Making a cloud chamber to see radiation without needing dry ice

Seeing radiation with your own eyes is incredible. It wows everyone who sees it, and is a perfect ‘hook’ to bring people over to your nuclear education table. “Hey, you guys want to see some radiation?”

I’ve used a normal dry ice cooled cloud chamber many times in science demos at corporate family nights, at demo tables at the Pacific Science Center, at schools, and so on for many years. You can still find dry ice at a number of grocery stores, but it seems to be getting more difficult. Plus, the dry ice runs out after a few hours, and you have to get more. I’ve heard of people using thermoelectric cooler (TEC) pads for this and thought I should try it out.

The thermals for my first consistently cold-enough stack.

Equipment List

Cooling pads

I’ll be honest, I bought lots of TECs of various sizes and combinations before finding a combo that worked for me.

Power supply

I used a 500 Watt computer power supply for this, since they can provide quite a bit of current at 12V, 5V, and 3.3V. I spent some time attaching Anderson power pole connectors to it for convenience during experimentation.

Water cooling

After struggling to get temperatures down for so long, I decided to just go straight to direct once-through water cooling until I got it all working. I got an aluminum water block, some tubing, and some faucet connectors, so I could just run it right out of a normal household faucet.

Once-through water cooling isn’t ideal for portability, since you have to be near a water supply and drain. I will try to find a big enough air radiator to get this to work without a direct water connection later.

Cooling tests

It took a lot of experimenting to get the thing cold enough. First I tried a CPU cooling radiator. This got me to the right temperatures if I went outside with a stack of three TECs but was hard to reproduce.

This still seems like a great configuration but I think I broke some of the TECs by clamping down too hard on them.
Uh yeah that’s a broken TEC

Really stretching with the water cooling. This was a dumb idea because at 400W you basically heat the bucket of water up in a few minutes

Getting more serious with once-through water cooling, lol.

Ooooh yeah now we’re talking
Pretty chilly
With the rock on it
Now working

See also

There are a number of good builds out there that were very helpful.

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