Greetings fellow nerds.
Today I'm going way outside of chemistry and into nuclear physics with this review of the Radiacode 103 gamma spectrometer.
You can buy these things right now directly from the company for 300 euros or 325 USD and I think you can also get them off amazon as well.
So what does it do? It measures radiation.
But if that's all it did, it'd be overpriced and boring and I probably wouldn't bother.
But what sets this apart from the usual geiger counter is that it's a gamma spectrometer.
So what's the difference and why is that important.
A geiger counter measures radiation by counting the events when a particle of radiation interacts with it, and this tells you the intensity of the radiation.
They are widely available and easy to obtain for reasonable cost.
But the information they give is rather limited, it's just the intensity.
While this does tell you the presence of radiation and can be useful for warning you of radioactive dangers, or measuring the presence or concentrations of radioactive materials.
It's like seeing the world in black and white, there is a lot of information you're missing.
A spectrometer is a major step up and actually measures the energy of the individual particles being detected, not just that they are there.
By plotting them you can get a spectrum and because each radioisotope has a unique spectrum this can help identify it.
It's like seeing the world in color.
Commonly available geiger counters just tell you something is radioactive, but not really what it is.
The radiacode can because it's a spectrometer.
So here it is, fairly straightforward, I must say I'm impressed with just how small it is.
You can inconspicuously keep this with you on your person at all times and keep tabs on the radiation around you.
The detector crystal is located here, in between the radioactive symbol on the front and the plus sign on the back.
It's a block of cesium iodide and i'll open this up to show it to you later in the video.
Now because the detector is behind a few layers of plastic, the radiacode cannot detect alpha particles as they don't effectively penetrate the plastic.
Beta particles are also attenuated by the plastic shielding and beta particles in general have broad continuums of energies rather than sharp peaks.
And that makes them difficult to distinguish from the background.
So the real value of the radiacode is as a gamma spectrometer.
And since most radioactive isotopes or their daughter products do emit small amounts of gamma radiation or secondary x-ray emissions,
they can all still be identified with the radiacode if sufficiently intense.
It's battery powered and can last for a few days so you can collect a lot of data out in the field between charges.
You can control it using the three buttons on the unit but i'll be honest i found them cumbersome and the display cramped.
The much better user interface is the smartphone app that can be used to control all aspects of the device.
Here we can see the accumulated radiation dose, which is useful if you want to use it as a dosimeter.
And we see current radiation intensity as well as a history of radiation levels.
There is also a mapping function when used with your phone to map out radiation levels as you travel.
Here you can see me driving through a city and measuring the radiation on my trip.
If the fallout TV series becomes a reality show then we'll need this to map out safe areas or plot out the dangerous ones.
But so far these functions are already performed by cheaper geiger counters,
the real star of radiacode that sets it apart is the gamma spectrometer function.
As radiation photons are detected and measured the energy is plotted here on a spectrum.
It takes time to accumulate enough signal to distinguish the unique peaks.
But when you have enough you can identify the isotope generating that spectrum.
A great feature of the radiacode is that it already has a library of common isotopes so if you tap and hold on a peak the app will try and match it.
But i found the phone app a bit hard to use for this since i fat fingered a lot of the peaks.
Fortunately there is a desktop computer app for the radiacode where we can open spectra and analyze them.
The radiacode can be connected by USB and similarly controlled just like with the phone app.
Okay i've gone on long enough showing it off, let's use it.
Right now the radiacode is just measuring the background radiation in my lab.
This is about 3 to 4 counts per second.
So anything we measure is going to need to produce a higher count rate than that for us to distinguish it from the background.
I'm going to leave this here for a few hours to accumulate the several thousand counts necessary to obtain a good spectrum.
Now i've connected it to my computer and downloaded the data and we can see the spectrum of background radiation in my lab.
It's a nice continuum and knowing this we have a baseline for which to compare so we can distinguish peaks of actual samples.
So let's try something actually radioactive now.
I got here thoriated tungsten rods used for welding.
They contain about 2% thorium and are easy to buy.
Let me put the sensor on it, and whoa, that's several times background radiation.
I'm going to leave it there to accumulate enough data to analyze.
And here we are some hours later.
These peaks on top of the background correspond to the various gamma emissions.
