How to Make: Cloud Chamber

In this project we will make a Cloud Chamber. The cloud chamber is a device that permits you watch the path of charged fundamental and not fundamental particles. The particles come from different sources: cosmic rays that decay into a "soup" of particles when they hit the atmosphere (see image), radiation, background radiation and other sources. This device was invented by Charles Thomson Rees Wilson and a Scottish physicist. This incredible device has been used a lot in the physics history.

P.D: This is my first instructable so any feedback will be very appreciated. English is not my maternal language. Please excuse me for errors in grammar and orthography.

For this project you'll need the following materials:
-Epoxy Glue
-Acrylic
-A sheet of metal (It isn't important which metal but it most be thin)
-Electrical tape (the black one)
-Sandpaper
-Dry ice
-A powerful lamp (I'm using a led module)
-A piece of cloth (the big of the metal sheet)
-Isopropyl Alcohol (not dissolved, 90 or higher)
-A container for the dry ice (a little bigger than the metal sheet)

Now that we have all it's time to cut it. I went to a makerspace where I cut the metal sheet into a piece of 27 by 30 cm. With an acrylic cutter I cut the acrylic into two pieces of 30 by 15 cm (this pieces will be the sides of the chamber). Then I cut two pieces more of 27 by 15 cm (this two pieces will be the back and front of the chamber). Be careful with the acrylic cutter because you can easily scratch the acrylic like I did.

You can keep the leftovers. They are excellent for other projects.

For the assembly I will use epoxy glue because its translucent and it works well with acrylic. Before pasting the last acrylic wall mount the LEDs inside and make the connections. I'm using a 2 by 3 led module which needs 12 V. If the structure isn't enough strong you can use the leftovers as support.

Be sure that there are no holes between the walls.

Now that you've finished with the acrylic lets go on with the metal sheet. You need to cover one side of the metal sheet with electrical tape so that the particle's paths are more visible. Then you need to glue with epoxy the metal sheet to the acrylic with the electrical tape facing the inside. I covered holes with more epoxy and electrical tape.

Then cut the cloth a little bit smaller than the size of the metal sheet. I used the leftovers to calculate it's big.

For the last part we'll need to cut the cover of the chamber this needs to be bigger than the camber area. What I did was glue a piece of acrylic with the same dimensions as the metal sheet only a few millimeters smaller to a bigger acrylic piece. So the chamber is completely sealed from the outside. Then I glued the cloth to the smaller piece of acrylic with some electrical tape. You can use any glue but be sure it won't be dissolved with the alcohol. See photos.

I used a very low quality glue and now my cloth is a mess so be very careful!

For finishing the chamber make. A hike near the connections of the led module so that the wires can go through the container. Then seal it with epoxy or hot glue.

Now that all is finished its time to start the setup. First of all you need to find a container for the dry ice (see photo). I'm using a biz from a table game. Then extend the dry ice in the container and lay the chamber over the dry ice. You'll see that the bottom of the chamber gets really cold. Then soak the cloth with isopropyl alcohol and resemble the chamber. You'll see like it's snowing inside the chamber. It will take around 15 minutes to cook to the desired temperature. Then you will be able to see the particles path!

P.D: I used ethyl alcohol that's why it didn't worked for me. I saw a must buy it condensed at the bottom. Be SURE you're using isopropyl alcohol!!!!

--You can skip this step if you want--

The cloud chamber works so: the alcohol evaporates in chamber. The bottom of the chamber is super cooled so that the alcohol falls down. When this is happening you see like little snowflakes falling from the cloth. This creates a super cooled alcohol mist. This mist is very unstable because the alcohol normally doesn't exists in this super cooled form.
When particles go through the mist they ionize it. This means the particles hit the alcohol atoms and remove electrons. This leaves a positive charged atom which attracts other atoms in its surrounding. As the alcohol mist is very unstable all this movement condensates the alcohol. The condensation of the alcohol is what you see and as the particle moves it condensates more and more alcohol.


Image from: http://www.cloudylabs.fr/wp/muonsphys/

If you see in your cloud chamber a straight line and the suddenly changes direction you're seeing a muon decay. A muon is a fundamental particle that travels almost at the speed of light and isn't affected by matter so it passes through almost any material. The muon decays into an electron which is the line that you see after it changed direction and into two neutrinos which can't be seen in the chamber.

The second image is a muon that hits an electron.

If you see a line with curves and/or corners you're seeing an electron.

Thick short lines are alpha particles.

Most of the particles that you'll see are muons because they are long lived. It's live is that of a microsecond or something so but thanks to the relativity of Einstein this particles have plenty of time to hit earth surface (remember, they travel almost at the speed of light).

If you don't see anything: be sure you have a enough powerful light, be sure the dry ice makes good contact with the metal sheet.


If you see a lot of mist let some escape.

If there is an air leak you'll see clouds of mist only at the edge of the chamber.

If you only see mist: remember that it take 15 minute to cool. If you don't see nothing after 15 minutes check that there is enough alcohol and that the dry ice is making good contact.

If you are having still problems write a comment and I'll answer you as quick as I can ;)


Resources:
http://web.archive.org/web/20080603025428/http://www.lns.cornell.edu/~adf4/cloud.html

https://www.physicsforums.com/threads/identifying-trails-in-a-cloud-chamber.678021/

https://en.m.wikipedia.org/wiki/Cosmic_ray

https://en.m.wikipedia.org/wiki/Muon