Multi-refrigerator high speed cryopump
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Solution Overview
Problem
Conventional cryopumps face limitations in size due to thermal load constraints, leading to reduced pumping speed and increased weight and cost, as they rely on single refrigerators that struggle to manage temperature differentials effectively across large surfaces.
Innovation Solution
A cryopump design utilizing a thermal coupling between a two-stage and a single-stage refrigerator, with a base plate having varying cross-sectional areas and thermal conductance rods to distribute heat uniformly, allowing for controlled heat leakage and maintaining temperature differences between refrigerators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional single-refrigerator cryopumps use high conductivity materials and increased cross-sectional area of radiation shielding to reduce temperature differential, then the temperature differential across the thermal path is reduced, but the weight and cost increase and the cool down time and regeneration time increase
Solution Approach 1:
The single refrigerator system is segmented into a two-stage refrigerator (with first and second stages) and a single-stage refrigerator, where each stage is strategically positioned to cool different components. The two-stage refrigerator's first stage cools the radiation shield while the second stage cools the primary pumping surface, and the single-stage refrigerator provides additional cooling capacity. This segmentation allows efficient heat management without requiring excessive thermal conduction materials.
Solution Approach 2:
The invention introduces a vertical stacking dimension by placing the single-stage refrigerator above the two-stage refrigerator within the same thermal envelope. This multi-level arrangement allows heat loads from different temperature zones to be managed independently, reducing the need for horizontal thermal conduction paths that would require heavy shielding materials.
2Temperature
If conventional cryopumps increase the mass of radiation shielding to reduce temperature differential, then the temperature gradient is reduced, but the cool down time and regeneration time increase
Solution Approach 1:
The cooling system is segmented into multiple independent refrigerator stages, allowing each stage to be optimized for its specific temperature range. The first stage of the two-stage refrigerator handles the warmer radiation shield cooling, while the second stage handles the colder primary pumping surface, enabling faster thermal response without the thermal inertia of massive shielding.
Solution Approach 2:
The multi-stage refrigerator configuration is pre-configured to provide staged cooling capacity, where the first stage can be activated to pre-cool the radiation shield before the second stage engages for primary surface cooling. This preliminary action reduces the overall cool-down time by preparing thermal conditions in advance.
3Temperature
If conventional cryopumps use high conductivity materials in radiation shields to reduce temperature differential, then the thermal conductance increases, but the weight and cost increase
Solution Approach 1:
The radiation shielding thermal management is segmented into multiple independent cooling zones, each served by appropriate refrigerator stages. This eliminates the need for a single massive high-conductivity thermal path, as each zone can be cooled independently with lower conductivity materials.
Solution Approach 2:
The invention introduces intermediate cooling stages (the first stage of the two-stage refrigerator and the single-stage refrigerator) that act as thermal mediators between the environment and the primary pumping surface. These intermediaries reduce the thermal burden on the radiation shield, allowing lighter shielding materials to be used.
4Quantity of substance
If conventional single-refrigerator systems operate at higher temperatures to accept higher heat loads, then the heat load capacity increases, but the pumping speed and efficiency decrease
Solution Approach 1:
The heat load management is segmented across multiple refrigerator stages operating at different temperature levels. The first stage of the two-stage refrigerator operates at a higher temperature to accept higher heat loads from the radiation shield, while the second stage operates at lower temperature for the primary pumping surface, maintaining high pumping speed. The single-stage refrigerator provides additional heat load capacity.
Solution Approach 2:
The invention adds a vertical temperature dimension by stacking refrigerator stages at different temperature levels, allowing simultaneous handling of high heat loads at warmer temperatures and high-speed pumping at colder temperatures, resolving the trade-off between heat load capacity and pumping speed.
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 enhances refrigeration capability, maintains uniform frost growth, and reduces weight while increasing pumping speed and efficiency, enabling larger cryopumps to handle high vacuum environments effectively.
Implementation Method 1
a base plate having varying cross-sectional areas and thermal conductance rods to distribute heat uniformly
Implementation Method 2
a cryogenically cooled radiation shield surrounds the primary pumping surface and provides radiation shielding
Implementation Method 3
high boiling point gases, such as water vapor, are condensed on the frontal array
Implementation Method 4
an adsorbent, such as activated carbon, is placed on portions of these primary pumping surfaces to adsorb gases
Implementation Method 5
The cryopumps comprise a low temperature surface called a primary pumping surface, which operates in the temperature range of 4 to 25 Kelvin (K)
Data Source
AI summary
A refrigerator system or cryopump includes a first refrigerator having at least first and second stages, and a second refrigerator. A thermal coupling between the first stage of the first refrigerator and a cold end of the second refrigerator is restricted to maintain a temperature difference between the cold end of the second refrigerator and the first stage of the first refrigerator. The refrigerator system or cryopump also includes a radiation shield in thermal contact with the cold end of the second refrigerator, and a condensing surface, spaced from and surrounded by the radiation shield, and in thermal contact with a second stage, e.g., coldest stage, of the first refrigerator. The restricted thermal coupling can be configured to balance the cooling load on the two refrigerators.