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Forces of Nature

Lab Assignment: Cloud Chamber

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Forces of Nature Lab

Particle Physics

Goal: Detect and measure particle collisions

Materials and Procedure

  1. You will need dry ice for this experiment. This can sometimes be purchased at party supply stores in small enough quantities for this experiment. Use all recommended safety precautions in handling this material!
  2. Follow the instructions at Build A Cloud Chamber to construct your own chamber. To see how things go together with a simple setup, watch this video from CERN on making a cloud chamber.
  3. Use the chamber to detect and count types of events, events in the presence of magnets, events despite metal sheets as barriers.

    Trail types:

    • short fat straight trails are alpha particles, usually from local radioactive gasses in the soil, like radon
    • long straight trails are muons, particles produced when cosmic rays interact with atoms near the surface of the earth’s atmosphere
    • zig-zag and corkscrew trailer are electrons or positrons
    • forked trails are actual collisions
    Particle collision trails

Data Handling

  1. If possible, set up a grid behind your chamber so that you can measure length of trails. See if you can photograph any events.
  2. If you cannot photograph the events you observe, sketch several representative ones. Identify the type of trail and estimate lengths.


  1. Standard stuff: You should explain enough that someone else can repeeat your experiment to verify your results.

Post your report to the Lab thread at the Moodle.