In high resolution, a thorite of low activity in the cloud chamber with a strong magnet beneath the surface (the field is in the left side, in half the active surface). The strength of the magnet was purposely reduced by setting it distant of the surface to not curve too much the electrons.

The Rn 220, a radioactive gas, comes from the Th 232 decay chain. The gas fill the chamber then it decay into Po 216 emitting an alpha particle. This nucleus is very instable, it's half-life is 0,14 seconds. It decays almost instantly into Pb 212, emitting an alpha particle. The Pb 212 nucleus is more stable (half life 10,6 hrs). We thus see 2 alpha tracks coming from the "same" origin, the first from Rn 220 to Po 216 and the second from Po 216 to Pb 212, which makes the characteristic "V" in the cloud chamber.

The Rn 222, also a radioactive gas, comes from the U 238 decay chain. The gas fill the chamber then it decay into Po 218 emitting an alpha particle. This nucleus is much more stable than the isotope Po 216 because it's half-life is 3 minutes. So we see only one single alpha track because the Po 218 don't disintegrate in the almost same time like Rn 222.

As the stones come from Colorado, this time the music is more ... country like !

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