Here's How To Build Your Own Cloud Chamber To Detect Particles

Particles are zipping past you all the time, and you don't even notice it happen. Here's how to quickly build a cloud chamber so you can detect these particles in your own home!

All four types of particles detectable in a cloud chamber. Image credit: Cloudylabs


Symmetry Magazine, the fine folks who brought us patterns to cut physicist-snowflakes for holiday decorating, are back at it with awesome Do-It-Yourself projects. This time it's how to use a glass tank, felt, some isopropyl alcohol (medical alcohol, not drinkable booze!), and a cooling system (dry ice; handle with care) to build a cloud chamber. The directions are simple: cut the felt to fit the tank, soak it in the alcohol, seal the inverted tank with dry ice cooling it from the bottom, flip off the lights and watch the magic happen.

As the alcohol evaporates, it saturates the air in the tank. Yet the cooling from the ice drops it below the dew point, condensing the alcohol into a misty fog. As cosmic rays and other particles dart through the foggy tank, the particles occasionally knock off an electron off an air molecule, creating a charged ion. The alcohol vapour is attracted to the ions, condensing to create a visible trail marking the particles' paths.

The real fun comes after your project is built: identifying the particles zipping through your alcohol vapour. This is a quick and dirty guide to common particles:

  • Short & fat are alpha particles
  • Long & straight are muons
  • Zig-zags & corkscrews are electrons or positrons.
  • Forked paths are from the moment of decay, when one particle decays into more stable components.

I've been hypnotized every time I see a cloud chamber. Surely, building a sealed tank with an electric cooling unit would be the ultimate in geeky coffee tables!

Read more on Symmetry Magazine for detailed instructions, physics, and awesome illustrations.


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