Cryopump Hybrid Frontal Array for Radiation Shielding and Flow Control
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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 low radiation energy on the second stage array, as existing louvers provide good radiation shielding but restrict gas flow, and orifice plates enhance flow control but reduce pumping speeds.
Innovation Solution
A hybrid frontal array combining louvers and orifice plates, where louvers occupy the center region and an orifice plate surrounds them, allowing adjustable flow control and radiation management, with orifices that can be plugged to adjust pumping speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If louvers are used in the frontal array, then radiation shielding is improved, but gas flow control is worsened
Solution Approach 1:
The patent combines louvers and orifice plates into a hybrid frontal array structure. The louvers provide radiation shielding while the orifice plates provide precise gas flow control. This merging of two different components resolves the contradiction by allowing both radiation protection and flow control to function simultaneously in the same structure.
2Ease of operation
If orifice plates are used in the frontal array, then gas flow control is improved, but pumping speed is worsened
Solution Approach 1:
The patent applies different structures (louvers vs. orifice plates) to different regions of the frontal array based on local requirements. The orifice plates are positioned where precise flow control is needed, while louvers are positioned where radiation shielding is the primary concern. This local differentiation allows the system to achieve both flow control and acceptable pumping speed by optimizing each region's function.
3Object-affected harmful factors
If a solid plate is used in the frontal array, then radiation shielding is improved, but gas flow is worsened
Solution Approach 1:
The patent segments the frontal array into multiple components (louvers and orifice plates) rather than using a single solid plate. The louvers are segmented structures that provide radiation shielding while maintaining gas flow pathways. The orifice plates are segmented with multiple small holes that control flow while shielding radiation. This segmentation resolves the contradiction by creating a structure that is neither fully solid nor fully open.
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 achieves pumping speeds comparable to louver arrays with the flow control of orifice plates, maintaining low radiation energy on the second stage array and allowing adjustable pumping speeds for Type II and Type III gases.
Implementation Method 1
In operation, high boiling point gases such as water vapor are condensed on the frontal array
Implementation Method 2
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
Implementation Method 3
This surface is surrounded by a high temperature radiation shield usually operated in the temperature range of 40-130 K, which provides radiation shielding to the lower temperature array
Data Source
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.