NMR Stray field shielding

NMR stray field shields are required to reduce the strong magnetic fields of NMR’s, mostly to maintain the 5 gauss line. However, the application of the shields does not have to remain on the limit of 5 gauss lines. With the shielding system Systron PowerShield® STF-I, stray fields can be reduced to other values.

Description

NMR stray field shielding system Systron PowerShield® STF-I

berechnung600mhz-kleinSimulation of the shielding effect on the computer
 
With the Systron PowerShield® STF-I stray field shielding system, stray fields of NMR’s are being shielded. The shielding system is used for both, shielded or unshielded NMR’s.
 
The surface and thickness needed for the shield is being calculated with a computer simulation. Only tested materials defined by the NMR-manufacturer are used for the shielding. These materials also match the computer characteristic values for the defined materials. 
 
The Systron PowerShield® stray field shielding STF-I is used as ground, wall or ceiling shielding. In this combination, whole rooms can be shielded.

Novartis Research Laboratory

Limiting the NMR stray fields upwards and downwards with the Systron PowerShield® stray field shielding to ensure compliance with the 5 gauss line

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NMR in the research laboratory

 
Initial situation
The stray fields of a research –NMR should be shielded upwards and downwards in order to comply with the 5 gauss line. In advance, the effect of the shielding will be checked with a test shield surface, laid on the floor of the room above the NMR.
bodenbefestigung

Fixing the shield with nail gun technology

 
Mounting of the surface shield
In order to lay the shielding without any offset, the existing underlay floor below the magnets and on the floor above is removed. The shield is then laid on a surface of 56m2.

Used as shielding is the stray field shielding Systron PowerShield® STF-I. After the laying, the shield panels are fixed on the floor with a special shot technology.

bodenabgeschirmt

Ready laid shielding before covered with liquid mortar

 
Ready-mounted floor shield
After installation, the shields are covered with a liquid mortar. The floor is then covered in a plastic coating. The shielding disappears therefore and is therefore invisible.

University of Konstanz

Fields of an NMR should be limited upwards (auditorium) to comply with the 5 gauss line.

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Initial situation
The lecture hall of the university is directly above the NMR-room. The computer simulation shows that the 5 gauss line penetrates into the auditorium. In order to comply with the limit values the stray fields in the auditorium have to be limited to max. 5 gauss.
Auditorium above NMR-room  
 
ansys-mit-abschirmungStray field plot with shielding
 
Software simulation
The surface and thickness of the necessary shielding for the limitation of the fields is determined with a finite element calculation. According to the calculation, a surface of 64m2 and thickness of 4mm is required for the shielding mounted on the ceiling of the NMR-room.
deckenabschirmung-klein
Mounting of the shielding panels
 
Mounting the shield
The shield is mounted on the 5m high ceiling with the help of a scissors lift. The individual shielding elements consist of several layers of silicon iron. The elements are mounted in several layers, therefore impact joints of the lower layers are covered with the following layer.
 
The multi-layered elements will be placed accurately with the hydraulic lifters which are installed on the scissors lift and screwed tight with special heavy duty anchors.
nmr-raum800x600
 
NMR Room
The fully furnished NMR-room below the lecture hall. The ceiling shield is installed and painted white. Ventilation installations, gas etc. are directly mounted onto the shield.

A ceiling mounting construction, which is used for the mounting of the shielding panels and installations, was chosen in close cooperation with the planners. Therefore it could be prevented, that the shield had to be pierced again.
Fully set up NMR room
 
 
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Control measurements
After the commissioning of the NMR, the effect of the shielding was measured in a 50x50cm grid on the floor of the auditorium. The field elevations >5 gauss to one side were measured in a built-in cabinet, which could not and does not need to be shielded.
 
Conclusion: The measurements agree well with the calculations. The 5 gauss line is perfectly fulfilled. The lecture hall can therefore be released.
Measured values on the ground in the auditorium
 
 
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