Visualising radioactive decay with Cloud Chambers (Part 1: How it works)

Atoms are decaying around us every second. Traces of radioactive Carbon-14, minute amounts of Radon-222 in the air. Yet, we don't feel or see their effects. In fact, particles produced by decay is charged and can trigger some sensitive processes. In the cloud chamber, the alpha and beta particles can trigger the condensation of alcohol vapour to form trails! In the above video, an alpha source is placed in the chamber and the distinct trails can be seen!

A cloud chamber usually uses dry ice to operate, as the alcohol requires around -25 deg C to become supersaturated. The cold air is able to hold little alcohol vapour, so any small disturbance causes condensation to occur.

The thick trails correspond to alpha particles, which are heavy and not easily deflected. On the other hand, the thin squiggly trails correspond to beta particles. These trails come from background radiation alone! A small Geiger counter will tell you that the background radiation can give about 1-2 counts per second. With a large enough cloud chamber, we can visually see all this.

All of the above pictures are not mine. However, I have made my very own cloud chamber! In my next post, I will show how to construct it without dry ice - using just normal ice and thermoelectric coolers. I will also show some of the trails I got with my homemade cloud chamber.