Your Very Own Cloud Chamber


[Kenneth] and [Jeff] spent a weekend building a cloud chamber. This is a detection device for radiation particles that are constantly bombarding the earth. It works by creating an environment of supersaturated alcohol vapor which condenses when struck by a particle travelling through the container, leaving a wispy trail behind. This was done on the cheap, using isopropyl alcohol and dry ice. They already had a beaker, and after a few tries figured out that the dry ice worked best when serving as a bed for the flask. A black piece of paper was added inside the base of the container to help raise the contrast when looking for condensate. They experimented with a couple of different methods for warming the alcohol, including an immersion heater built from power resistors.

There’s a video explaining the apparatus which we’ve embedded after the break. It’s a bit hard to see evidence of particle travel in the video but that’s all the more reason you should give this a try yourself.

28 thoughts on “Your Very Own Cloud Chamber

  1. Since isopropyl alcohol contains a ‘fair amount of water, have you tried denatured alcohol, acetone or other ‘alcohol based’ solutions as acetone or MEK (methyl ethyl ketone) to see if you are able to gather better results, instead? All those items are usually available at your local hardware store. Just a suggestion to aid in your experimentation.

  2. @M4CGYV3R: I am SO SORRY that I could not capture the particle trails for you in true HD with my crappy point-n-shoot camera. What I meant in the video is that you’ll want to turn up the resolution to 480, from the default 360. If you are so hell bent on seeing them, build one yourself.

  3. One of the simplest and most successful days of science-driven nerd-dom that Kenny and I have ever had. And it took less than three hours to get the whole thing working. Guys, don’t ever turn down the opportunity to do random things with your engineering friends. Always worthwhile


  4. my high school had an experiment-driven nuclear radiation class and we made cloud chambers. we basically took a petri dish, put a strip of velcro (the soft side) around the inside toward the top and soaked in a little nail polish remover and put our sources in the dish and put the dish on some ice. it may have been dry ice, this was a good 12 years ago, so i don’t remember that part, just that it had to be cold.

  5. @Kenneth: You’re welcome. Thank /you/ for the little mystery; I had fun solving it ;)

    For those who care (ie. nobody :P ) all I did was look up the “Mercury News” to find that it’s circulated in and around San Jose, CA (do you know the way? ;) and used the area code to do a reverse-lookup on the number. Easy as pie ;)

    (If I had read the article first, I would have seen that Kenneth’s from Sunnyvale and figured it out sooner, but I wanted to use just the photo).

  6. If you’re having trouble seeing them… set the video to 0:25 and watch to the right of the flash light. at about 0:28 you’ll see two coming streaming in right below the light, and a few inches over to the right there’s one more. Easily visible on 480p and 360p.

  7. Why wait for a random particle? Just dismantle an old ionizing smoke detector and place the bit of Americium-241 (a good alpha particle emmiter) in the beaker/petri dish. Then you’ll have a real show worthy of recording! The low energy radition from this element is blocked by as little as a single sheet of paper, so it is realatively safe. Remember to practice proper disposal after you are finished. Smoke detectors (and their batteries) are considered hazardous waste and should not be sent to the municipal landfill.

  8. Building a cloud chamber from whatever’s on hand is a great use for any dry ice you have left over from anything else.

    Tips I found on how to do that that mostly became a lot more relevant after I’d built one:

    * make sure it’s easy to see into your container. I used a mason jar that had some decorative texture and wasn’t very flat otherwise, so it was hard to see trails.

    * I used 91% isopropanol from the drugstore and it worked OK, but methanol and denatured ethanol are both supposed to be better.

    * I’m glad I bothered to use black felt in the bottom to provide contrast. The trails can be hard to see.

    * Again with contrast: lighting is critical. I used a flashlight and would be more careful setting up lighting again.

    * I just used dry ice like these guys but a dry ice and alcohol slush will provide better thermal contact with the bottom of your container.

  9. Alternatively, if you have an old antistatic brush from your film photography/darkroom days to remove dust from negatives, then there is another ready source of Alpha particles. These contain Polonium-210 mounted right behind the soft bristles.

  10. Another thing that’s wrong in the explanation: Cosmic radiation does not come from the sun. It is a feedback from the big bang, bursts created by super novae, jets of black holes and neutron stars.

    You can actually see traces in your cloud chamber at night. If they came from the sun the earth would block them at night. Earth’ magnetic field captures most particles coming form the sun, which is very good for our health.

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