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OverUnity Research > Benches > Itsu (Moderator: Itsu) > Smudge proposed NMR experiment replication.
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Author Topic: Smudge proposed NMR experiment replication.  (Read 126983 times)
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Smudge proposed NMR experiment replication. « on: 2020-06-18, 10:59:43 »

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Opening this thread to discuse and replicate an NMR experiment proposed by Smudge.

It was presented 2 times already first on OUR.com, then on OU.com but quickly faded into nothingness.

First thread (2016) was here: https://www.overunityresearch.com/index.php?topic=3322.msg56207#msg56207
Second thread (2020) here: https://overunity.com/18502/nuclear-magnetic-resonance-nmr/msg546019/#msg546019

Some key PDF's presented in those threads are attached below, the important build one on top.

Also in those earlier threads good info is to be found in the form of pictures and links.

Conradelectro was so generous to 3D-print the tubular thingy to hold the water and send it to me.
I am in the process of collecting / building the rest of the setup to start experimenting.

As soon as i have something presentable i will show it here.

Be welcom to put in your comments, suggestions and replication attempts.


Regards Itsu.
   
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Re: Smudge proposed NMR experiment replication. « Reply #1 on: 2020-06-18, 11:16:56 »

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First question i had was about the below pancake coil, see red circle.
It shows 11 turns of 1mm wire, which means it will be 11mm wide.

So the shown 30mm won't cut it, but Smudge confirmed it can be 30 turns, so filling up the 30mm.

Next question i have is on the 100 turns of 1mm on the toroidal coil, which will leave 1.76mm between turns.
88mm diameter = 276mm circumference / 100 = 2.76mm.

Is this interspace needed (capacitance?) or can it be closely wound (like 276 turns)?


Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #2 on: 2020-06-18, 16:57:33 »

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Hi Itsu,
The field in the water must be as uniform as possible, so the turns need to touch each other, no gaps.  In my paper the conceived design was given more for showing the calculations, not the full details.  Thanks for sorting this out and for trying the experiment.  Thanks also to Conrad for printing the special tube.
Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #3 on: 2020-06-18, 17:02:41 »

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Thanks Smudge,  your welcom.

How about the pancake coils connection, in series OK, but bucking or aiding?

This means i need to make the both pancake coils similar (bucking) or mirror like (aiding).

Thanks,  Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #4 on: 2020-06-19, 16:05:58 »

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Hi Itsu,

To get the wanted radial field between the pancake coils they have to be connected in series opposing.  That is the driving field.  The toroidal coil is the output coil.  I was wrong in my previous post where I talked about getting the field from the toroidal coil as uniform as possible, that was perhaps misleading.  It is the static field from the magnet that has to be as uniform as possible throughout the water volume.  That requires the geometry to be carefully made as symmetrical as possible.  Unfortunately you won't have control of the magnetization in the magnets, so it may be necessary to create some form of adjustment to minimise any assymmetry of that magnetization.  The static field in the water is the one that the protons precess about, and their precession frequency is determined by the field magnitude.  Ideally we want uniform static field so that all the protons precess at precisely the same frequency, that would give infinite Q.  It would require zero energy to get all the protons to precess in phase.  But that can't happen, there will be a spread of precession frequencies hence they will never under normal circumstances be in phase, the spread of random phases results in a zero RF output.  The smaller the spread of frequencies the easier it is for the RF drive to create some phase coherence.  Then the precessing protons act like an array of tiny precessing bar magnets, driven by some inner quantum forces to be persistently precessing.  Extracting power via the toroidal coil will try to slow those precessions down, so the field from load current in that coil does need to be uniform so as not to create varying slowing down rates that will inevitably reduce the phase coherence.

Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #5 on: 2020-06-19, 16:39:54 »

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Thanks Smudge, 

so opposing (bucking) series it is for the pancake coils.

I have the both ring magnets, they are huge.

Still waiting for the special tube from Conrad, so i can concentrate on building the pancake coils for now.


Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #6 on: 2020-06-19, 16:53:31 »
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I am glad that Itsu will try the experiment. His electronics expertise is much higher than mine.

I sent the circular tube last Friday (12th June), but the Austrian postal services have a backlog of 100.000 packages because of coronavirus outbreaks in two distribution centres near Vienna. So, it might take an other week till Itsu gets the tube. Which he then has to cover with an epoxy glue, because the tube is not completely watertight.

