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Flux stabilization insert
Flux sensor inside 5 mm liquids probe |
1. PURPOSE
We are developing a 25 Tesla, 52 mm
Bitter resistive magnet (also known as Keck Foundation magnet) for NMR applications. Field instability is the most significant disadvantage
of resistive magnets when compared to permanent and superconducting magnets.
This clear-bore device is inserted from top of the magnet to correct such field instability.
A separate flux sensor coil is installed inside NMR probe around RF coil to pick up changes in magnetic flux.
By using miniaturized version of sensor coil one can focus on field fluctuations happening directly in the area of NMR sample.
The signal obtained from sensor coil is used to drive insert’s own correction coil, which, in turn, cancels field fluctuations.
The clear bore of insert is large enough to allow industry standard 40 mm NMR probes, which are inserted from below.
A custom sample loader has been designed for quick NMR sample tube replacement
without disturbing probe setup and re-tuning, which is essential because of considarable hourly cost of electricity in resistive cells.
2. DIMENSIONS
Clear bore ID = 41 mm
Top flange to center of field distance = 559 mm
Interchangeable correction coil sections
3. EXAMPLE
Shown below is spin-echo phase histogram with flux stabilizer on and off.
Time between 90 degree pulse and appearance of an echo is 2 ms.
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