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Cloud Chamber (Classroom Size) (V 6)

Keyword: Atomic Physics

Demonstration Description:

V 6: (New) Classroom Demo

TSG must have at least 1 day notice. Assume a minimum of 1 hour for set up, viewing of cosmic rays.

Chamber and cover must be clean (no dust, fingerprints, etc.) Add alcohol to saturate felt liner of chamber; use pipette to ‘hurry’ things if needed. Need 2 mm alcohol on bottom after felt is saturated. Pump must be submerged in ice water. Large pump generates a lot of heat; fill 16 quart cooler with ice, then add water.
If you need it to run for more than 2 hours a larger cooler is needed.

Free hose end (a.k.a., water return tube) returns water to ice chest; place in ice water. Check water return tube frequently during operation to verify water flow. Plug into AC outlet so that the cord drapes (water drips to floor rather than into outlet). It takes time for saturation to develop, a minimum of 30 minutes.

Once saturation occurs tracks from cosmic rays (or from Pb 210 source) will be visible.

V 6: (Old) Special Events (Large Crowds)

Concentrated rubbing alcohol is poured into a glass box that sits on a bed of dry ice. This cools the alcohol to the point of supersaturation. When a high energy particle passes above the supersaturated layer it ionizes the air, causing the alcohol vapor to condense and leave a visible trail. The tracks from subatomic particles such as cosmic ray muons, alpha particles, and high energy electrons can be seen. A Thorium decay source (piece of welding rod) can be inserted into the box to show alpha decay, and a magnet placed under the box will cause electrons to curve.