If Itsu needs more or different tubes I am ready to print and send them.

Greetings, Conrad
   
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Re: Smudge proposed NMR experiment replication. « Reply #7 on: 2020-06-20, 10:54:46 »

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Thanks Conrad.

I received the tube today, see picture 1

Up till now i have the tube, the molds for the pancake coils and the ring magnets, see picture 2

Will be needed to seal the tube first, and start winding the pancake coils etc.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #8 on: 2020-06-20, 12:21:53 »
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Quote from: Itsu on 2020-06-20, 10:54:46
I received the tube today, see picture 1

Up till now i have the tube, the molds for the pancake coils and the ring magnets, see picture 2

Will be needed to seal the tube first, and start winding the pancake coils etc.

Within the EU, I am willing to send a tube to experimenters. Outside the EU I will send the .stl file by E-Mail and one can have it 3D-printed locally (which is cheaper than sending by mail, there are enterprises everywhere who do the 3D-printing for a good price or you find someone who has a 3D-printer, private individuals, clubs or schools).

I also design tubes with other dimensions if needed.

Once Itsu has done first tests the requirements (specially for the electronics) will be clearer.

Amplification of the ~4 MHz drive sinus signal (from a function generator) for the input pancake coils and preamplification of the output signal (from the toroidal coil around the tube) for the scope are the issues to be solved. And Itsu has this covered.

I like the big ring magnets, are they strong enough to hurt fingers if handled carelessly?

Greetings, Conrad
   
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Re: Smudge proposed NMR experiment replication. « Reply #9 on: 2020-06-20, 13:11:18 »

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Quote from: Smudge on 2020-06-18, 16:57:33
It seems all NMR experiments looking for OU use ferromagnetic material, presumably on the basis that such material will yield the largest magnetic output.
This inevitably creates problems with uniformity of the static magnetic bias because of the shape dependent depolarising field.
No, these experiments target the 33 Tesla internal hyperfine fields of the ferromagnetic domains.  They are very different from the water-tube experiment, which Itsu is performing in this thread.
The magnitudes of these huge internal hyperfine fields are inherently uniform because any external fields are so small compared to them (...and anti-parallel)

See the attached paper.
« Last Edit: 2020-06-20, 13:36:41 by verpies »
   
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Re: Smudge proposed NMR experiment replication. « Reply #10 on: 2020-06-20, 13:36:20 »

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Quote from: Smudge on 2020-06-19, 16:05:58
It is the static field from the magnet that has to be as uniform as possible throughout the water volume.  That requires the geometry to be carefully made as symmetrical as possible.  Unfortunately you won't have control of the magnetization in the magnets, so it may be necessary to create some form of adjustment to minimize any asymmetry of that magnetization.
Yes, this uniformity is of paramount importance, so some kind of mechanical screw adjustment of the magnets' planes should be implemented in two perpendicular axes.

Quote from: Itsu on 2020-06-19, 16:39:54
Still waiting for the special tube from Conrad, so i can concentrate on building the pancake coils for now.
The pancake coils are the drive coils.  I am very interested what inductance they will have because this inductance presents an inductive reactance to the driving signal ...and limits the AC current in the these coils.
In other words, the smaller the inductance of these pancake coils - the easier it is to push AC current into them.

The input LC tank will help a lot with maintaining the amplitude of this driving current BUT this LC circuit is frequency selective ! 
This selectivity complicates the entire endeavour because it takes away the freedom of an easy adjustment of the driving frequency by the means of merely turning a knob on Itsu's signal generator. (He will need to: Turn the knob & Adjust the LC tank, Turn the knob & Adjust the LC tank, Turn the knob & Adjust the LC tank...)
And this driving frequency will need to be adjusted frequently in order to match the Larmor frequency, which changes as the magnets are adjusted for the best uniformity of the magnetic field density - which is a crucial factor in any NMR.

Also, while Smudge is correct in theory that "we can easily decouple the output from the input by the use of coils at right angles", the parallel orientation of the drive coils to the magnets, the I/O capacitive coupling and the sheer proximity of the pancake drive coils to the toroidal output coil will make it impossible in practice (they will couple even acoustically!).
Also, the nulling out of this crosstalk by "either by careful layout taking account of the “hot” end of the drive or by adding extra trimmer" is practically impossible according to my experiences.

