NMR magnet system with Stirling cooler

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Solution Overview

Problem

NMR magnet systems face high operational costs and sensitivity to mechanical vibrations due to the use of two-stage pulse tube refrigerators, which require frequent servicing and induce vibrations that distort NMR signals.

Innovation Solution

A Stirling cooler is used for cold shield cooling, operating above 10 Hz to minimize vibration impact, with a flexible thermal coupling and optional damper to reduce mechanical vibrations, and a compensation apparatus to correct signal distortions caused by cooler operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If two-stage pulse tube refrigerators are used for cold shield cooling, then cooling power is provided, but mechanical vibrations are induced that distort NMR signals

Engineering Contradiction:

Improvecold shield temperatureVSAvoidmechanical vibrations

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

A vibration isolation platform is introduced as an intermediary between the PTR and the NMR magnet system. This platform mechanically decouples the vibration source from the sensitive measurement apparatus, allowing the PTR to provide cooling power while preventing vibration transmission to the magnet system.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful vibration component is extracted and isolated from the cooling system. By placing the PTR on a separate vibration isolation platform, the vibration source is separated from the NMR magnet system, allowing the beneficial cooling function to be retained while the harmful vibration is contained and reduced.

Inventive Principle:

Principle #2Taking out (Extraction)

2Temperature

If PTRs operate at low frequency (1-2 Hz), then cooling is provided, but vibrations occur at frequencies that highly impact NMR measurements

Engineering Contradiction:

Improvecold shield temperatureVSAvoidNMR signal accuracy

Core Design Contradiction:

TemperatureVSMeasurement precision

Solution Approach 1:

The operating frequency parameter of the PTR is changed from the conventional 1-2 Hz range to a higher frequency range (20-100 Hz). This parameter change shifts the vibration frequencies away from the most sensitive NMR measurement range, thereby reducing the impact on measurement precision while maintaining cooling effectiveness.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If PTRs are used for cooling, then cooling power is achieved, but high electrical power consumption and high operational costs occur

Engineering Contradiction:

Improvecold shield temperatureVSAvoidelectrical power consumption

Core Design Contradiction:

TemperatureVSUse of energy by stationary object

Solution Approach 1:

The electrical compressor system of the PTR is replaced with a mechanically-driven system. A motor-driven compressor provides the necessary high pressure for the PTR operation, replacing the electrically-driven compressor. This substitution reduces electrical power consumption and operational costs while maintaining the cooling function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The Stirling cooler reduces the need for frequent servicing, minimizes vibration-induced noise, and improves NMR measurement accuracy by compensating for mechanical vibrations and frequency distortions.

Implementation Method 1

Stirling coolers comprise a motor driving an internal compressor along a compressor axis, and a displacer that moves along a displacer axis asynchronously with respect to the compressor

Methodology Applied

Scientific EffectStirling cycle: Stirling Cycle

Implementation Method 2

The cold head is thermally connected to the cold shield via a thermal coupling

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

The Stirling cooler may be mounted on the NMR magnet system with a damper that further reduces the transmission of mechanical vibrations from the Stirling cooler to the NMR magnet system

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentUS11630172B2NMR magnet system with Stirling cooler

Publication Date: 2023.04.18 BRUKER BIOSPIN CORP

AI summary

An NMR magnet system uses a Stirling cooler having a cold head that extends into a housing of the system to cool a cold shield surrounding a cryogen vessel. The system may have a damper located between the cooler and the cold shield to reduce a transmission of vibration from the cooler to a magnet coil immersed in the cryogen. The damper may be passive, or may be part of an active damping system that uses an acceleration sensor to drive an active damper that compensates for cooler vibration. A compensation apparatus may use a stored characteristic of a signal distortion caused by the vibration and, in response to a trigger signal from the cooler, apply compensation to an excitation signal provided to a sample by an NMR probe in a bore of the magnet coil, or to an FID signal from the sample that is detected by the probe.