



My radioactive vacuum tube uses radium lume.
I recently picked up this radioactive vacuum tube, I couldn't find what isotope it used online but I deduced it wasn't a gas since it's more radioactive at one end than the other. Today I was shining my UV light on it, for some reason, and I noticed some fluorescent dust at the bottom, upon closer inspection it turns out there's just a blob of radium lume on the cathode.