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John Larkin
Guest

Fri Feb 08, 2019 10:45 pm   



On Fri, 8 Feb 2019 12:33:33 -0600, amdx <nojunk_at_knology.net> wrote:

Quote:
On 2/7/2019 8:33 AM, George Herold wrote:
Hi all, A (mostly clueless) physics type wants to do some RF stuff. (measuring nmr signals.. protons, ~5-25 MHz range) He's got something
working, but construction is ugly. I was thinking of recommending an ARRL handbook, is any version better than others?


Show him some of Larkin's dremel cut boards or this link to images of
Manhattan style circuits. Some well done prototypes there!
https://www.google.com/search?q=manhattan+style+circuit&client=firefox-b-1-d&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjn1siv4qzgAhULWa0KHRAjCKgQ_AUIDigB&biw=1440&bih=690#imgrc=_

Mikek


One of mine showed up on that page!

https://hackadaycom.files.wordpress.com/2016/05/0gfwt.jpg?w=548&h=370




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

John Larkin
Guest

Sat Feb 09, 2019 1:45 am   



On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
<gherold_at_teachspin.com> wrote:

Quote:
On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.


There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Jeff Liebermann
Guest

Sat Feb 09, 2019 1:45 am   



On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
<gherold_at_teachspin.com> wrote:

Quote:
On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.


I found the 1980, 1993, and 2003 ARRL Antenna Handbooks.

Quote:
5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.


I doubt you'll find much of that in the ARRL handbook. In about 1980,
I worked on a 200 watt CW VMOS power amplifier for some NMR
contrivance. The major specification was very good linearity so that
the IMD (intermodulation distortion) was as low as possible. Also,
reasonably flat 50 ohm output impedance to make impedance matching to
the NMR coil(s) as easy as possible. The amp worked just fine.
However, I never became involved in the system design, and never saw
the final product. Since then, I've done nothing with NMR.
Presumably, there's been some technical progress in the last 39 years.

Looking at the photos that Google Images excavates from the web:
<https://www.google.com/search?q=nmr+probe&tbm=isch>
the mechanical design of the probe coil or coils is rather
complexicated. Fortunately, single frequency probe coil matching
methods (i.e. coupling) that you're looking for is fairly well
described with a simple "L" match:
<http://www.chem.wilkes.edu/~trujillo/NMR_Course/usask_ca_PROBE_PICTURES/>
<https://www.eeweb.com/tools/l-match>
Just plug the probe coil into a network analyzer and do whatever it
takes to make S21 look like 50 ohms over the frequency range of
interest. Unfortunately, things rapidly become a mess with dual and
triple resonant probe coils. From there and beyond, I'm ignorant of
the technology and really don't know enough about the probe coil to
offer any good links or methods.

>(Sorry about your H2O situation.)

Thanks, but I'll be fine. Such things happen every 5 to 10 years. I'm
prepared with about 40 gallons of stored drinking water, which should
be sufficient for a week or more. I could run my own test, but it
takes 48 hrs to grow the bacteria in the same. I might as well wait
for the water district to make the determination.
<https://watertestingkits.com/product/bacteria-water-test/>

--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

George Herold
Guest

Sat Feb 09, 2019 2:45 am   



On Friday, February 8, 2019 at 6:54:18 PM UTC-5, Jeff Liebermann wrote:
Quote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

I found the 1980, 1993, and 2003 ARRL Antenna Handbooks.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

I doubt you'll find much of that in the ARRL handbook. In about 1980,
I worked on a 200 watt CW VMOS power amplifier for some NMR
contrivance. The major specification was very good linearity so that
the IMD (intermodulation distortion) was as low as possible. Also,
reasonably flat 50 ohm output impedance to make impedance matching to
the NMR coil(s) as easy as possible. The amp worked just fine.
However, I never became involved in the system design, and never saw
the final product. Since then, I've done nothing with NMR.
Presumably, there's been some technical progress in the last 39 years.

