DIY cloud chamber

Cloud chamber is a device that can be used to detect/show cosmic rays (particles from the universe). Cosmic rays are harmless and are invisible to us. Presence of cosmic ray will show a trace/track that run across inside the cloud chamber.

I get to learn how to make a cloud chamber from NUS High School of Math & Science. The video here show our DIY cloud chamber and the trace of cosmic ray. In the DIY cloud chamber, the trace cause by the ray look like shooting stars.

While in a real cloud chamber, the trace look like fire works. Partly because we purposely put an radioactive material in the middle to create the cosmic ray so we do not need to wait too long to see its trace. Here's the video of the real cloud chamber.

Here's the brief instruction on how to make your own cloud chamber. Making it is easy however you may need to buy absolute isopropyl alcohol (pure / >99%) which may not be available commercially. You need to get it from those chemical supplier.

*Do note this isopropyl alcohol is denatured type, so do not drink it if you have excess of it from the experiment.

Things you need:

1) A clear plastic container (we use those tea bag container (w lid) from Ikea, but we don't need the lid)

2) Wooden Tray / shallow styrofoam box that is bigger than the clear plastic container.

3) A big piece of felt / absorbing cloth (available from Daiso)

4) Aluminium plate with black epoxy coating slightly bigger than the clear container but still able to fit into the wooden / styrofoam box.
*Paint coating aluminium is not suitable as it will peel off when contact with dry ice for too long.

5) Strip of LED light (length = perimeter of the clear container)

Procedure:

1) Roll up the felt and stick around the bottom of the clear container. We drill hole onto the container so string can go through and tied the felt to the container. As the felt must be able to stick there and not dropped when wetted with isopropyl alcohol.

2) Cut a rectangular felt where the perimeter is the same as the clear container (to seal the gap between the container and the aluminium plate)

3) Put dry ice in the wooden / styrofoam box.

4) Put the black aluminium plate on top of it.

5) Wet the rectangular felt and the felt inside the container with isopropyl alcohol. Do not add too much till the alcohol is dripping.

6) Invert it and put on top of the black aluminium plate

7) Put the LED light around it.

The coldness from the dry ice will cause the vapour to condense to form small droplets. When the ray pass by, these droplets will form track which you have seen it in the video.