Quote:
Originally Posted by humhum
Borrowing:
Gold has an NMR frequency of 1.754MHz relative to hydrogen @ 100MHz, which establishes the test magnetic field at about 2.35T. The Earth has an average field of about 50uT, so buried gold would have an NMR frequency of about 37Hz. Someone please correct me if I'm wrong.
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Hi,
well maybe calculation is good... I didn't check it... but NMR data collecting is possible when the target is inside the coil... not outside...
The problem is that even a big gold target will generate so small decaying Larmor compliant precession signal that you will not be able to "read" with a coil from far away few distance.
You need a static magnetic field (in your idea it's the Earth's magnetic field you said) and a perturbing magnetic field orthogonal to the first.
You need them PERFECTLY orthogonal, you need to apply well known field intensity to align particles (nuclei having a magnetic moment if you really want do NMR) and then shut down and let them precess at required frequency.
Then you read the signal by a e.g. an rx coil... or just measure e.g. absorbtion of energy at this particular frequency (nmr related loss).
A thing you must consider is the energy required to do so with macroscopic objects is really enormous and you will probably need some 1-10 tesla induction system (using superconductors and "small" portable power source I think... for portable unit
.... say you need maybe from 10KW to 1MW power depending on conditions...
just to supply the coil... then a dynamic platform that will align coil orthogonal to soil... uhm seems science fiction now....?
)
Seems not an easy project... so good luck!
Kind regards,
Max