Looking at the photos that Google Images excavates from the web:
https://www.google.com/search?q=nmr+probe&tbm=isch
the mechanical design of the probe coil or coils is rather
complexicated. Fortunately, single frequency probe coil matching
methods (i.e. coupling) that you're looking for is fairly well
described with a simple "L" match:
http://www.chem.wilkes.edu/~trujillo/NMR_Course/usask_ca_PROBE_PICTURES/
https://www.eeweb.com/tools/l-match
Just plug the probe coil into a network analyzer and do whatever it
takes to make S21 look like 50 ohms over the frequency range of
interest. Unfortunately, things rapidly become a mess with dual and
triple resonant probe coils. From there and beyond, I'm ignorant of
the technology and really don't know enough about the probe coil to
offer any good links or methods.

(Sorry about your H2O situation.)

Thanks, but I'll be fine. Such things happen every 5 to 10 years. I'm
prepared with about 40 gallons of stored drinking water, which should
be sufficient for a week or more. I could run my own test, but it
takes 48 hrs to grow the bacteria in the same. I might as well wait
for the water district to make the determination.
https://watertestingkits.com/product/bacteria-water-test/

My water comes from my well right outside the back door.
Except for the sulfur (treated with chlorine and filters)
it's great :^) I do have a seeming endless supply.

George H.
Quote:

--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


George Herold
Guest

Sat Feb 09, 2019 3:45 am   



On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
Quote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.


So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.

George H.




Quote:


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com


Clifford Heath
Guest

Sat Feb 09, 2019 5:45 am   



On 9/2/19 12:55 pm, George Herold wrote:
Quote:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.


Small volume, but the two ring magnets from an oven magnetron yields a
fairly uniform field.

Carl
Guest

Sat Feb 09, 2019 6:45 am   



On 9/2/19 12:55 pm, George Herold wrote:
Quote:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann
wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)
Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.


Two disc magnets spaced a distance of half the diameter (just like a
Helmholtz coil) gives the best homogeneity at the center of the gap.
Assuming perfect uniformity of the magnets themselves, at a guess a pair of
3" discs would give a volume with a homogeneity of maybe 0.1 to 1 part in
1000 over 1 cubic centimeter volume at a field of maybe 0.2-0.4 T depending
on the NdFeB grade. If you don't already have it grab a copy of FEMM and
run some simulations. Not great compared to 1 part in 10^8 or 9 like a high
resolution supercon NMR, but maybe enough to give a recognizable signal for
under $500 for the magnet. It's been a couple of years since I did a fair
number of sims with larger discs, playing around to see what useable volume
I could get with 6" discs for a tiny FTMS so I could be off an order of
magnitude here or there Smile.

--
Regards,
Carl Ijames


Guest

Sat Feb 09, 2019 9:45 am   



George Herold wrote:

Quote:
So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.


You mention 'yoke', and I though of the old CRT deflection yokes.
There are many kinds of those, for different defection angles,
some older ones had permanent magnet focus.
The field homogeneity in the deflection coils should be OK.
But small space inside, enough for a glass test tube though.
I have quite a bit of experience driving those, think of 10A currents,
many turns.
Should be available for next to nothing?
The older ones with magnetic focus should have a nice field too over at least some length,
Would that work?

John Miles, KE5FX
Guest

Sat Feb 09, 2019 11:45 am   



On Friday, February 8, 2019 at 5:55:29 PM UTC-8, George Herold wrote:
Quote:
So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss


You might consider offering a kit like Joe Geller's, which I
don't believe he sells anymore:

https://www.edn.com/design/analog/4392193/Geomagnetic-observatory
http://www.ke5fx.com/Geller_proton_magnetometer.pdf

In other words, instead of using specific magnets and shields to
achieve a consistent result, set up the instrument to live with (and
measure) the local field.

