Cryopump Inlet Flow Restrictor With Shielded Gas Paths
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Solution Overview
Problem
Conventional cryopump flow restrictor plates with direct line of sight to the cryopanel experience preferential gas pumping and increased radiant heat loads, leading to uneven frost build-up and shorter pressure recovery times in the chamber.
Innovation Solution
A two-stage flow restrictor design with an inlet component axially displaced from a shielding plate, using an intermediate component with angled apertures to divert gases around the shielding plate, preventing direct line of sight and promoting uniform gas flow and frost build-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional flow restrictor plates with direct line of sight orifices are used, then gas flow restriction is achieved, but preferential gas pumping and increased radiant heat loads occur
Solution Approach 1:
The patent introduces an intermediate shielding plate positioned between the orifices and the cryopanel. This shielding plate acts as a mediator that blocks the direct line of sight path, preventing radiant heat from reaching the cryopanel while still allowing gas flow through the orifices. The shielding plate is the intermediary element that resolves the contradiction between maintaining gas flow restriction and eliminating harmful radiant heat exposure.
2Ease of operation
If conventional flow restrictor plates with direct line of sight orifices are used, then gas flow restriction is achieved, but uneven frost build-up and preferential gas pumping occur
Solution Approach 1:
The shielding plate serves as an intermediary that redistributes gas flow patterns. By blocking direct line of sight, it prevents gas molecules from being channeled preferentially to specific areas of the cryopanel, thereby promoting more uniform frost build-up across the entire cryopanel surface while maintaining effective gas flow restriction.
3Productivity
If conventional flow restrictor plates are used, then pumping speed control is achieved, but pressure recovery time increases
Solution Approach 1:
The shielding plate eliminates preferential gas pumping pathways that cause localized frost accumulation and pressure fluctuations. By preventing direct line of sight, it ensures more uniform pressure distribution and frost build-up, which accelerates pressure recovery time after pump shutdown while maintaining pumping speed control through the orifices.
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 design reduces radiant heat loading, inhibits preferential gas pumping, and increases the time between regenerations by allowing more uniform gas capture and frost build-up on the cryopanel, enhancing the cryopump's performance and extending the interval between regenerations.
Implementation Method 1
A potential problem with plates having holes or orifices is that during viscous or continuous flow the orifices have a line of sight view of the second stage cryopanel in the pump and this increases radiant heat loads
Implementation Method 2
Type II gases are gases such as nitrogen that condense at the temperatures of the second stage cryopanels of a cryopump
Implementation Method 3
type III gases do not condense at these temperature and are generally captured by an adsorbent on the cryopanels
Data Source
AI summary
A flow restrictor for restricting a flow rate of gas flowing into a cryopump and the cryopump are disclosed. The flow restrictor is configured to be mounted in an inlet of the cryopump, the flow restrictor comprising: an inlet component for providing a gas flow path into the cryopump; a shielding plate mounted to at least partially obscure the gas flow path though the inlet component; and an intermediate component linking the shielding plate to the inlet component, the intermediate component comprising at least one aperture, the at least one aperture defining at least one gas flow path into the cryopump The shielding plate is configured to shield the gas flow path through the inlet component such that when mounted on the cryopump there is no direct line of sight path through the inlet component to a cryopanel within the cryopump.