Cryocooler Cooling Shroud for Molecular Beam Epitaxy
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Solution Overview
Problem
Current molecular beam epitaxy (MBE) techniques require expensive cryogenic fluids for cooling surfaces inside vacuum chambers, leading to safety hazards, frequent refills, and complex piping systems, which are inefficient and pose handling risks.
Innovation Solution
An apparatus and method utilizing a cryocooler, such as a Gifford-McMahon or pulse tube cryocooler, to cool surfaces within the vacuum chamber to cryogenic temperatures, eliminating the need for cryogenic fluids by integrating a vibration damping mechanism and thermal coupling for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cryogenic fluids are used to cool the shroud, then the shroud can be cooled to cryogenic temperatures for effective impurity trapping, but the system complexity increases due to required piping and storage tanks
Solution Approach 1:
The patent extracts the cryogenic fluid storage and piping system from the vacuum chamber environment. By using a cryocooler with a cold finger that extends through the chamber wall, the complex fluid handling system is moved outside the vacuum environment, eliminating the need for internal piping and storage tanks while maintaining effective cooling of the shroud to cryogenic temperatures
Solution Approach 2:
The cold finger acts as an intermediary thermal connection between the external cryocooler and the internal shroud. This mediator transfers cryogenic cooling capacity across the vacuum chamber boundary without requiring direct fluid contact or complex internal piping, simplifying the overall system architecture
2Temperature
If cryogenic fluids are used for cooling, then effective impurity trapping is achieved, but safety hazards arise from frostbite and asphyxiation risks
Solution Approach 1:
The hazardous cryogenic fluids are completely extracted from the vacuum chamber environment. The closed-cycle cryocooler operates externally, eliminating direct handling and presence of cryogenic liquids inside the chamber, thereby removing frostbite and asphyxiation hazards while maintaining the necessary cryogenic temperatures for impurity trapping
Solution Approach 2:
The closed-cycle cryocooler system operates autonomously without requiring manual refilling or handling of cryogenic fluids. The system self-regulates the cooling process, eliminating human interaction with hazardous materials while maintaining effective shroud cooling for impurity removal
3Quantity of substance
If cryogenic fluids are used to maintain low pressure, then impurity trapping is effective, but periodic refills are required due to boil-off
Solution Approach 1:
The closed-cycle cryocooler provides continuous, uninterrupted cooling operation without the periodic interruptions required by boil-off refills. The system maintains stable cryogenic temperatures indefinitely, ensuring continuous impurity trapping efficiency without time loss associated with refilling operations
Solution Approach 2:
The cryocooler system is self-sufficient and self-regulating, automatically maintaining the required cooling capacity without external intervention. The closed cycle eliminates the need for periodic refilling operations, making the system autonomous and eliminating time loss associated with maintenance refills
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 solution effectively traps impurities on the cooling shroud surfaces, maintaining low chamber pressure without the risks and costs associated with cryogenic fluids, enhancing the efficiency and safety of the MBE process.
Implementation Method 1
A cryocooler having at least a portion extending into the vacuum chamber is operatively coupled to the cooling shroud for extracting heat therefrom, and cooling the at least one surface of the cooling shroud to cryogenic temperatures
Implementation Method 2
At cryogenic temperatures, impurities condense and are trapped on the surface of the cooling shroud, reducing the pressure in the chamber. This effect is known as cryo-pumping
Implementation Method 3
the apparatus further comprises a vibration damping mechanism attaching the cryocooler to the enclosure
Data Source
AI summary
An apparatus and method for molecular beam epitaxy are described herein. The apparatus comprises an enclosure defining a vacuum chamber. A substrate holder is mounted within the vacuum chamber. At least one molecular beam source is in fluid communication with the vacuum chamber. A cooling shroud having at least one surface is mounted within the vacuum chamber spaced from the substrate holder. A cryocooler having at least a portion extending into the vacuum chamber is operatively coupled to the cooling shroud for extracting heat therefrom, and cooling the at least one surface of the cooling shroud to cryogenic temperatures.