-- john, KE5FX

Lasse Langwadt Christense
Guest

Sat Feb 09, 2019 4:45 pm   



lørdag den 9. februar 2019 kl. 02.55.29 UTC+1 skrev George Herold:
Quote:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works..
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.

George H.


something like this? https://www.thingiverse.com/thing:942257

John Larkin
Guest

Sat Feb 09, 2019 5:45 pm   



On Fri, 8 Feb 2019 17:55:24 -0800 (PST), George Herold
<gherold_at_teachspin.com> wrote:

Quote:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.


A good NMR system has hydrogen line Qs of 1e9. To get that, the mag
field has to be uniform across the sample to a part per billion. That
leads to the arcane craft of magnet shimming.

The superconductive magnets have a few superconductive shim coils, and
a mess of (as in 10 to maybe 40) ruum temp shims, each with its own
programmable power supply.

If the sample is long and skinny, the field is expressed as a
polynomial on Z, the long axis. Z0 is the main field, and there are
shim coils to null the higher order terms. I sold a lot of gradient
coil drivers, which apply a pulsed Z1 field during the
transmit/receive sequances to do some sort of quantum mechanical
tricks.

Just the alloy and plating of the antenna coil was a trade secret, to
avoid field distortions. Screws were of exotic alloys and the hand
selected to be magnetically neutral. Tiny amounts of iron dissolved in
a sample were bad. One could buy solvents made of specific isotopes.

*Everything* is magnetic at 1 PPB.

I think NMR has been largely replaced by other technologies. It's just
a big deal to buy and install and feed a megabuck superconductive
magnet.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Carl
Guest

Sat Feb 09, 2019 6:45 pm   



"Lasse Langwadt Christensen" wrote in message
news:0f82c6e6-90eb-41ca-bca3-daf0581aa4f4_at_googlegroups.com...
Quote:

lørdag den 9. februar 2019 kl. 02.55.29 UTC+1 skrev George Herold:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann
wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it
works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.

George H.


something like this? https://www.thingiverse.com/thing:942257


It looks cute but the pictures show a lot of slop in the magnet position so
I doubt it will achieve anywhere near that field map. Not that I can
eyeball sub-part per thousand differences from a map like that but I've
spent some time playing with arrays just like that and testing small
position and tilt errors. Also, given the size of the "bore" opening
compared to the length of the magnets pretty much only a sub, sub millimeter
thick slice across the center will be homogeneous. The distance from the
closest side of the homogenous region needs to be at least two (three is
better) bore diameters from the end of the magnet segments to limit the
effect of field falloff as you approach the ends. Again, percent is easy,
sub part per thousand gets hard. You could probably shorten the magnet
length with some form of end cap but then you lose the clear bore access.
After doing a lot of comparisons I decided that just using two discs and
having side access perpendicular to the magnetic field gave the same or
greater field strength and homogeneity over an appreciable volume for the
same cost and much easier construction. I'm not a magnet physicist, this is
worth what you are paying, YMMV, etc., etc. Smile. Other things I played
with: making the discs thicker doesn't get that much more field, using a
yoke of flat plates across the outer faces of the discs with one or two side
panels gave more field but added a lot of weight and didn't really change
the simulated homogeneity so it was a wash compared to just buying thicker
discs, and trying a few simple pole cap shapes helped the homogeneity but
lowered the field since the magnets were now further apart for the same
clear gap. I was bored, curious, and had a pc and FEMM so I explored Smile.

--
Regards,
Carl Ijames

John Larkin
Guest

Sat Feb 09, 2019 6:45 pm   



On Sat, 9 Feb 2019 12:12:53 -0500, "Carl"
<carl.ijamesXYZ_at_ZYXverizon.net> wrote:

Quote:
"Lasse Langwadt Christensen" wrote in message
news:0f82c6e6-90eb-41ca-bca3-daf0581aa4f4_at_googlegroups.com...

lrdag den 9. februar 2019 kl. 02.55.29 UTC+1 skrev George Herold:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann
wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it
works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.

