Cryopump Non-Contact Cap Member Design
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Solution Overview
Problem
Cryopumps face limitations in gas storage capacity due to condensed gas layers coming into contact with radiation shields or other components, leading to increased pressure and reduced vacuum chamber evacuation efficiency.
Innovation Solution
The design includes a cryocooler with a high-temperature and low-temperature cooling stages, a radiation shield, a non-contact cap member, and a low-temperature cryopanel configuration that prevents condensate contact with the tip stage surface, enhancing gas storage capacity by maintaining a non-contact thermal coupling and widening the empty space for condensate accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cryopump operates for extended periods, then gas storage capacity increases, but condensed gas layers come into contact with radiation shields causing vaporization and pressure increase
Solution Approach 1:
The patent introduces a non-contact cap member as an intermediary element between the radiation shield and the low-temperature cooling stage. This cap member prevents direct contact between condensed gas layers and the radiation shield, eliminating the harmful vaporization effect while allowing the cryopump to maintain extended gas storage capacity.
Solution Approach 2:
The patent adds a spatial dimension by positioning the low-temperature cooling stage axially beyond the radiation shield, creating a non-contact configuration. This dimensional arrangement allows condensed gas to be accommodated in the extended space without contacting the radiation shield, preventing vaporization while maintaining storage capacity.
2Length of moving object
If the axial distance between radiation shield and low-temperature cooling stage is reduced, then device length decreases, but empty space for condensate accommodation is reduced
Solution Approach 1:
The patent employs a nested configuration where the non-contact cap member is positioned within the space between the radiation shield and the low-temperature cooling stage. This nesting allows the condensate accommodation space to be utilized efficiently without increasing the overall device length, as the cap member is integrated into the existing axial structure.
3Use of energy by stationary object
If the non-contact cap member is thermally coupled to the high-temperature cooling stage, then thermal management is improved, but heat transfer to the low-temperature stage must be controlled
Solution Approach 1:
The non-contact cap member serves as a thermal intermediary, being thermally coupled to the high-temperature cooling stage while maintaining a controlled thermal boundary with the low-temperature stage. This allows efficient thermal management of the high-temperature stage while preventing excessive heat transfer to the low-temperature stage, maintaining the required temperature differential.
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 improves the storage limit of the cryopump by preventing vaporization of condensed gas and allowing for increased gas storage, thereby enhancing the evacuation efficiency of the vacuum chamber.
Implementation Method 1
A cryopump is a vacuum pump which captures gas by condensing or adsorbing the gas on a cryopanel cooled to a cryogenic temperature
Implementation Method 2
A cryopump is a vacuum pump which captures gas by condensing or adsorbing the gas on a cryopanel cooled to a cryogenic temperature
Implementation Method 3
a radiation shield which is thermally coupled to the high-temperature cooling stage
Implementation Method 4
a non-contact cap member which surrounds the axial tip stage surface in a non-contact manner and is thermally coupled to the high-temperature cooling stage
Data Source
AI summary
A cryopump includes a cryocooler which includes a first cooling stage, a second cooling stage having a tip stage surface, and a cryocooler structure portion which extends in an axial direction from the first cooling stage to the second cooling stage, a radiation shield which is thermally coupled to the first cooling stage and includes a shield front end which defines a shield main opening and a shield bottom portion having a cryocooler insertion hole which receives the cryocooler structure portion such that the tip stage surface faces the shield main opening, a cap member which surrounds the tip stage surface in a non-contact manner and is thermally coupled to the first cooling stage, and a second stage cryopanel which is disposed between the cap member and the first cooling stage in the axial direction and is thermally coupled to the second cooling stage.