Bolted joint conduction cooling apparatus for accelerator cavities
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Solution Overview
Problem
Conventional conduction cooling methods for accelerator cavities face issues with thermal contact resistance due to loosening of bolted joints caused by differential thermal contraction, leading to prolonged cooldown times and performance degradation from magnetic interference by pressure retention devices.
Innovation Solution
A conduction cooling system using niobium cooling rings and copper conduction links with connection assemblies made of materials experiencing greater thermal contraction, eliminating the need for pressure retention devices and reducing oxidation, coupled with a thermal switch that adjusts conductance based on temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum links are used for conduction cooling, then thermal conductivity is improved, but thermal contact resistance increases due to loosening of bolted joints from differential thermal contraction
Solution Approach 1:
The patent applies thermal expansion principle by selecting connection assembly materials (brass or bronze) that experience greater thermal contraction than the niobium cooling ring when cooled from room temperature to 4 Kelvin. This differential thermal contraction ensures the bolted joint maintains or increases mechanical pressure rather than loosening, thereby maintaining low thermal contact resistance throughout the cooling process.
Solution Approach 2:
The patent changes the material parameter of the connection assembly from steel (in disc springs) to brass or bronze, which have different thermal contraction characteristics. This parameter change allows the joint to maintain proper mechanical pressure during thermal cycling without introducing magnetic interference, resolving the contradiction between cooling efficiency and thermal contact resistance.
2Reliability
If pressure retention devices such as disc springs are used, then mechanical pressure at joints is maintained, but magnetic fields are introduced causing performance degradation
Solution Approach 1:
The patent changes the material composition of the connection assembly from steel (ferromagnetic) to brass or bronze (non-magnetic). This parameter change eliminates magnetic interference while maintaining the ability to retain mechanical pressure through controlled thermal contraction, thus resolving the contradiction between pressure maintenance and magnetic interference.
Solution Approach 2:
The patent extracts the pressure retention function from separate steel disc springs and integrates it into the connection assembly materials themselves (brass or bronze bolts and nuts). This extraction eliminates the need for separate magnetic materials while maintaining the pressure retention function through material selection based on thermal contraction properties.
3Temperature
If aluminum components are used, then thermal conductivity is improved, but thermal contact resistance increases due to oxide layer formation
Solution Approach 1:
The patent uses composite material strategy by combining aluminum (for high thermal conductivity) with indium (for low oxidation and high thermal contact). The indium layer is applied to aluminum surfaces to prevent oxide formation, creating a composite structure that maintains both high thermal conductivity and low thermal contact resistance at interfaces.
4Temperature
If conventional conduction cooling systems are used, then cooling capability is achieved, but cooldown time is prolonged to multiple days
Solution Approach 1:
The patent applies thermal expansion principle to maximize thermal contact at all temperatures by selecting materials with appropriate differential contraction rates. The connection assembly materials (brass or bronze) are specifically chosen to contract more than niobium when cooled, ensuring continuous intimate contact between mating surfaces throughout the cooldown process, which maximizes thermal conductance and reduces cooldown time.
Solution Approach 2:
The patent implements self-service by designing the connection assembly to automatically maintain or increase mechanical pressure through its own thermal contraction during cooldown. The brass or bronze materials self-adjust to maintain optimal contact pressure without requiring external adjustment mechanisms, ensuring consistent thermal performance throughout the temperature range and reducing cooldown time.
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
Enhances thermal conductivity, maintains mechanical pressure at joints, reduces cooldown time, and minimizes magnetic interference, resulting in efficient and rapid cooling of accelerator cavities.
Implementation Method 1
selecting the materials in the at least one connection assembly to experience greater thermal contraction than the cooling ring and the conduction link when cooled
Implementation Method 2
a thermal switch that adjusts conductance based on temperature
Implementation Method 3
conduction cooling system comprises at least one cooling ring connected to a cavity, configuring a conduction link to be joined to the cooling ring
Data Source
AI summary
Methods and systems for bolted joint conduction cooling of accelerator cavities comprises a conduction cooling system. The conduction cooling system comprises mounting at least one cooling ring to a cavity and a conduction link joined to the cooling ring with at least one connection assembly. The materials in the at least one connection assembly can be selected to experience greater thermal contraction than the cooling ring and the conduction link when cooled. A fast conduction cooling system can comprise a cryocooler in thermal communication with a conduction cooling apparatus affixed to a cavity via a conduction path and a thermal switch in the conduction path between the cryocooler and the conduction cooling apparatus wherein a thermal conductance of the thermal switch decreases as a function of temperature.