George H.


something like this? https://www.thingiverse.com/thing:942257

It looks cute but the pictures show a lot of slop in the magnet position so
I doubt it will achieve anywhere near that field map. Not that I can
eyeball sub-part per thousand differences from a map like that but I've
spent some time playing with arrays just like that and testing small
position and tilt errors. Also, given the size of the "bore" opening
compared to the length of the magnets pretty much only a sub, sub millimeter
thick slice across the center will be homogeneous. The distance from the
closest side of the homogenous region needs to be at least two (three is
better) bore diameters from the end of the magnet segments to limit the
effect of field falloff as you approach the ends. Again, percent is easy,
sub part per thousand gets hard. You could probably shorten the magnet
length with some form of end cap but then you lose the clear bore access.
After doing a lot of comparisons I decided that just using two discs and
having side access perpendicular to the magnetic field gave the same or
greater field strength and homogeneity over an appreciable volume for the
same cost and much easier construction. I'm not a magnet physicist, this is
worth what you are paying, YMMV, etc., etc. Smile. Other things I played
with: making the discs thicker doesn't get that much more field, using a
yoke of flat plates across the outer faces of the discs with one or two side
panels gave more field but added a lot of weight and didn't really change
the simulated homogeneity so it was a wash compared to just buying thicker
discs, and trying a few simple pole cap shapes helped the homogeneity but
lowered the field since the magnets were now further apart for the same
clear gap. I was bored, curious, and had a pc and FEMM so I explored Smile.


Maybe one could solder a bunch of unshielded drum core inductors to a
PC board and glue a couple of them to the front or back of your disk
magnets. Make an active shim system. That would allow George's system
to be a shimming trainer too.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Sat Feb 09, 2019 7:45 pm   



On 2/9/19 12:28 PM, John Larkin wrote:
Quote:
On Sat, 9 Feb 2019 12:12:53 -0500, "Carl"
carl.ijamesXYZ_at_ZYXverizon.net> wrote:

"Lasse Langwadt Christensen" wrote in message
news:0f82c6e6-90eb-41ca-bca3-daf0581aa4f4_at_googlegroups.com...

lørdag den 9. februar 2019 kl. 02.55.29 UTC+1 skrev George Herold:
On Friday, February 8, 2019 at 7:13:52 PM UTC-5, John Larkin wrote:
On Fri, 8 Feb 2019 06:05:42 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

On Thursday, February 7, 2019 at 8:12:05 PM UTC-5, Jeff Liebermann
wrote:
On Thu, 7 Feb 2019 06:33:34 -0800 (PST), George Herold
gherold_at_teachspin.com> wrote:

Hi all, A (mostly clueless) physics type wants to do
some RF stuff. (measuring nmr signals.. protons,
~5-25 MHz range) He's got something working, but
construction is ugly.

The uglier the antenna, construction, or layout, the better it
works.
https://hackadaycom.files.wordpress.com/2016/05/williams-workbench.jpg
http://hephaestusaudio.com/media/2009/05/bob-pease-breadboard.jpg

I was thinking of recommending an ARRL handbook, is
any version better than others?

I don't know. I have some old ARRL Handbook issues at home that I
rarely read or use.

5-25 MHz is practically DC as far as breadboarding is concerned.

Right... but of concern is not just bread boarding, but in nmr you
typically have a coil down the end of a probe/ transmission line and
there is some thought needed to get good coupling into the coil.

There's usually a tuning network and a low-noise (sometimes cryo, a
"chilly probe") preamp in a box just outside the main field. Some sort
of t/r switching, too, since there's only one sample coil for transmit
and receive.

So we've done things a few different ways. (Our latest nmr is all
done by Norman, and I'm mostly clueless on the details.)

Tuning near the coil is what we do now. But the first one
had a coil on a fixed length of coax, (less than 1/4 wavelength)
and a tuned series inductor for the transmitter tuning.
(I'm not sure how the input was tuned, parallel C I assume.
Norman did the hard parts here too. :^) You've got to have
some Q on the input.

