See The Radioactive World With This Peltier Cloud Chamber

Remember when a homemade cloud chamber was a science fair staple? We haven’t participated for decades, but it seemed like every year someone would put a hunk of dry ice in a fish tank, add a little alcohol, and with the lighting just right – which it never was in the gymnasium – you might be lucky enough to see a few contrails in the supersaturated vapor as the occasional stray bit of background radiation whizzed through the apparatus.

Done right, the classic cloud chamber is a great demonstration, but stocking enough dry ice to keep the fun going is a bit of a drag. That’s where this Peltier-cooled cloud chamber comes into its own. [mosivers] spares no expense at making a more permanent, turn-key cloud chamber, which is perched atop a laser-cut acrylic case. Inside that is an ATX power supply which runs a Peltier thermoelectric cooling module. Coupled with a CPU cooler, the TEC is able to drive the chamber temperature down to a chilly -42°C, with a strip of white LEDs providing the required side-lighting. The video below gives a tour of the machine and shows a few traces from a chunk of pitchblende; it’s all pretty tame until [mosivers] turns on his special modification – a high-voltage grid powered by a scrapped electronic fly swatter. That really kicks up the action, and even lets thoriated TIG welding electrodes be used as a decent source of alpha particles.

It’s been a while since we’ve seen a Peltier cloud chamber build around here, which is too bad because they’re great tools for engaging young minds as well as for discovery. And if you use one right, it just might make you as famous as your mother.

17 thoughts on “See The Radioactive World With This Peltier Cloud Chamber

    1. Awesome design, I was ordering parts (lots of acrylic sheets) when I came across this and realized 5×10 domed jars on Amazon are like $15 along with just how much better they are for multiple projects.., better than building an acrylic tank, Best of all this solved my design for an upcoming vacuum chamber build for a small fusor as I can now use the glass for both cloud chamber and vacuum chamber, regardless of how cheap these are on Amazon

  1. Thats awesome! The last one I did used dry ice and alcohol bath to cool the plate. I never did liquid nitrogen. I really like the peltier and the bell jar with the charged element above the sample. It sure puts my peanut butter jar to shame ;)

  2. I’ve looked into this a little. A PC heat pump typically uses water vapor (under partial vacuum) as a coolant, and will bottom out at around 0 degrees, or so I’ve read. At lower temperatures the vapor will condense into ice and the heat pump no longer works.

    For better cooling, I was considering cutting into the copper pipes and replacing the coolant vapor with something else – perhaps MEC (boiling point 12 degrees) or butane (0 degrees). The freezing point of MEC is -137 degrees, so a heat pump using that as a coolant should work down to that temperature.

    Can anyone comment on this mad-scientist-like plan of mine? Does it seem reasonable?

    1. You could also use cascaded multistage peltier modules (TEC2), with proper configuration they could get down to 145 K (ref: ). A peltier device will have a lower coefficient of performance (COP) than almost all other cooling solutions, but it does have the advantage of being compact, vibration free and if a low ripple DC power supply is used low EMI. But maybe they are not suitable for your particular application which you did not mention.

    2. First thing: Are you talking about phase-change cooling or just using the working fluid to carry away heat in the liquid phase? In the latter case, how are you taking the heat out of the cooling loop? You’d probably have to use some kind of a peltier setup on the other side of the loop anyway. In that case, I’d just stick with either phase change cooling or direct peltier cooling. I don’t see the point in an intermediate liquid loop.

      If you’re talking about phase-change cooling, it makes total sense but there are technical issues to think about.

    1. You can’t be serious… No matter what radiation source you’re using (and surviving to tell about it), it isn’t going to carry enough energy to ignite the alcohol vapor.

    1. CERN generally recommends about 100V/cm so it really depends how high above the active zone is the positive electrode. I built a cloud chamber as well and in mine I am using 4.3 kV (which is an overkill as my positive mesh is 4 inches above the active zone) and it works really well! Flipping the switch of the HV increases dramatically the number of tracks and they are more defined – you can see details of my build at

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