Using a Lascells Cloud Chamber to See the Radiation Around Us – With a Balloon

 

Using a Lascells Cloud Chamber to See the Radiation Around Us – With a Balloon

Radiation is all around us, but it’s invisible to the naked eye. To make it visible, we use a Lascells Cloud Chamber, a simple yet powerful device that shows the tracks left by charged particles as they pass through supercooled alcohol vapour. With the addition of something as ordinary as a balloon, we can turn a classroom demonstration into an unforgettable visual experiment.

How the Cloud Chamber Works

A cloud chamber creates a layer of supersaturated alcohol vapour above a cold metal base. When alpha or beta particles travel through this layer, they ionise the vapour, leaving behind fine condensation trails—like miniature vapour trails from aircraft. These tracks reveal the otherwise invisible world of background radiation.

Adding the Balloon

To increase the number of visible tracks, we can bring in a simple tool: a balloon.

• Inflate and rub the balloon to create static electricity.

• Stick it to the wall and leave for a while

• The balloon will attract ionised particles.

• Deflate and place in the cloud chamber.

• The static charge helps attract particles and enhances ionisation near the surface, producing a burst of new tracks.

It’s a safe and engaging way to demonstrate that radiation is a natural part of our environment and that even small changes in surroundings can affect what we observe.

What Students Learn

• Radiation is constantly present in the environment.

• Alpha and beta particles leave distinct tracks—thick, straight lines or thin, wavy paths.

• Electric fields can influence how these particles behave.

The Takeaway

Using a Lascells Cloud Chamber brings nuclear physics out of the abstract and into view. Adding a balloon makes the invisible visible—helping students connect the physics of radiation to the world they live in.

Here’s a list of easily available, low-level, naturally occurring radiation sources that are safe to handle and perfectly suitable for cloud chambers or Geiger-counter experiments. None of these require a licence or involve hazardous materials.

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Safe, Readily Available Radiation Sources

1. Everyday Air (Radon Daughters)

• What it is: Air always contains tiny amounts of radon gas and its decay products.

• What you’ll see: Even with no deliberate source, a cloud chamber will show a few background alpha and beta tracks every minute.

• Tip: Leave the chamber running for 10–15 minutes to allow natural particles to drift in.

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2. Granite and Stone

• What it is: Many rocks, especially granite, contain trace uranium and thorium.

• Use: A small piece of polished granite or a kitchen worktop sample placed near a detector often increases the count slightly.

• Safety: Safe to handle; levels are extremely low.

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3. Potassium-Rich Substances

• What it is: Potassium-40 is a naturally radioactive isotope.

• Where to find it:

  • Bananas

  • Dried beans and nuts

  • Fertiliser containing potassium chloride (potash)

• Observation: You might detect a slight increase in background radiation with a sensitive counter—barely above normal but measurable.

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4. Smoke Alarms (Ionisation Type)

• What it is: Some older smoke alarms use a tiny, sealed americium-241 source (alpha emitter).

• Use: Place the entire sealed alarm near your detector—never dismantle it. The casing is designed for safety, and emissions are extremely weak.

• Safety: Do not open or damage the alarm. Keep it intact.

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5. Ceramic Glazes and Glass

• What it is: Some older orange or red ceramics (especially “Fiesta ware”) and certain vintage camera lenses contain trace uranium oxide in the glaze or glass.

• Use: Safe to handle, interesting for comparison if available second-hand.

• Note: Not recommended for children—keep as demonstration curiosities only.

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Background Radiation Itself

Even without deliberate sources, your detectors will always show some radiation. Cosmic rays, terrestrial isotopes, and even materials in building walls provide a gentle, constant background.

Use this as a teaching point: radiation is a natural part of the environment.

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Summary Table

Source Type	Example	Type of Radiation	Safety Notes
Air (radon daughters)	Ambient	Alpha/Beta	Background only
Rocks	Granite, slate	Gamma	Safe to handle
Potassium-40	Bananas, fertiliser	Beta/Gamma	Very low level
Smoke alarm (sealed)	Americium-241	Alpha	Never dismantle
Vintage ceramics/glass	Uranium glaze/lens	Beta/Gamma	Handle only briefly

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Teaching Point

Using natural and everyday items shows students that radiation is not exotic or inherently dangerous—it’s simply part of our environment, detectable with the right instruments and respect for safety.