So my boss asked today if we could make a cheap kit/ gizmo
that would let people 'see' proton nmr, pulse a coil,
look at the ring down. Insert water sample into coil,
see ring down change.

So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss

In a permanent magnet ~0.5 Tesla (5 k Gauss) you
can see a signal from .. well a few good sized
drops of water. at ~20 MHz.

(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)

I've got some 8" Helmholtz coils that do
~100 Gauss at 3A. But lotsa turns and spendy.

Some permanent magnets and a yoke? The field
homogeneity of little permanent magnetics is
going to suck. Field homogeneity is either
less volume or less Q, T2 broadening in the
nmr lingo.

George H.


something like this? https://www.thingiverse.com/thing:942257

It looks cute but the pictures show a lot of slop in the magnet position so
I doubt it will achieve anywhere near that field map. Not that I can
eyeball sub-part per thousand differences from a map like that but I've
spent some time playing with arrays just like that and testing small
position and tilt errors. Also, given the size of the "bore" opening
compared to the length of the magnets pretty much only a sub, sub millimeter
thick slice across the center will be homogeneous. The distance from the
closest side of the homogenous region needs to be at least two (three is
better) bore diameters from the end of the magnet segments to limit the
effect of field falloff as you approach the ends. Again, percent is easy,
sub part per thousand gets hard. You could probably shorten the magnet
length with some form of end cap but then you lose the clear bore access.
After doing a lot of comparisons I decided that just using two discs and
having side access perpendicular to the magnetic field gave the same or
greater field strength and homogeneity over an appreciable volume for the
same cost and much easier construction. I'm not a magnet physicist, this is
worth what you are paying, YMMV, etc., etc. Smile. Other things I played
with: making the discs thicker doesn't get that much more field, using a
yoke of flat plates across the outer faces of the discs with one or two side
panels gave more field but added a lot of weight and didn't really change
the simulated homogeneity so it was a wash compared to just buying thicker
discs, and trying a few simple pole cap shapes helped the homogeneity but
lowered the field since the magnets were now further apart for the same
clear gap. I was bored, curious, and had a pc and FEMM so I explored Smile.

Maybe one could solder a bunch of unshielded drum core inductors to a
PC board and glue a couple of them to the front or back of your disk
magnets. Make an active shim system. That would allow George's system
to be a shimming trainer too.


Now _that_ would be fun. If I ever retire, I hope to do that sort of
stuff--though you'd probably be limited by nonuniformities in the
permanent magnets, which wouldn't have the nice smooth variations of an
air core electromagnet.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

George Herold
Guest

Sun Feb 10, 2019 12:45 am   



On Saturday, February 9, 2019 at 5:01:01 AM UTC-5, John Miles, KE5FX wrote:
Quote:
On Friday, February 8, 2019 at 5:55:29 PM UTC-8, George Herold wrote:
So (to have fun) the first question is how big is the
sample/magnetic field? At ~2.5kHz you can see nmr in
a beer can size of water in the Earth's field ~0.6 Gauss


You might consider offering a kit like Joe Geller's, which I
don't believe he sells anymore:

https://www.edn.com/design/analog/4392193/Geomagnetic-observatory
http://www.ke5fx.com/Geller_proton_magnetometer.pdf

In other words, instead of using specific magnets and shields to
achieve a consistent result, set up the instrument to live with (and
measure) the local field.

-- john, KE5FX


Nice! I like the side by side 180 out of phase samples!
(the 180 out of phase cancels the interference noise.)
We sell an Earth Fields NMR
https://www.teachspin.com/earths-field-nmr
Instead of side by side coils it uses one
good sample coil, and a bigger, (but of the same
turns area) co-axial cancellation coil. seen in pic.
The sample is a plastic bottle, beer can size.

George H.

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