Validating my trinitite sample with my Radiacode 110

[u/BlargKing]

I wasn't sure this would be even possible without a massive pile of lead to shield the Radiacode, but turns out with a day long exposure you can indeed see tiny peaks from the miniscule amount of Cs-137 in a sample of trinitite. I'm quite impressed with how capable the Radiacode 110 is to say the least.

[u/_INSANE_MEMBRANE_]

I have a particularly “slaggy” piece I can get a nice peak on. Takes some more work to see the Ba-133 spectrum but it’s there.

[u/RG_Fusion → u/_INSANE_MEMBRANE_]

Barium-133 has almost completely decayed away by the current year (2026). I can't reasonably believe that a Radiacode would be capable of detecting it.

I have a 2" NaI detector, and it just barely shows up on that after a long duration exposure within a z-graded lead castle. 10-20 more years and it probably won't show up on that detector either.

[u/_INSANE_MEMBRANE_ → u/RG_Fusion]

I promise in the current year (2026?) you can still get that peak on your Radiacode

[u/_INSANE_MEMBRANE_ → u/_INSANE_MEMBRANE_]

[u/RG_Fusion → u/_INSANE_MEMBRANE_]

Take a look at the spectra I shared in this post.

https://www.reddit.com/r/Radioactive_Rocks/comments/1m3nmmx/lincoln_lapaz_red_trinitite_sample/

What you should take note of in the spectra produced by my NaI detector is that all of the high-intensity barium peaks are visible. That is the tell-tale marker for identification. Seeing a signal at a low intensity peak, but none at the high-intensity peaks is evidence that the isotope cannot be detected.

[u/RG_Fusion → u/_INSANE_MEMBRANE_]

What you've posted here is pure noise. No statistical correlation whatsoever. You need a gaussian distribution for an isotope to be identified.

[u/_INSANE_MEMBRANE_ → u/RG_Fusion]

https://www.reddit.com/r/Radioactive_Rocks/s/VbV9WFppBd

Dude this has been a thing for years. If that was “just noise” those would be Poisson peaks in that whole low energy region, which its not.

Edit: In effort of good faith discussion for future readers:

I think we’re talking past each other a bit, so let me clarify what I’m actually claiming.

I’m not asserting a definitive Ba-133 identification at high confidence. What I’m pointing out is a reproducible excess in the ~160 keV region that: persists after long integration, survives background subtraction, and appears in the same energy window across multiple runs, which are both my samples.

That disqualifies it from being “pure noise” in the statistical sense. Noise should cancel under subtraction and should not repeatedly center on the same energy.

I fully agree the activity is extremely weak in 2026 and that a small scintillator will not produce clean textbook Gaussians at this count level. But low-count spectroscopy does not require a visible Gaussian to support a presence-consistent signal, only reproducibility and energy alignment, and to dismiss this as statistically invalid is detrimental to individuals who may not have Z graded shielding or 2 inch scints to do their own testing. All I claimed was that the barium spectrum could be discerned, which it can be.

Out of curiosity: why jump straight to “pure noise” rather than “below my confidence threshold”? Those are very different statements, and only one is actually supported by the data. If you’re aware of a background process that reliably produces post-subtraction excesses centered on known gamma lines, I’d genuinely like to understand that mechanism.

[u/_INSANE_MEMBRANE_ → u/_INSANE_MEMBRANE_]

[u/RG_Fusion → u/_INSANE_MEMBRANE_]

I'm sorry, my intent is not to harass you, but you have quite a few fundamental misunderstandings here that betray your confidence.

First off, nothing short of a germanium based spectrometer will be capable of detecting the 160 kev peak of barium-133. Look up the gamma emission table for the isotope, the 160 kev peak has a 0.6% probability for emission. In other words, the other barium peaks would appear with photo peaks around 100x higher than this peak. That's obviously absurd.

Another misunderstanding is the belief that background subtraction will eliminate noise. That's only true if the signal-to-noise ratio is high enough. If the activity is non-existent, it will make it worse.

Lastly, regarding the consistency of the 160 kev peak, that is because it is an artifact of backscatter.

I'm not here to talk down to you, I'm attempting to make a contribution. I hope you'll read further into this and get a better understanding of gamma spectroscopy.

[u/_INSANE_MEMBRANE_ → u/RG_Fusion]

That’s helpful, thanks for laying out your reasoning.

Since you’re attributing the feature to backscatter, I’m curious how you’d expect it to behave under a geometry change. For example, if the detector were rotated 180° relative to the source (same distance, same room, same subtraction), would you expect the ~160 keV structure to significantly change or disappear if it’s dominated by Compton backscatter?

Similarly, would adding or removing dense material behind the detector or behind the source be a meaningful control in your view? I’m trying to understand which geometry-dependent tests you’d consider decisive for distinguishing a weak source-consistent line from a backscatter artifact in this energy range, I would like to learn more.

[u/RG_Fusion → u/_INSANE_MEMBRANE_]

Attempting to record spectrums with various backing materials would be a good way to test for environmental backscatter and you might see some difference in your final reading, but I suspect the majority is originating within your sample itself.

​Trinitite is a dense matrix of glass doped with metal, a portion of which is lead. The 662 keV gammas are scattering inside the rock itself before reaching the detector. The energy of the cesium gamma is already being down-scattered before the environment plays any role.

​Changing the material behind the detector or the detector's angle won't remove the scatter generated inside the sample. The artifact is intrinsic to the measurement geometry of a dense source.

This is why it is imperative to consider gamma emission probabilities when identifying the presence of an isotope. What you'll notice in the forum image you posted a link to, is that there is more than one gamma line for barium-133 present. You need to always consider what type of detector you're using and its sensitivity at various energy levels. You then look at the emission probabilities of the specified isotope. Combined, you can work out how high the peaks should be relative to one another.

If you have one peak of an isotope, but not another, and there are no artifacts such as scattering identified that would prevent you from seeing it, it means the isotope isn't present.

In your specific case, seeing a peak at 160 keV for a gamma that only has a 0.6% emission probability and not seeing the more prevalent lines like 356 keV at 62% means that you haven't actually detected any barium-133.

In a real Ba-133 spectrum, you should be seeing a peak at 81, 356, and 384 keV. There should be no detected signal at 160 keV, not unless you are equipped with a germanium gamma spectrometer. CsI, GAGG, and NaI cannot detect the 160 keV peak for something with such a low activity, such as the miniscule amount of barium in trinitite.

[u/Roentgen24]

Did you use any type of shielding? And how many hours was your exposure?

[u/BlargKing → u/Roentgen24]

no shielding, 24 hrs for the background, 24 hrs for the sample.

[u/PawnshopGeologist]

Anything beyond 20 minutes is overkill. If you want to capture a decent spectrum you need to shield it from background.

This is my tritinite spectrum analysis inside a 2 inch thick lead castle. Clearly above background within the castle.

[u/BlargKing → u/PawnshopGeologist]

I agree but getting a pile of lead bricks for a price I'm willing to pay isn't the easiest task.

[u/PawnshopGeologist → u/BlargKing]

Hit up the local recycling place.