u/NorthComparison4356

Hey folks,

I’ve been playing around with my gamma spec setup (amateur, low-fi) and wanted to share a result that taught me something new.

Background: Here in southern Bavaria, some areas still have detectable Cs-137 from Chernobyl in forest soils, wild boar, etc. I’ve personally measured it in my garden soil. So when a neighboring farmer gave me a sample of fresh raw milk, I thought – why not see if any shows up in the milk?

The result:

• No Cs-137 peak at 661 keV above my (unknown) detection limit. So that’s reassuring.
• But: I see an additional ~4800 counts in the X-ray/low-energy region (roughly 50–200 keV) compared to background (pink curve).

It’s not distinct peaks – it’s a broad continuum. Classic Bremsstrahlung shape. (And yes, I love that English just borrowed that German word - Arnold Sommerfeld, 1909)

My interpretation:
I’m indirectly seeing beta emitters in the milk. Fast electrons from beta decay get deflected by the aluminum housing of my detector (or other surrounding materials) and produce that continuous X-ray spectrum. If I had a proper HPGe, I might resolve some characteristic peaks within that continuum, but with my amateur setup, it’s just a noisy, weak excess.

The big question – which beta emitter?
Most likely candidate: K-40. It’s naturally abundant in milk (potassium). The gamma line at 1460 keV (10.72% branching ratio) wasn’t elevated above background, but that’s not surprising – the beta emissions are the dominant decay mode. So what I’m probably seeing is Bremsstrahlung from K-40 betas. Or you have any other explanation?

Takeaway for other amateurs:
Don’t just stare at the photopeaks. That low-energy continuum can tell you a story too. It’s pretty wild that we can indirectly “see” beta emissions in a gamma spectrum, even with a humble setup.

Anyone else seen similar effects in food samples? Could anything else (natural Po-210? fallout Sr-90?) contribute to beta activity in fresh milk around here, or is K-40 the only realistic culprit?

Cheers from Bavaria ☢️🥛

Hey everyone,

Just had to share my newest acquisition—a beautiful specimen of Antozonite (often called Stinkspar or fetid fluorite) that I was lucky enough to source locally here in Germany. The piece measures about **6.5cm x 5cm x 1.5cm**, and its deep violet-black color is absolutely captivating. But of course, for folks in this sub, the real excitement is what's inside.

I put it under my gamma spectrometer, and as you can see from the spectrum, it's a lively one. It shows a very clear Ra-226 signature, which I'll dig into below.

So, what makes Antozonite so special?

For those unfamiliar, this isn't just your average purple fluorite. This stuff is the *only* known place on Earth where you can find naturally occurring, **elemental fluorine (F₂)** gas.

The "Stink" Factor: When crushed or broken (DONT DO THAT, LOL!), it releases that trapped F₂. The fluorine then reacts with water vapor in the air to produce ozone (O₃) and hydrogen fluoride (HF), which gives it a pungent, unmistakable stench that has been noted since the 19th century. The smell has famously been described as anything from "garlic-like" to, at high dilution, "like a perfume".

The Violet-Black Color: That intense, nearly black coloration is a direct result of its radioactive past. The mineral contains tiny inclusions of uranium, which over eons have bombarded the fluorite (CaF₂) with alpha and beta radiation. This radiation creates "color centers"—defects in the crystal lattice, specifically clusters of calcium atoms (colloidal calcium), which absorb light and give the mineral its deep purple to black hue.

The Formation of F₂: This is the coolest part. The high-energy beta particles from the decaying uranium split the calcium fluoride (CaF₂) into calcium and fluorine atoms. These individual fluorine atoms then pair up to form diatomic fluorine gas (F₂), which becomes trapped as tiny inclusions within the crystal structure. It wasn't until 2012 that scientists using solid-state NMR spectroscopy finally proved that the gas inside was, in fact, elemental fluorine, settling a nearly 200-year-old debate.

The Gamma Spectrum (Ra-226)

I mostly see the Ra226 decay chain, maybe some shoulders in the Xray could be from U238 (Th234)? Also one peak marked as U235?? Don't know if that is correct. And again that Barium Xray at 32keV-ish.

I think it is a cool specimen of mineralogy, and nuclear physics all wrapped up in one smelly, radioactive package.

While this specimen is mostly safe to handle and store, I would avoid crushing it and sniffing that stuff. Apply hygiene and common sense :-)...

I just need to vent to people who will actually understand my pain.

I built a lead castle a while back – got myself about 85% reduction in background radiation. Mehhh.... that last 15% kept staring at me. So I decided to go for it. Wanted to smash that 90% barrier.

Here's what I did:

• 3D printed a bucket in PETG
• Sealed it with fast-reacting epoxy
• Filled it with 15kg of 3mm lead balls
• Fixed everything with more epoxy
• Added a bottom plate with 20mm of lead sheet (same method)

Total additional lead: ~15kg + 20mm sheet. Shipping alone was $60. Poor delivery guy, 25kg on the total parcel weight.

The result? I barely cracked 90% reduction. That's it. From 85% to maybe 90% on a good day.

I attached the spectrum (green = unshielded, running 103 CPS). You can clearly see the Rn222 decay chain and K40 just laughing at me. Those high-energy gammas don't care about my little lead fortress.

I guess this is the reality check: background radiation is pesky. Getting to 95% reduction would probably require another order of magnitude more lead, and my wife staring at me....

Has anyone here actually hit 95%+ reduction with a home setup? Or should I just accept that K40 and cosmic secondaries are always going to win?