Cloud Chamber | Swarthmore Physics Demonstrations

The Pasco Diffusion Cloud Chamber is very easy to set up and operate- does not require use of dry ice or liquid nitrogen.
Use pump to circulate ice water through base. Peltier device cools chamber base down to -35 C.
Soak paper liner with isopropyl alcohol (93% or higher), and pour alcohol into bottom of chamber 1 mm deep.
Cloud sets up in 10-15 minutes. Cosmic ray tracks (mostly thin streaks) should readily appear.
Use radiation sources to see alpha tracks (fat streaks).
Needle source is lead 210; disk source is americium 241, extracted from a smoke detector.
Footage of this cloud chamber in operation: https://youtu.be/1ss5DBGWMo4 (sign in to YouTube to view).
Located in L01, section C1.

radioactive sources

Instructions

Soak black paper with ethanol or highly concentrated isopropyl alcohol (93% or higher).
Insert radioactive source (Pb-210) into hole on side of container.
Place chamber on slab of dry ice.
After 5 or 10 minutes of cooling down, clouds of supersaturated alcohol will form near bottom of container. Alpha particles or cosmic rays that streak through alcohol cloud ionize alcohol, causing it to condense along particle’s path.
To illuminate tracks (to make more visible) shine a flashlight, or cell phone light, into side of container.
Getting alcohol cloud to form is a little bit tricky. Before attempting this demo in class, try it out.

Located in L01, section C1.