Thermal Mass Vacuum Maintenance for Superconducting Magnets
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Solution Overview
Problem
Superconducting magnet systems face challenges in maintaining a vacuum when the cryogenic cooling environment is lost, leading to rapid warming and potential release of stray molecules captured by getters, requiring costly and time-consuming vacuum pump-downs.
Innovation Solution
A system comprising a getter material within a vacuum chamber, a thermal mass in thermal communication with the getter, and a convective cooling loop that isolates the thermal mass from the cold station when it's warmer, maintaining the vacuum by cooling the getter material and thermally isolating it from the cold station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small amount of liquid helium is used in a sealed system to cool the superconducting magnet, then the system complexity is reduced, but the thermal heat capacity at low temperatures becomes insufficient, causing rapid warming above 20°K when cooling is lost
Solution Approach 1:
The patent introduces a thermal mass component that is pre-cooled to cryogenic temperatures before normal operation. This thermal mass acts as a preliminary thermal reservoir that can absorb heat influx when the cryocooler fails, delaying the temperature rise of the getter material and maintaining vacuum conditions for an extended period without requiring complex active cooling systems.
Solution Approach 2:
The thermal mass serves as an intermediary thermal buffer between the cold station and the getter material. It absorbs thermal energy from the getter when cooling is lost, mediating the thermal interaction and preventing direct heat transfer that would cause rapid warming. This intermediary approach resolves the contradiction by adding thermal inertia without significantly increasing system complexity.
2Temperature
If the getter is allowed to heat up during loss of cooling, then the thermal mass provides thermal buffer, but the stray molecules captured by the getter are released into the vacuum chamber, requiring expensive and time-consuming vacuum pump down
Solution Approach 1:
The patent positions the thermal mass in thermal communication with the getter material to provide beforehand cushioning against temperature rise. When cooling is lost, the thermal mass absorbs heat that would otherwise immediately warm the getter and release captured molecules. This prior thermal cushioning maintains vacuum reliability by keeping the getter temperature below the threshold for molecular release.
Solution Approach 2:
The patent converts the potential harm of thermal mass heating into a benefit by using the thermal mass as a heat sink that protects the getter. The thermal mass willingly absorbs thermal energy that would be harmful to the getter, transforming the harmful heat influx into a beneficial thermal buffering effect that maintains vacuum conditions.
3Reliability
If a convective cooling loop is used to cool the thermal mass, then the getter material can be maintained at low temperature to absorb stray molecules, but the system complexity increases with additional cooling infrastructure
Solution Approach 1:
The patent implements a passive convective cooling system where the cooling loop relies on natural convection currents driven by temperature differences between the cold station and thermal mass. The system self-regulates without requiring active pumps or complex control mechanisms - when the cold station is colder than the thermal mass, convective current automatically flows to cool the thermal mass, maintaining vacuum reliability through self-service cooling.
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 extends the time the vacuum can be maintained, preventing the release of stray molecules and reducing the need for frequent pump-downs, even when the cryocooler is not operational, thus protecting the superconducting magnet system.
Implementation Method 1
a convective cooling loop connected between the thermal mass and the cold station and configured to convectively cool the thermal mass when the cold station is at a lower temperature than the thermal mass
Implementation Method 2
a first getter material disposed within a vacuum chamber and which is configured to absorb stray molecules within the vacuum chamber
Implementation Method 3
to substantially thermally isolate the thermal mass from the cold station when the cold station is at a higher temperature than the thermal mass
Data Source
AI summary
An apparatus includes: a getter material disposed within a vacuum chamber to absorb stray molecules within the vacuum chamber; a thermal mass disposed adjacent the getter material and in thermal communication with the getter material; a cold station disposed within the vacuum chamber above the thermal mass; and a convective cooling loop connected between the thermal mass and the cold station and configured to convectively cool the thermal mass when the cold station is at a lower temperature than the thermal mass, and to thermally isolate the thermal mass from the cold station when the cold station is at a higher temperature than the thermal mass. The thermal mass may be water ice and may be thermally isolated from the walls of vacuum chamber by low loss support links and/or thermal reflective shielding.