. This intermediary transfers heat efficiently during pre-cooling without requiring liquid cryogen delivery mechanisms, simplifying the system while still reducing thermal shock.
Solution Approach 2:
The liquid cryogen delivery system is replaced with a solid-state thermal conduction mechanism using thermally conductive materials in the probe and pre-cooling chamber. This mechanical substitution eliminates the need for complex liquid handling while achieving the same thermal shock reduction effect.
3Ease of operation
If the entire system is warmed to change samples, then sample access is simplified, but the cooling time and energy consumption increase significantly
Solution Approach 1:
Samples are pre-cooled in a dedicated pre-cooling chamber before transfer to the cold mounting body. This preliminary action maintains the main system at cold temperature while enabling rapid sample changes, eliminating the need to warm the entire system.
Solution Approach 2:
The pre-cooling function is extracted from the main cold environment and placed in a separate pre-cooling chamber. This extraction allows sample preparation and cooling to occur independently without affecting the main cryogenic system, reducing both cooling time and energy consumption.
4Reliability
If remote electrical contacts are made to the sample during loading, then vacuum seal is maintained, but the complexity of electrical connection increases
Solution Approach 1:
A probe with integrated electrical contacts serves as an intermediary, providing both mechanical support and electrical connection during sample transfer. This single intermediary component simplifies the system compared to separate mechanical and electrical connection mechanisms.
Solution Approach 2:
The mechanical support function and electrical connection function are merged into a single probe assembly. This combination reduces the number of separate components and simplifies the overall system while maintaining vacuum seal integrity.
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 rapid and efficient sample loading into cryogen-free cooling systems by pre-cooling samples using existing radiation shields, reducing thermal shock and maintaining the cold environment, thus speeding up the sample change process without warming the entire system.
Implementation Method 1
utilizing a cold body within the vacuum chamber to pre-cool a sample before the sample reaches the working region... utilize the heat radiation shield already present
Implementation Method 2
flexible thermal connection mechanisms like screw threads and spring contacts to minimize heat transfer and facilitate efficient sample transfer
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.