Nuclear Magnetic Resonance (NMR)

[EMJunkie]

Sorry for the delay in replying but I have been busy dealing with family matters.  Going back to your data posted in reply 510 where you observed a resonance at 5.695MHz.  I misunderstood the set up so my reply 512 where I thought this would be a problem was wrong.  Your reply 518 showed the set up and (if we ignore the small phase delays along the coax cables) you had the pancake coils connected in parallel having an inductance that you quoted earlier as 4.9uH at the 16mm separation, and the signal was fed from transmitter to receiver through this inductance.  The coax connections added lumped capacitance across each coil, and you also had earlier measurements of intra-turn capacitance of 174.75pF for a single pancake coil, which is far greater than the coax capacitance.   Thus you had the signal being fed through a parallel LC circuit that calculates to have a resonance of 3.85MHz based on those values, whereas the actual resonance was that 5.695MHz.  That created the dip in transmission.  That is a good result since in the actual NMR experiment we want to use resonance to get maximum current into the coils, and we can easily lower the self resonance by adding capacitance.  The bad news is that we cannot use the input matching circuit I originally proposed, which puts a high value capacitance in series with the one producing the resonance.

Now answering your specific questions, your method of connecting the coils via the S21 fixture and the Tee is simply connecting the parallel LC circuit across the 50 Ohm signal source.  This is of course a complete mismatch at resonance and does not make use of the high Q that can be obtained with better matching.  So I would expect the signal induced into the H-field sensor to follow a low Q resonance peaking at 5.9MHz.  For the phase plot I would expect this be +90 degrees at the lowest frequency, falling as the frequency rises then rising again to pass through +90 degrees at that self resonant frequency, then rising towards +180 degrees.

To maximize the current into the coils we must use a high impedance source, and that requires a step-up transformer between the 50 ohm signal source and the coils.  I am sorry that this wasn't made clear at the start, but I did not envisage the complex interleaved winding arrangements that would create such huge self capacitance.

Smudge

Aww, that's a shame, it appears there is a lot of problems in the NMR Experiment.

I hope the guys can get the problems sorted soon! Its great to see such a wonderful bunch of people working on this! Lets get to the bottom of this and see whats really achievable from the best minds on the planet! I hope, soon we can see some real progress!

Best wishes, stay safe and well in these dire times,
   Chris

[ramset]

https://www.overunityresearch.com/index.php?topic=3924.msg83849;topicseen#msg83849
Hoping things go better for you and family Cyril
Will keep your wife  in our thoughts for speedy recovery.



Thanks for all you do,
I apologize for continuing Taunts above! ( most likely he would not allow this behavior
For an instant At his forum!


With gratitude


Chet

[EMJunkie]

Wishing for a speedy and full recovery also!

No "taunt" was intended! Well wishing was!

Best wishes,
   Chris

[ramset]

All is well

And the path continues


https://www.overunityresearch.com/index.php?topic=3924.msg83987;topicseen#msg83987

[ramset]

more experiments and investigation
https://www.overunityresearch.com/index.php?topic=3924.msg84121;topicseen#msg84121