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What is a cloud chamber?
What is a cloud chamber?
The loan kit contains a diffusion cloud chamber that does not require any dry ice. A cloud chamber is a good way to show up the radiation produced by radioactive sources, as well as the radiation present in our environment, known as background radiation.
The cloud chamber was invented by Charles Thomson Rees Wilson. He used his understanding of how clouds in the air are formed, from water vapour condensing onto ions, to create a device that allows us to see the tracks of subatomic particles, smaller than an ion, with our bare eyes.
You can find out about the history of the cloud chamber, and how they can be used to detect radiation, in the video below by Alexander Backis, a post-graduate researcher at the University of Glasgow.
How It Works
How It Works
At the bottom of the chamber is a metal plate cooled by circulating ice water through the base and further cooling it to -35°C. You can see a thin film of liquid alcohol on top of it. At the top of the chamber is a glass plate with fine heating wires. Alcohol is evaporated from this plate at a temperature of about 50°C. The isopropyl alcohol placed in the chamber wicks up the inside chamber lining, where it evaporates in the warmer region of the chamber and diffuses downward. The alcohol vapour is then cooled near the chamber bottom, becoming super saturated.
As energetic alpha and beta particles from a radioactive source pass through the alcohol vapour, the vapour condenses, forming droplets that appear as tracks in the strong chamber cross-lighting - the small droplets of alcohol show where the particle has passed through. It’s a bit like the vapour trails you see when a jet aircraft flies through the high, cold atmosphere.
Setting up the cloud chamber
Setting up the cloud chamber
What you need
What you need
Before you set up the cloud chamber, please note that there are two substances required for its use that are not provided in the loan kit:
Propan-2-ol (30 ml);
Water ice (2 kg).
(The quantities in brackets are the required amounts for each time the cloud chamber is set up and used).
We also do not provide you with a radioactive source. A source for use with the Diffusion Cloud Chamber is Pb-210, (which you can buy if you have the requisite safety certificates). However, the cloud chamber can still be used without a radioactive source, as you can pick up the tracks of cosmic rays. An example alternative for a source you may have in your school is a thorium welding rod.
In the cloud chamber box itself, you will find the main device, the power cable, and the components of the pump, (the pump and the rubber tubes).
In the small blue box, (which itself is used for the ice bath) you will find the equipment for handling the propan-2-ol, (measuring cylinder and beaker, safety glasses, and pipette) as well as the masking tape to hold the tubes in place.
How to set it up
How to set it up
You can find out how to set up the cloud chamber, and what to look for once the cloud chamber is up and running, in the video below by Kayleigh Gates, a nuclear researcher from the University of Glasgow. Please watch this video through before setting up your cloud chamber, so that you are aware of the safety measures, as well as reducing the likelihood of causing damage.
In the cloud chamber box is also the Manufacturer's instruction manual that you can refer to for more details about the cloud chamber's operation. Just a few notes in addition to Kayleigh's video above:
Due to the packing of the cloud chamber, the rubber hoses aren't sent connected to one end of the cloud chamber device, so please attach these when you are setting it up.
As Kayleigh mentions in the video, the pump of the cloud chamber has a black stopper on one end of it. Please check this is in place when you pack the cloud chamber away.
The additional components you need for the cloud chamber operation, in addition to what is in the box itself, are found in the small blue box. The blue box itself is to be used as the ice bath to submerge the pump in, (fill it about halfway with cold water).
If you have any questions about setting up the cloud chamber, please feel free to contact us at physics-bindingblocks@york.ac.uk.
Teaching Material
Teaching Material
Pre-16 Masterclass
Pre-16 Masterclass
Module 2: Properties of Radiation
Many substances are radioactive – they give out particles which travel through the air until they are absorbed, either by the air itself or by some other material that blocks their path. Looking into a cloud chamber, you see the tracks of electrically charged particles as they pass through the chamber. If there are no radioactive sources nearby, we can still see tracks from cosmic rays, which can have effects on our technology on Earth. You can tell from the irregular particle tracks that they lose energy as they interact with air molecules. The straightest tracks are from the fastest, most energetic particles.
Class Worksheets
Class Worksheets
When using the cloud chamber with your classes, you may wish to use the worksheets below for the students to check their understanding about the different types of radiation that can cause these tracks. There is a student document, and an accompanying teacher document:
Isaac Physics Questions
Isaac Physics Questions
You can find some Isaac Physics questions you can set to your students related to radiation. Please feel free to look at our page for help setting up an account on Isaac Physics!
Pre-16 Level
Post-16 Level
Note: the "Properties of Radiation" questions use the radiation and matter interaction simulation.
Buy or build your own
Buy or build your own
Where to buy your own
Where to buy your own
The cloud chamber included in the loan kit is a PASCO diffusion cloud chamber, with the accompanying Pb-210 source. This was delivered to us by VITTA education. Please note, however, that the pump provided in the loan kit comes with an American/Swiss-style plug and an adapter to the UK 3-pin plug. For safety, you may want to have the plug itself altered rather than using an adapter. For more information, please get in touch with us!
How to build your own
How to build your own
Dr Steve Barrett at the University of Liverpool has designed his own cloud chamber that you can easily and cheaply build yourself. Learn more about how he's done this and how you can also build your own.
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