Identify chemicals with radio frequencies - Nuclear Quadrupole Resonance (MRI without magnets)

How to build and test an NQR spectrometer, which is similar to MRI, but uses no magnets. NQR frequencies are unique among all tested compounds, so detecting a resonance indicates a near certainty that a specific chemical is present.

Q/A
Why use vacuum variable capacitors? The parallel LC circuit develops well over 1000 volts during transmit, and they are much easier to finely adjust over a large range.

I've spent quite a few hours making this work since late last year. I failed to detect a signal from urea, which burned dozens of hours. Switching to NaNO2 suddenly produced a huge signal.

[bigclivedotcom]

Ben. Your videos are always ludicrously good. You need to master "shorts" to seed curiosity, then pin a link to the full video at the top of the comments. (Beware - making meaningful shorts about technical subjects is hideously tricky.)

[brunonikodemski]

I built my first NMR machine when I was in high school, in 1960, using the descriptions in a Scientific American magazine. I got an old radar magnet core (with wiring), which allowed a small volume to be magnetized. Winding some sensor coils around this zone, I was able to get a full inversion of several materials, using only an electrometer as a measuring devices. Totally useless to identify much of anything, but clearly showed the principle. This led my algebra/trig teacher to teach me some calculus, since he said I would need it in college. When I got to college I was at least three years ahead of anyone else in my classes, and aced them all. Ended up as an electrical engineer, and later integrated circuits designer. That's the value of real science.

[HuygensOptics]

Nice Ben!. Suggestion: in metal detection, they use something called a double D configuration to remove pulse signals completely. Basically you have a separate transmission and reception coil and by strategically placing the reception coil, you can remove the pulse and focus on the signal. This is something you might want to try, because it allows you to remove all the filter electronics from your setup.

[waew]

Fascinating stuff as always, Ben. And, thanks for the shout out!

[ivanpopovic]

During my final year at the university, I was called to be a part of the team designing a real NMR. They gave me the task of designing superconducting magnet. It was very fun, 9 month project that ended with working NMR device, used by chemistry department for structural molecular analysis. It is fascinating that you made working zero field device using only the basic equipment! Great work!!!

[pyromen]

I just want to say that I really appreciate what you’re doing. Every time you upload a video it’s entirely unpredictable and absolutely fascinating.

[circuitguy]

This is absolutely amazing! It's incredible to see these very complicated topics explained well and demonstrated on DIY-quality equipment.

[CuriousMarc]

This is fascinating. And the DYI wizardry is even more impressive - I didn't know this was even possible! Lots of parallels with the Cesium clock principles, but using the spin of the nucleus instead of the spin of the electron. Even the multi-pulse technique seems analogous to the Ramsey effect used in the clock, where you have two equal interaction regions separated by a period of free precession. And just like you, I also get my RF magic straightened out by watching w2aew's channel!

[frogz]

you make things that people literally study a lifetime for sound easy

[dario]

Sometimes I wonder, but yes, I was born in the right time. Thanks to all those wonderful people exploring this world and sharing their insights.

[truegret]

That's awesome. When I worked at a cargo container inspection company (using Gamma waves), we were developing device to put in all cargo containers that did a very similar technique. Broadcast, transmit (or chirp), a known spectrum, and a short time later listen to the return. With the return, we have effectively characterized that container. When we cut a small hole (1 ft sq) in the container, the return changed and we detected it. We then know there has been a container intrusion. There is more to the story of what we did after that detection ....

[AlphaPhoenixChannel]

Very cool - For some reason a "low-power-pass" and "high-power-pass" filter is something I'd never even considered. Very cool results! I love that this kind of measurement is home-shop-possible if you're patient

[discretegames]

This is the only channel where I like the videos before watching because I know I'd end up doing it anyway.

[skivvy]

This is the only channel that *Begins with the end results, and showing you. So you stick around due to respect and fascination* . Even all our other favorite channels like tech ingredients and practical engineering are guilty of saddening clickbait and shady tactics

[NROHK]

Absolutely amazed at your breadth of experiments. This one was impressive!

[BRUXXUS]

I never know what to expect by a new Applied Science video, but I do know I'll learned something and enjoy the heck out of it!

[drewf]

Wow, not only is it amazing to do NMR without a magnet, this is also one of the best explanations of NMR/MRI I've heard

[Zorndar]

One reasonable addition to increase the SNR a little could be using a differential amplifier and a pickup coil with two coils of opposing direction (1st ordr gradiometer), that way you could get rid of some of background noise. The passive lambda quarter trick was new to me, I typically work with SQUID detection of NMR signals. Great video!

[stefanm]

I worked on an MRI as an intern for 4 months and never understood how the thing worked despite talking to MRI physicists almost everyday. The way you just explained T1 time and spin echo makes so much sense I can't believe how much I just learned.

[fazergazer]

Ben. Echoing Clive’s comment: Your content has always made the most ludicrously complicated subjects accessible. I’d go as far as to say your content is in the top 0.00001% of the YouTubes for teaching. This is the best description of this practical and theoretical NMR yet. Especially like how you introduce progressive layers of understanding. Like the pulse inversion to rephase the precession. I was struck about how these phenomena have analogous (though not physically arising from the same cause) in optics. Like the phase-conjugate mirror used to demonstrate a laser cavity where one mirror was replaced by a highly non-ideal reflector made from a spatula. The beam automatically tracked the spatula as it was moved about the lab. Anyway, I was a structural biologist and used NMR, x-ray diffraction, and related techniques along with lab-directed evolution using GFP-based folding and solubility reporters, including the “shazam” split GFP tagging systems I developed, now used by other labs to probe the hidden life of molecules in living systems and make new biosensors. I wish your content would have been available in graduate school. cheers!