Cryopump with enhanced frontal array
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Solution Overview
Problem
Conventional cryopump designs face a trade-off between high gas conductance and low radiation loading on the second stage array, with existing solutions either increasing radiation load or reducing gas capture efficiency.
Innovation Solution
A modified cryopump configuration featuring a recessed, domed frontal array thermally coupled to the cold stage, wrapped around the primary cryopumping array, with louvers that focus gas conductance while minimizing radiation loading, allowing for a capture probability of hydrogen of at least 20% and reducing radiation load to less than 3%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional frontal array is used to shield the second stage array, then radiation loading on the second stage array is reduced, but gas conductance to the second stage array decreases
Solution Approach 1:
The frontal array is divided into multiple segments or zones with varying degrees of openness. Different portions of the array have different louver configurations, allowing optimization of radiation shielding in some areas while maintaining gas conductance in others. This segmented approach resolves the contradiction by allowing simultaneous radiation protection and gas flow pathways.
Solution Approach 2:
Different regions of the frontal array are designed with different properties - some areas have more open structures for gas conductance while others provide denser radiation shielding. The array transitions from a uniform structure to one with spatially varying characteristics, allowing local optimization of both radiation protection and gas flow.
2Productivity
If the second stage array diameter is reduced to increase gas conductance, then hydrogen capture probability increases, but the radiation shield becomes less effective
Solution Approach 1:
Instead of only reducing the second stage array diameter, the solution adds a new dimension - the frontal array structure - that provides radiation shielding in a different spatial configuration. This allows the second stage array to maintain an optimal size for gas capture while the frontal array provides the necessary radiation protection in front of it.
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 enhances gas capture efficiency while significantly reducing radiation loading on the second stage array, achieving improved vacuum performance and reduced contamination, suitable for next-generation implant applications with lower heat loading and charcoal contamination.
Implementation Method 1
high boiling point gases such as water vapor are condensed on the cold frontal array
Implementation Method 2
Lower boiling point gases pass through the frontal array and into the volume within the radiation shield. Type II gases, such as nitrogen, condense on the colder second stage array
Implementation Method 3
To capture Type III gases, inner surfaces of the second stage array may be coated with an adsorbent such as charcoal, zeolite or a molecular sieve. Adsorption is a process whereby gases are physically captured by a material held at cryogenic temperatures and thereby removed from the environment
Implementation Method 4
This surface is surrounded by a high temperature cylinder usually operated in the temperature range of 65-130 K, which provides radiation shielding to the lower temperature array
Data Source
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AI summary
A cryopump has a cryogenic refrigerator with a cold stage and a colder stage that cool a radiation shield (20) having sides, a closed end and a frontal opening (204). A primary cryopumping array (130) is thermally coupled to the colder stage, and a frontal array (206) is thermally coupled and cooled. The frontal array (206) is spaced from and wrapped around the frontally facing envelope of the primary cryopumping array (130), the frontal array (206) being recessed from the frontal opening (204) and closer to the primary cryopumping array (130) than to the frontal opening (204).