So in my opinion, the only way Itsu will be able to observe the NMR signal with this setup will be to turn off the driving signal and listen for the decaying Larmor precession (FID).
In other words: TDM.
« Last Edit: 2020-06-20, 16:15:52 by verpies »
   
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Re: Smudge proposed NMR experiment replication. « Reply #11 on: 2020-06-20, 16:15:40 »

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@Itsu

Notice that the flux generated by the pancake coils becomes perpendicular to the PM's flux (green vertical arrow) somewhere outside of the OD of these coils (inside gray circles), so you should make these pancake coils smaller than the mean diameter of your sample (water) holder ring.
A quick experiment with a miniature compass will show you the angle of that field when DC is flowing through the pancake coils (in absence of the magnets).
   
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Re: Smudge proposed NMR experiment replication. « Reply #12 on: 2020-06-20, 16:50:58 »

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thanks verpies,

all valid points i am sure and a good time to mention them as now i still have the time and possibility to implement any hardware / electronic changes.

For the tuning a PLL system comes in mind.

Also the mentioned TDM (Time-division multiplexing) still is on the back of my mind in case needed.


Concerning the pancake coil diamater, "the mean diameter of your sample (water)" is 100mm, while the pancake coils cover 70 to 130mm diameter, so do you mean the pancakes should be like 40 to 100mm or so?

Lets see how easy(or not) it is to produce the 70 to 130mm pancakes, then i can always deviate from it.


Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #13 on: 2020-06-20, 17:10:30 »

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Quote from: Itsu on 2020-06-20, 16:50:58
For the tuning a PLL system comes in mind.
Our PLL system adjusts the driving frequency to automatically match the resonance frequency of an LC tank.
This NMR system with the LC circuit at the input, needs to change BOTH frequencies !
   
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Re: Smudge proposed NMR experiment replication. « Reply #14 on: 2020-06-20, 17:40:42 »

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Quote from: Itsu on 2020-06-20, 16:50:58
Concerning the pancake coil diamater, "the mean diameter of your sample (water)" is 100mm, while the pancake coils cover 70 to 130mm diameter, so do you mean the pancakes should be like 40 to 100mm or so?
Yes. just power them up with DC and stick a small compass in the plane between them, to see their field angles.

Also, pancake coils that "cover 70 to 130mm diameter" must have many turns...and consequently a large inductance (even when connected in series). 
Consider how much RF current you will be able to push into coils of such large inductive reactance ?
...and how small the capacitor needs to be to resonate with the pancake coils at the Larmor frequency (and will the intrawinding capacitance be larger than that ) ?
   
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Re: Smudge proposed NMR experiment replication. « Reply #15 on: 2020-06-20, 18:14:53 »

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Quote
Our PLL system adjusts the driving frequency to automatically match the resonance frequency of an LC tank.
This NMR system with the LC circuit at the input, needs to change BOTH frequencies !

Yes, during my diner just now that dawned on me.


Quote
Yes. just power them up with DC and stick a small compass in the plane between them, to see their field angles.

Also, pancake coils that "cover 70 to 130mm diameter" must have many turns...and consequently a large inductance (even when connected in series).
Consider how much RF current you will be able to push into coils of such large inductive reactance ?
...and how small the capacitor needs to be to resonate with the pancake coils at the Larmor frequency (and will the intrawinding capacitance be larger than that ) ?


In my 2th post above you see the initial pancake coil turns were 11, but it showed a 30mm area, so we now changed that to 30 turns.

I will make one and do the compass test, measure the inductance and we go from what we find.

Itsu

 
   
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Re: Smudge proposed NMR experiment replication. « Reply #16 on: 2020-06-21, 08:04:16 »

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Quote from: verpies on 2020-06-20, 16:15:40
@Itsu

Notice that the flux generated by the pancake coils becomes perpendicular to the PM's flux (green vertical arrow) somewhere outside of the OD of these coils (inside gray circles), so you should make these pancake coils smaller than the mean diameter of your sample (water) holder ring.
A quick experiment with a miniature compass will show you the angle of that field when DC is flowing through the pancake coils (in absence of the magnets).
Verpies,

Sorry, but that image is misleading as it doesn't show pancake coils.  For the NMR it is the flux flowing over the surface.of the pancake which is radial to the axis of the water ring.  It is that flux which is then perpendicular to the magnet flux in the water..  What you show are two non-pancake current rings which of course require a special geometry to get their flux to meet this requirement of perpendicular fluxes in the water.  I agree with your concerns for getting the needed RF
current in the pancake coils.

Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #17 on: 2020-06-21, 09:15:43 »

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Here is an FEMM result to show the flux between the pancake coils.  The outer blue circle is simply the boundary for the FEMM simulation.  The pancake coils are modeled as current strips with the current going into or out of the screen, which is a reasonable representation for a single layer of closely spaced wires.  Of course FEMM is only a 2D simulation so it is showing the results for current strips that are infinitely long: it will not give an accurate figure for the actual flux from coils, but it does give a picture of what the flux looks like.

With regard to the problem of searching for the NMR effect, having to adjust both the tuning of the pancake coils and the drive frequency together, I would hope that we can make a good stab at the field from the magnets.  If we know that accurately then we also accurately know the NMR frequency, so the search window is not very wide.

Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #18 on: 2020-06-21, 17:39:52 »

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Quote from: Smudge on 2020-06-21, 08:04:16
Sorry, but that image is misleading as it doesn't show pancake coils.
...
Here is an FEMM result to show the flux between the pancake coils. 
The micro compass measurement will demonstrate that empirically
   
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Re: Smudge proposed NMR experiment replication. « Reply #19 on: 2020-06-21, 20:07:44 »

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First pancake coil is drying, it measures 115uH @ 100Khz.

Inner diameter is 7cm,  outer diameter 13cm, 30 turns of 1mm wire

Micro compass on its way.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #20 on: 2020-06-22, 09:48:19 »

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So if you apply a 100V RMS, 4MHz sine tone to this coil, then 35mA RMS current will flow through it, because at this frequency its inductive reactance is 2890Ω

The capacitance needed to make a 115µH inductance resonate at 4MHz is 14pF. An impractical value because this coil also has some intrawinding capacitance, which is hard to measure.  It can be calculated from its self-resonance frequency which can be determined experimentally with an FM sweep (which you've done many times before).

Also, when two pancake coils are connected and sandwiched, their inductance will change due to their connection and mutual inductance.
« Last Edit: 2020-06-22, 10:33:29 by verpies »
   
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Re: Smudge proposed NMR experiment replication. « Reply #21 on: 2020-06-22, 10:31:33 »

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OK, 14pF is indeed somewhat impractical as probably the intrawinding capacitance will be similar.

When the coil is dry, i will try to establish its intrawinding capacitance.

It could be we have to go back in number of turns (30) to the original 11 or so.

Itsu
   
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Re: Smudge proposed NMR experiment replication. « Reply #22 on: 2020-06-22, 11:04:39 »
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Here I show the calculation of self resonance and self capacitance of a pancake coil (note the description of the video), but Itsu knows that anyway.

https://www.youtube.com/watch?v=spQ9yLdb7v4

Small capacitors (like 14 pF) can be easily built and they are even variable:

Variant 1: Cut two pieces from a metal sheet (aluminium, copper, steel) about 5 cm x 10 cm. Put a plastic foil in between and let the two metal sheets overlap more or less to adjust capacitance. Use bigger or smaller metal sheets to adjust maximum capacitance.

Variant 2: Cut two lengths of insulated wire (10 cm or 20 cm) and twist the two wires for a shorter or longer length to adjust capacitance, see screenshot of a 1 pF twisted wire cap.

https://www.youtube.com/watch?v=v1wWL6TGWOE This person makes a 6 pF cap at the end of the video.

Greetings, Conrad
« Last Edit: 2020-06-22, 15:40:41 by conradelektro »
   
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Re: Smudge proposed NMR experiment replication. « Reply #23 on: 2020-06-22, 16:16:22 »

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Don't forget that the two pancake coils are connected in series opposing, and they are relatively close to each other.  In FEMM I get 100uH for one coil and 67uH for the two coils in series opposing.  So that 100:67 is the ratio you can expect.

Smudge
   
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Re: Smudge proposed NMR experiment replication. « Reply #24 on: 2020-06-22, 17:23:58 »

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Thanks Conrad,   thanks Smudge.


I did some measurements on the pancake coil, like the FM sweep (1Khz - 10Mhz), see screenshot 1 and a square wave ping and capture the damped oscillations, see screenshot 2.

Both show a resonance point of the pancake coil (30t) to be around 4.58Mhz or so.

Probe used was 3.9pF / 10MOhm.

Itsu
   
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