{"id":67004,"date":"2026-08-30T05:00:55","date_gmt":"2026-08-29T20:00:55","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=67004"},"modified":"2026-08-30T05:00:55","modified_gmt":"2026-08-29T20:00:55","slug":"see-the-invisible-tracking-alpha-rays-with-a-cloud-chamber-observing-radiation","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=67004&lang=en","title":{"rendered":"See the Invisible! Tracking Alpha Rays with a Cloud Chamber (Observing Radiation)"},"content":{"rendered":"

I’m Ken Kuwako, your Science Trainer. Every day is an experiment!<\/strong><\/p>\n

Would you like to see radiation with your own eyes in the science lab? In this lesson, we\u2019ll use a homemade cloud chamber to observe the tracks of \u03b1 particles released by uraninite, a naturally radioactive mineral.<\/p>\n

Cloud chambers are popular attractions at science museums and other educational facilities. But actually gathering the materials and building one yourself gives you a completely different feeling\u2014a real hands-on experience of doing science. For this experiment, I used a cloud chamber kit from Nuclear Engineering Co., Ltd. Although it is commercially available, it is designed to be easy to use in schools, with safety in mind.<\/p>\n

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\u3010Materials\u3011<\/strong><\/p>\n

In addition to the usual equipment found in a science lab or school, you\u2019ll need the following:<\/p>\n

\u2022 Towel (for insulation and to prevent slipping)
\n\u2022 Pad (for insulating the dry ice)
\n\u2022 Dry ice (about 1 kg, around \u00a5700)
\n\u2022 Radiation source (uraninite in this experiment)
\n\u2022 Penlight or LED light
\n\u2022 Work gloves (for protection)
\n\u2022 Anhydrous ethanol
\n\u2022 Dropper
\n\u2022 A darkroom or a room that can be darkened with blackout curtains<\/p>\n

\u203b Dry ice can be purchased from ice suppliers and similar stores. For example, near Chiba Station, there is Iwakawa Himuro.\u3000https:\/\/maps.app.goo.gl\/QMHKJdppKhRhKTXK7?g_st=ic<\/span><\/a><\/span><\/p>\n

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How a Cloud Chamber Works and What to Look For<\/span><\/h3>\n

Inside the cloud chamber, ethanol evaporates and forms a supersaturated ethanol vapor near the surface cooled by the dry ice. Because of the temperature gradient created by the dry ice, the gas inside circulates, maintaining a state in which even a tiny disturbance can cause the vapor to condense into liquid droplets. When a radiation source (uraninite) is placed inside, the tracks of \u03b1 particles appear as thin, wispy trails, much like miniature airplane contrails.<\/p>\n

\u03b1 particles can be stopped by something as thin as a sheet of paper and travel only a few centimeters. However, as they pass through the air, they create many ions. These ions act as starting points for ethanol condensation, allowing us to see the particle’s path as a visible \u201cradiation track.\u201d Shining an LED light from the side makes the white trails stand out clearly. This is usually the moment when the students go, \u201cWhoa!\u201d<\/p>\n

Uraninite as a Mineral<\/span><\/strong><\/h3>\n

The radiation source used in this experiment was uraninite. It is a mineral rich in uranium, composed mainly of uranium dioxide (UO\u2082). It belongs to the cubic crystal system, has a hardness of 5\u20136, and is exceptionally heavy, with a specific gravity of 7.5\u201310. It is also readily soluble in acids such as sulfuric and nitric acid.<\/p>\n

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\u203b Take great care when handling radioactive sources.<\/p>\n

Experimental Procedure<\/span><\/strong><\/h3>\n

1. Build the base: Place an aluminum plate on top of the dry ice and stabilize it with a towel or pad.<\/p>\n

2. Apply the ethanol: Soak a sponge or piece of felt with anhydrous ethanol and place it on the aluminum plate.<\/p>\n

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3. Position the radiation source: Attach the radiation source (uraninite) to the end of the rubber cord, insert it into the chamber, and close the lid.<\/p>\n

4. Observe in the dark: In a darkened room, shine an LED light from the side and watch for the thin trails that look like miniature airplane contrails.<\/p>\n

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