Cryopump Radiation Cover Segmentation for Heat Load Reduction
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Solution Overview
Problem
Conventional cryopumps are inefficient in high-speed evacuation of non-condensable gases like hydrogen due to excessive heat load on the cryopanel assembly from radiant heat, which reduces pumping speed and increases refrigeration power wastage.
Innovation Solution
A cryopump design featuring a cryopanel assembly with adsorption areas on both surfaces, surrounded by a radiation shield and equipped with a radiation cover having a main plate that covers at least 80% of the cryopanel assembly's projection area and a louver portion, which shields radiant heat and directs gas molecules to the adsorption areas, reducing heat load without compromising pumping speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional radiation shield design is used, then the structure is simple, but excessive heat load is applied to the cryopanel assembly reducing pumping speed
Solution Approach 1:
The radiation cover is divided into two distinct functional portions: a main plate portion that directly shields the cryopanel assembly from radiant heat, and a louver portion that shields the gas receiving space while directing gas molecules toward the cryopanel assembly. This segmentation allows each portion to optimize its specific function, reducing overall heat load while maintaining pumping speed.
Solution Approach 2:
Different portions of the radiation cover are designed with different structures and orientations tailored to their specific locations and functions. The main plate portion is positioned to directly block radiant heat from reaching the cryopanel assembly, while the louver portion is angled to simultaneously block heat and guide gas flow. This local optimization resolves the contradiction between heat shielding and gas evacuation efficiency.
2Loss of energy
If the main plate covers more of the cryopanel assembly, then heat load is reduced, but the opening area for gas intake is reduced
Solution Approach 1:
The radiation cover is segmented into a main plate portion and a louver portion, each occupying different spatial zones. The main plate portion covers the central area to maximize heat shielding of the cryopanel assembly, while the louver portion is positioned at the periphery to preserve gas intake opening area. This spatial segmentation allows both heat reduction and adequate gas intake.
Solution Approach 2:
The louver portion acts as an intermediary structure that reconciles the conflict between heat shielding and gas intake. It is positioned to block radiant heat from reaching the gas receiving space while its open louver structure allows gas molecules to pass through and be directed toward the cryopanel assembly, effectively mediating between heat protection and gas flow requirements.
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
The design effectively suppresses unnecessary heat load on the cryopanel assembly, enhancing the high-speed pumping of non-condensable gases like hydrogen by shielding radiant heat and optimizing gas molecule path to adsorption areas, thus improving evacuation efficiency.
Implementation Method 1
A radiation cover disposed in a cryopump inlet... shields radiant heat... reducing heat load
Implementation Method 2
a cryopanel assembly including a plurality of cryopanels each having an adsorption area on both surfaces... performs vacuum evacuation by condensing gas
Data Source
AI summary
A cryopump includes: a cryopanel assembly including a plurality of cryopanels each having an adsorption area on both surfaces thereof; a radiation shield forming a gas receiving space that surrounds the cryopanel assembly; and a radiation cover disposed in a cryopump inlet. The radiation cover includes a main plate located at a position in the cryopanel inlet that corresponds to the cryopanel assembly and a louver portion located at a position in the cryopanel inlet that corresponds to the gas receiving space. The radiation cover may not include the louver portion.