Cryopump hybrid frontal array
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Solution Overview
Problem
Cryopump designs face challenges in achieving optimal pumping speeds for Type II and Type III gases while maintaining effective radiation shielding and flow control, leading to inefficiencies in gas capture and increased heat loads on the second stage array.
Innovation Solution
A hybrid frontal array design combining louvers and orifice plates, with adjustable orifices and flaps, provides a balance between gas transmission and deflection, allowing for adjustable pumping speeds and reduced radiation exposure to the second stage array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If orifice plates are used to restrict gas flow, then radiation shielding is improved, but pumping speed for Type II and Type III gases is reduced
Solution Approach 1:
The frontal array is segmented into multiple functional zones: outer orifice plates for radiation shielding, inner louvers for gas flow control, and a central open region for high-speed pumping. This segmentation allows each zone to optimize its specific function while working together as an integrated system.
Solution Approach 2:
Different regions of the frontal array have different structural properties tailored to local requirements: the outer regions use orifice plates for radiation blocking, the inner regions use louvers for selective gas flow, and the center remains open for maximum pumping speed. This local differentiation resolves the contradiction between shielding and pumping performance.
2Productivity
If louvers are used for radiation shielding, then pumping speed is maintained, but radiation shielding effectiveness is reduced compared to orifice plates
Solution Approach 1:
The design merges orifice plates and louvers into a single hybrid frontal array structure. The orifice plates provide radiation shielding while the integrated louvers maintain gas flow control, combining the advantages of both designs into one unified system that achieves both radiation protection and high pumping speed.
3Temperature
If the frontal array is made more opaque to radiation, then heat load on the second stage array is reduced, but gas flow control capability is reduced
Solution Approach 1:
The frontal array incorporates adjustable elements including removable plugs for orifices and adjustable louver configurations, allowing the system to dynamically adapt gas flow control while maintaining radiation shielding. This adjustability enables optimization for different operating conditions without sacrificing shielding effectiveness.
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 hybrid design enhances pumping speeds for Type II and Type III gases, maintains low heat loads on the second stage array, and allows for adjustable pumping speed by plugging orifices, improving gas capture capacity and reducing regeneration frequency.
Implementation Method 1
The frontal array which closes the radiation shield is cooled by the first stage heat sink through the shield or, as disclosed in U.S. Pat. No. 4,356,701, through thermal struts. The frontal array protects the second stage array to reduce radiant heat from striking the second stage
Implementation Method 2
The primary pumping surface, or cryopanel, is connected to a heat sink at the coldest end of the second stage of the cold finger. The radiation shield is connected to a heat sink, or heat station, at the coldest end of the first stage of the refrigerator
Implementation Method 3
To capture Type III gases, inner surfaces of the second stage array may be coated with an adsorbent such as activated carbon, 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
In operation, high boiling point gases such as water vapor are condensed on the frontal array. Type II gases, such as nitrogen, condense on the second stage array
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A cryopump comprises a refrigerator, a condensing array cooled by the refrigerator, a radiation shield surrounding the condensing array and cooled by the refrigerator. The radiation shield has a frontal opening covered by a frontal array that is also cooled by the refrigerator. The frontal array comprises louvers across an otherwise substantially open center region of the frontal opening and an orifice plate across an outer region of the frontal opening. The hybrid frontal array allows for pumping speeds approximating those of a louver frontal array but with flow control comparable to an orifice plate.