Electrically cooled cloud chamber

This cloud chamber allows you to see tracks from individual alpha and beta particles.

Dry ice based cloud chambers are quite common, you cool a plate at the bottom and create a chamber full of alcohol vapour. The vapour cools as it falls and eventually becomes supersaturated, and any ionising radiation creates tracks of cloud. They are great, but dry ice is a pain to get hold of.

I was asked to build a cloud chamber for the Museum of Science and Industry. They wanted one which didn't need the dry ice as the way it sublimes all the time makes it logistically difficult to deal with, especially as it is a cryo-hazard. So I built a cloud chamber using peltier coolers. These are small, electrical heat pumps which would be ideal for the job if they weren't quite so inefficient. With a lot of heat sinks, and fans, the resulting chamber produces nice tracks from the alpha particles given off by the thorium in a small piece of gas mantle.

Cloud ChamberCloud Chamber

And here are some particle tracks

If you are interested in more about how a conventional dry ice cooled cloud chamber works, I wrote it up on the Naked Scientists