Cryogenic Cooling System for High Average Power Laser Oscillators
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Solution Overview
Problem
Cryogenically-cooled laser amplifiers face limitations due to thermal effects such as film boiling, which reduces heat transfer efficiency and causes material deformations, limiting the average power of high-energy laser systems.
Innovation Solution
A cryogenic cooling system that directly contacts the laser amplifier material with a flowing cryogenically-cooled liquid, such as liquid oxygen, below its boiling point, using a heat exchanger and pump to maintain efficient heat transfer without film boiling, and a vacuum chamber to prevent condensation and ensure optimal cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct contact with boiling liquid nitrogen is used for cryogenic cooling, then cooling efficiency is improved, but film boiling occurs which reduces heat transfer efficiency and limits average power
Solution Approach 1:
The invention changes the temperature parameter of the cryogenic liquid from boiling point to sub-cooled temperature (below boiling point). This parameter change prevents film boiling while maintaining high heat transfer efficiency, thereby resolving the contradiction between cooling efficiency and heat transfer reliability
Solution Approach 2:
The invention applies preliminary cooling to the cryogenic liquid before it contacts the laser material, preventing the formation of vapor film in advance. By pre-cooling the liquid below its boiling point, the system anticipates and prevents film boiling, maintaining reliable heat transfer at high power levels
2Power
If soldering or thermal contact with copper heat sink is used, then heat removal is improved, but thermal expansion mismatch causes material deformations
Solution Approach 1:
The invention extracts the laser material from direct thermal contact with solid heat sinks (copper blocks). By removing the solid- solid thermal contact interface, the invention eliminates the thermal expansion mismatch problem that causes deformations, while maintaining effective heat removal through liquid cooling
Solution Approach 2:
The invention introduces a liquid cryogenic coolant as an intermediary between the heat source and the cooling system. This liquid mediator provides thermal contact without the rigid thermal expansion constraints of solid-to-solid contact, preventing deformation while enabling heat removal
3Temperature
If materials are placed between laser material and cooling source, then thermal contact is improved, but temperature increases due to conduction within the heat sink
Solution Approach 1:
The invention extracts and eliminates intermediate materials between the laser material and cooling source. By using direct liquid-to-material contact without solid intermediaries, the system removes the thermal resistance and heat accumulation that occur in solid heat sinks, maintaining lower temperatures
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 approach enhances heat transfer efficiency, reduces material deformations, and increases the average power handling capacity of high-energy laser systems by eliminating film boiling and maintaining the laser material below its boiling point.
Implementation Method 1
places the amplifier in direct contact with a cryogenically-cooled flowing liquid
Implementation Method 2
a flowing cryogenically-cooled liquid... using a heat exchanger and pump to maintain efficient heat transfer
Implementation Method 3
a heat exchanger for cooling a cryogenic liquid to a chosen temperature below its boiling point
Implementation Method 4
a chamber capable of being evacuated to a chosen vacuum... for preventing condensation on the amplifier
Data Source
AI summary
A cryogenic cooling apparatus for high average power laser oscillator or amplifier, wherein the oscillator or amplifier material is in direct contact with a flowing cryogenic liquid cooled to below its boiling point is described. This method of cooling overcomes the limit in heat flux due to the onset of film boiling, thereby allowing for increased laser average power.