Cryopump Radiation Shield Slit Design for Uniform Condensing Layer Growth
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Solution Overview
Problem
Cryopumps face limitations in gas capacity due to uneven growth of condensing layers on cryopanels, leading to increased pressure and reduced vacuum pumping efficiency when the condensing layer contacts the radiation shield or first cryopanel.
Innovation Solution
The design includes a radiation shield with a shield main slit and auxiliary slits that equalize the growth speed of condensing layers on multiple cryopanels by adjusting the gas inlet sizes and positions, allowing for non-contact arrangement of cryopanels with the radiation shield and maximizing the use of internal space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple cryopanels are arranged in the shield cavity, then the gas capacity limit is increased, but the condensing layer growth becomes uneven causing pressure increase and reduced pumping efficiency
Solution Approach 1:
The patent applies local quality by providing different inlet configurations at different locations of the shield cavity. The shield cavity is divided into multiple regions with different inlet areas, allowing each cryopanel to receive gas at appropriate rates. This creates localized gas flow control to match the condensing capacity of each cryopanel surface, preventing both underutilization and overloading of specific regions.
Solution Approach 2:
The patent segments the shield cavity into multiple independent gas inlet regions, each with its own controlled gas flow. By dividing the cavity into segments with different inlet configurations, the system can independently control gas distribution to multiple cryopanels, ensuring uniform condensing layer growth across all panels while maximizing total gas capacity.
2Volume of stationary object
If cryopanels are arranged close to the radiation shield to maximize space utilization, then the accommodation volume is increased, but the condensing layer contacts the radiation shield causing gas vaporization and pressure increase
Solution Approach 1:
The patent utilizes the axial dimension by arranging cryopanels at different axial positions within the shield cavity. The first cryopanel is positioned with its rear surface facing the radiation shield, while the second cryopanel is positioned axially below it. This vertical stacking in the axial dimension allows maximum space utilization without causing condensing layer contact with the radiation shield, as each panel has dedicated space below it for condensing layer accumulation.
Solution Approach 2:
The patent implements a nested arrangement where the second cryopanel is positioned within the shadow region created by the first cryopanel and the radiation shield. The second cryopanel is axially below the first cryopanel and radially positioned to utilize the remaining space in the shield cavity. This nested configuration maximizes the use of internal space while maintaining sufficient separation to prevent harmful contact between the condensing layer and the radiation shield.
3Quantity of substance
If the shield cavity is designed with large volume to increase gas capacity, then the accommodation volume is increased, but the condensing layer growth rate becomes uneven across different regions
Solution Approach 1:
The patent applies local quality by providing different inlet configurations at different locations of the shield cavity. The shield cavity is divided into multiple regions with different inlet areas, allowing each cryopanel to receive gas at appropriate rates. This creates localized gas flow control to match the condensing capacity of each cryopanel surface, preventing both underutilization and overloading of specific regions.
Solution Approach 2:
The patent changes the gas flow parameters by providing multiple inlets with different opening areas. The first inlet has a different opening area than the second inlet, allowing differential gas flow rates to be supplied to different cryopanels. This parameter adjustment ensures that gas is distributed according to the local condensing capacity requirements, maintaining uniform condensing layer growth across the entire shield cavity volume.
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 the gas capacity limit of the cryopump by ensuring uniform condensing layer growth and maximizing the accommodation volume, thereby improving the efficiency of vacuum pumping.
Implementation Method 1
A cryopump is a vacuum pump trapping gases on a cryogenically-cooled cryopanel by means of condensation or adsorption
Implementation Method 2
A cryopump is a vacuum pump trapping gases on a cryogenically-cooled cryopanel by means of condensation or adsorption
Implementation Method 3
a refrigerator that includes a high-temperature cooling stage and a low-temperature cooling stage
Implementation Method 4
The cryopump pumps gases from a vacuum chamber on which the cryopump is mounted
Data Source
AI summary
A cryopump includes a radiation shield, a top cryopanel, and a bottom cryopanel. The radiation shield includes a shield main slit that communicates a shield outside gap into a shield cavity. The top cryopanel includes a top cryopanel outer circumferential end located axially above the shield main slit. The bottom cryopanel includes a bottom cryopanel outer circumferential end located axially below the shield main slit. An annular vacant space is formed between the top cryopanel outer circumferential end and the bottom cryopanel outer circumferential end and the top cryopanel outer circumferential end is directly opposed to the bottom cryopanel outer circumferential end with the annular vacant space interposed therebetween.