The awesome thing about the radiacode isotope library is that if you highlight one of the peaks,
it gives you its best guess and also displays bars that correspond to other expected peaks in that decay chain.
This is very useful for identifying an isotope as you can match it up a spectrum with the expected spectrum.
So you can see here all the positions in the thorium library match up with the actual thorium spectrum.
And so we can conclude these thoriated tungsten rods are authentic and not some knockoffs.
Now at this point i want to emphasize the true usefulness of a spectrometer as opposed to a counter.
It can help us identify an unknown radioisotope.
So i have here a sample of dried berries and according to the counter it's radioactive, definitely at a higher rate than the background.
But if this was just a counter then all we would know is that it's radioactive and not much else.
So i'm going to let it collect data for the next few hours and hopefully we can identify it.
And here it is on the computer and we can identify it as cesium-137.
Cesium-137 does exist in trace amounts in nature, but for it to exceed the signal of naturally occurring potassium there has to be a significant amount of it.
The only source of that much cesium is nuclear fallout
so this sample of dried berries was likely grown somewhere in Europe on soil that was contaminated with the fallout from the chernobyl nuclear disaster back in 1986.
The contamination still lingers to this day.
Fortunately it's pretty small.
It's not great, but not terrible.
So you can see the value of a gamma spectrometer as opposed to a geiger counter.
It can tell us what the isotope is and give us insights as to where something came from.
This can even be used to authenticate things like vintage wines from before the atomic age.
If there is radioactivity from nuclear fallout then we know the wine is likely fraudulent.
Although i'm not sure if the radiacode is sensitive enough to measure something like wine.
Now i'm very curious as to the design of these things so I got one to take apart.
It has all the expected parts like microcontrollers, LCD, speaker, bluetooth transceiver and other electronics.
Most of the same electronics you'd find in a cell phone, just reprogrammed and repurposed to be a gamma spectrometer.
But the real science happens here in this tiny black component.
This is the actual gamma ray sensor.
Let me open it up.
And there it is.
This is a scintillation counter.
The white cube i'm holding here is a crystal of highly pure cesium iodide doped with a tiny amount of thallium.
It's actually encased in a protective coating and the crystal itself is seen through this window.
When gamma rays go through the crystal they ionize it and the recombination of charges causes the crystal to generate a pulse of light.
The intensity of the pulse is proportional to the energy of the gamma ray photon and so all we have to do is measure that pulse for each photon
and that gives us a way to measure gamma ray energy.
The measurement is done with this solar cell looking device over here.
It's actually a solid state photomultiplier to amplify the pulses to a level that can more accurately be measured.
A simple solar cell or photodiode might work, but the signal is very weak so amplification is often necessary.
Anyway, that's the gamma ray sensor.
I must say I'm impressed how something so small and simple can measure something so tiny as a single gamma ray photon.
Most gamma spectrometers I've ever used are the size of shoeboxes.
All of that functionality has been crammed into this tiny device.
Unfortunately i've pretty much destroyed the sensor by opening it up like this,
so if you have a radiacode be content with my teardown video and don't open up yours if you want to keep using it.
Fortunately I have a second one so I can keep doing experiments.
Let's try something else now and I'm going to measure potassium chloride which contains tiny amounts of naturally occurring potassium 40.
Okay it looks like there is very little signal with this beaker full of it.
I suppose that's a good thing since I don't want my bananas irradiating me.
But it does mean we need a bigger sample.
So I'm going to put the radiacode right on the whole bag of potassium chloride.
And it looks like there is a decent signal at over 10 counts per second.
Not as much as the thoriated tungsten rods but still about triple that of the background.
I'll leave it there overnight to try and get a decent spectrum.
And here we are, and that peak there is the potassium-40 isotope peak.
It's a single peak without any daughter products and is often used to calibrate gamma spectrometers.
Now looking at the spectrum you might be wondering what this peak edge here is.
It's bigger than the potassium-40, but it seems to be a continuum.
Some of it is background radiation but we saw that the potassium signal was intense enough to double or triple the count rate of the background.
So if this was entirely background it shouldn't be that large.
Looking at the library the closest peak is cobalt-60, but cobalt-60 has two distinctive peaks, and this is just one.
So this is likely not cobalt-60.
I thought it might have been beta radiation since potassium 40 makes a lot of beta particles.
So I put a 3mm copper shield in front of the radiacode to block all beta particles but the spectrum changed very little.
