Superconducting Magnet Oscillation Systems for Heat Reduction

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Solution Overview

Problem

Conventional superconducting magnet configurations in magnetic resonance apparatuses experience excessive heat input due to eddy currents, leading to rapid helium evaporation and operational downtime, despite active shielding and cooling measures.

Innovation Solution

The configuration employs low temperature oscillation systems with high electrical conductivity values and warm oscillation systems with lower conductivity values, differing mechanical characteristics, to dampen eddy currents and redirect heating away from the superconducting wire, using materials like copper and nonmagnetic stainless steel, and strategically positioning these systems within the magnet coil and cryostat to minimize heat transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional superconducting magnet configurations are used with active shielding and cooling measures, then strong magnetic fields can be generated in the working volume, but excessive heat input due to eddy currents causes rapid helium evaporation and operational downtime

Engineering Contradiction:

Improvemagnetic field strengthVSAvoidhelium evaporation rate

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The oscillation system is divided into multiple sections (first oscillation system and second oscillation system) with different characteristic mechanical values, allowing each section to have optimized electrical conductivity properties for reducing eddy current heating while maintaining magnetic field generation capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the oscillation system have different electrical conductivity values - the first oscillation system has higher conductivity while the second has lower conductivity, creating local quality variations that reduce overall eddy current heating in the superconducting magnet configuration

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If electrically conducting bodies are positioned inside the magnet winding to support the structure, then mechanical stability is improved, but eddy currents in these bodies produce heat that evaporates liquid helium and may overheat the superconducting wire

Engineering Contradiction:

Improvestructural stabilityVSAvoidheat input to superconducting wire

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The electrical conductivity parameter is varied across different sections of the oscillation system, with the first section having higher conductivity and the second section having lower conductivity, thereby changing the heat generation characteristics and reducing overall thermal load on the superconducting wire

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces heating in low temperature oscillation systems, minimizing helium consumption and extending operational periods by effectively damping mechanical oscillations and eddy currents, thereby maintaining a stable magnetic field.

Implementation Method 1

The oscillating motion of an electrically conducting body in a strong magnetic field, in turn, produces eddy currents in this body

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Implementation Method 2

Switching of the gradient coil and the associated magnetic field change induce electric currents in nearby electrically conducting, in particular, metallic bodies

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

When these bodies are simultaneously exposed to a strong magnetic field, which prevails radially inside the magnet winding of the magnet coil, these electric currents produce Lorentz forces which elastically deform the bodies

Methodology Applied

Scientific EffectLorentz force: Lorentz Force

Implementation Method 4

These eddy currents produce heat due to the ohmic resistance in the body

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 5

The superconducting materials used in the magnet coil are cooled below the transition temperature such that large electric currents and magnetic field strengths can be produced by the magnet coil in this superconducting state

Methodology Applied

Scientific EffectSuperconductivity: Superconductivity

Data Source

PatentUS7514928B2Superconducting magnet configuration with reduced heat input in the low temperature regions

Publication Date: 2009.04.07 BRUKER BIOSPIN MRI GMBH

AI summary

The invention concerns a magnet configuration comprising a superconducting magnet coil (1) within which a gradient system is to be switched. All low temperature oscillation systems (R1) with a temperature T1<10K within the magnet coil (1) are produced from a material having good electrical conducting properties, and at least one warm oscillation system (R2) with a temperature T2>10K within the magnet coil (1) has worse electrical conducting properties and has a considerably different mechanical resonance frequency (separation approximately 500 Hz or more) than at least one of the low temperature oscillation systems (R1). This reduces the undesired heating power supplied to the low temperature oscillation systems due to mechanical oscillations and induced eddy currents.