Making Clouds and Seeing Particle Tracks

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Once we got the cloud chamber built, we tried to make clouds with it. The cloud chamber sits on the marble tile, which sits on top of the dry ice - the fish tank that makes up the chamber sits upside down on the tile.  We glued a felt pad to the bottom of the fish tank and then soaked it in ethyl alcohol, which is supposed to make good particle droplets.  The key is that the drops have to be small enough to rain down from top to bottom like, fog, but not so big that they fall like rain.  The radioactive particles we are trying to see should make a trail through the fog that we can see.

We learned that the fog won't happen fast enough without putting something hot on top of the fish tank.  This discovery cost us a whole week, but we felt like we were getting close.

It really made sense to us that we needed to use the hot pad on top of the tank - when the earth makes fog, the sun is the energy source that makes water evaporate into tiny droplets.  As they fall through the cooler atmosphere, the droplets can join together to make droplets of fog.  

It turned out to be really hard to see the particle tracks we were after. We thought we saw some, but it was very difficult to see them on the video we took. You can see how hard it was to get the lighting just right, but we definitely thought we saw tracks from radioactive particles.