So the plastic casing alone had already blocked or attenuated most of it.
So what's happening here? This is an effect called Compton scattering, and this edge here is known as the Compton edge with the rest of the radiation being called the Compton continuum.
What's happening is that not all the gamma rays are absorbed into the crystal, a great many of them will scatter off the crystal and only deposit a portion of their energy, with the rest escaping.
So this continuum of radiation isn't a true signal from the radioisotope, but sort of a mirage happening inside the detector.
By knowing this we can ignore it as a false signal.
We actually saw this earlier in the thorium spectrum but there were a lot of legitimate peaks from daughter isotopes so I wanted to focus on those.
Anyway, there are techniques to suppress it like using another scintillator to detect the escaping photon and thus ignore the signal.
Alternatively the brute force solution is to use a huge fist size crystal so the gamma photons can't escape at all.
Unfortunately the radiacode is too small to be able to implement those solutions.
But I think that's a fair trade for such a portable and modestly priced device.
Now I want to go back to the thorium spectrum because I noticed something amazing about it after I acquired 2 days of signal.
This tiny peak here is another unusual peak that doesn't correspond to a true gamma emission.
At first I confused it for the Compton edge, but after acquiring a couple days worth of data I realized it was a separate peak and the radiacode was able to resolve it.
This is what's called a pair production escape peak.
If the gamma rays are high enough energy, greater than the rest mass of two electrons, then upon interaction with the detector there is a chance they produce an electron-positron pair.
If one of them escapes the detector before annihilating then that shortfall of energy appears as a peak that's lower than the mass of the escaped particle.
And that's why it's called a pair production escape peak.
We see the primary photon peak up here at 2614 keV, and we see the escape peak here at 2103 keV, which is exactly the difference of one electron rest mass at 511 keV.
I'll be honest this blows me away, we are seeing in the data the effects of energy to matter conversion.
Nuclear physics is amazing, in another universe I might have been a nuclear physicist and my youtube channel would have projects to make nuclear reactors in my basement rather than sodium.
But unfortunately in this universe you're stuck with me.
Now I want to try something most of us have, a smoke detector.
Americium-241 is often used in smoke detectors as an ionization source.
The vast majority of the radiation is in alpha particles that don't leave the detector, but a tiny amount is in gamma rays that we can measure.
And wow, that's a good 80 to 90 counts per second.
That's the most intense radiation i've measured so far.
Anyway, as usual I left it for a few hours to accumulate enough data and there is our spectrum.
We can clearly see the two distinctive gamma ray peaks.
They are much lower energy than the other isotopes we've seen so I had to zoom in on this part of the scale.
You'll also notice the peaks don't perfectly match up with the isotope library.
I found the radiacode to be slightly inaccurate at lower energies and even if i calibrate to the lower energies there are other inaccuracies at the higher energies.
But overall the inaccuracies are minor and maybe i'm just not doing the calibration properly.
We're still getting awesome results.
And I have been told that even professional units sometimes require frequent recalibration for spectra of interest.
Finally I want to demonstrate the interesting isotope of tritium.
These are radioluminescent tritium lights, and are powered by the beta decay of tritium.
The amount of tritium in each one is substantial enough to generate light as the beta radiation strikes the phosphor and causes it to glow.
Now tritium decays purely by beta decay without a gamma component so this shouldn't normally produce gamma radiation.
And the beta particles are extremely low energy, they are unable to penetrate the glass and so nothing should be detected.
But the radiacode looks like it can detect something.
What's happening is the beta particles themselves are producing a type of x-ray emission called bremsstrahlung when they strike the glass.
These x-rays are detectable by the radiacode but because they are a type of secondary x-ray emission and not technically gamma rays they are not in the radiacode library.
The peak value of 12 keV is likely wrong due to inaccuracies at these low energies but i'm amazed we can detect something as weak as tritium bremsstrahlung.
So that was the radiacode 103 gamma ray spectrometer.
I think it's really cool and tremendously useful for being able to get an energy spectrum for gamma radiation and not just detect it.
We can use that information to identify unknown radioisotopes.
And the resolution is good enough to distinguish weird effects like pair production.
Overall i'm quite impressed with it and who knows, now that I have it I might be inspired to try some nuclear chemistry in the future.
Thanks for watching.
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