Cryostat Cold Head Mounting for Reduced NMR Vibration Coupling

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Solution Overview

Problem

Nuclear magnetic resonance (NMR) apparatuses face disturbances from mechanical vibrations introduced by the cold head in cryostats, particularly due to unilaterally pressurized bellows causing non-negligible mechanical coupling, which affects the maintenance of cryogenic temperatures and efficiency in cooling superconducting magnet coils.

Innovation Solution

A cooling device with a cold head mounted via decoupling elements to the vacuum container wall, utilizing a flexible sealing section that compensates for gas pressure differences between the cryocontainer and the environment, minimizing mechanical tension and allowing the flexible sealing section to vibrate freely, thus reducing vibration transfer to the cryostat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If unilaterally pressurized bellows are used to seal the vacuum chamber and inner chamber, then sealing effectiveness is improved, but mechanical coupling between the cold head and chambers increases causing vibrations

Engineering Contradiction:

Improvesealing effectivenessVSAvoidmechanical coupling and vibrations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary pressure compensation chamber between the cold head and the vacuum/inner chambers. This chamber acts as a mediator that equalizes pressure on both sides of the bellows, eliminating the unilateral pressure that causes mechanical coupling while maintaining the sealing function. The bellows remains pressurized for sealing but without the net unbalanced force that transmits vibrations to the cold head.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the cold head is rigidly mounted to the vacuum container wall, then structural stability is improved, but vibration transfer to the cryostat increases

Engineering Contradiction:

Improvestructural stabilityVSAvoidvibration transfer

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent applies vibration damping elements at the mounting interface between the cold head and the vacuum container wall. These elements provide beforehand cushioning that absorbs and attenuates vibrations before they can be transmitted to the cryostat structure. The mounting remains stable and secure while the damping elements prevent vibration transfer.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the flexible sealing section is subjected to large pressure differences, then sealing capability is improved, but mechanical tension increases causing vibration coupling

Engineering Contradiction:

Improvesealing capabilityVSAvoidmechanical tension

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent uses the pressure compensation chamber to apply a counterbalancing pressure effect on the flexible sealing section. By equalizing the pressure on both sides of the bellows through the compensation chamber, the net mechanical tension is reduced while the sealing capability is maintained through the controlled pressure differential.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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 configuration significantly reduces mechanical coupling between the cold head and the cryostat, minimizing disturbances during NMR measurements and maintaining stable cryogenic temperatures with reduced vibration interference.

Implementation Method 1

the flexible sealing section compensates for gas pressure differences between the cryocontainer and the environment, minimizing mechanical tension

Methodology Applied

Scientific EffectGas pressure compensation: Pressure Gradient

Implementation Method 2

the room temperature part of the cold head is mounted in a vibration-damped fashion to the vacuum container wall by means of decoupling elements

Methodology Applied

Scientific EffectVibration damping: Damping

Data Source

PatentUS9982840B2Cooling device with cryostat and cold head having reduced mechanical coupling

Publication Date: 2018.05.29 BRUKER BIOSPIN MRI GMBH

AI summary

A cooling device (20) has a cryostat (23) and a cold head (1), in particular, the cold head (1) of a pulse tube cooler. The cryostat (23) has a vacuum container (4) with a vacuum container wall (4a), wherein the vacuum container wall (4a) seals off a vacuum inside the vacuum container (4) from the environment. A flexible sealing section (6) connects the vacuum container wall (4a) directly or indirectly to the room temperature part (1a) of the cold head (1). The flexible sealing section (6) seals off the inside of the cryocontainer (2) from the environment. The cooling device further reduces mechanical coupling between the cold head and the cryostat, in particular, in order to enable performance of NMR measurements with fewer disturbances due to external vibrations.