Cloud Chamber Subatomic Cosmic Ray Particle Detector
A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.
Materials Needed
- • Clear straight-sided glass jar with flat metal lid (1 unit)
- • Black felt fabric circle (1 piece)
- • 99% (or 91%) Isopropyl alcohol (1/4 cup)
- • Dry ice block or dry ice pellets (handled by adult) (1 small block)
- • High-intensity LED pocket flashlight (1 unit)
- • Heavy insulated leather work gloves (1 pair)
Pro Tips
- → Glue black felt inside the bottom of a glass jar and saturate it with 99% isopropyl alcohol.
- → Place the metal lid flat onto a block of dry ice and set the jar upside down on top of it.
- → The extreme cold below creates a layer of supersaturated alcohol vapor near the metal base; ionizing cosmic rays trigger vapor condensation, creating visible white vapor trails.
Safety First
Adult handles dry ice strictly with heavy insulated work gloves to prevent cold burns. Do not inhale vapor in unventilated spaces.
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Step-by-Step Instructions
Step 1
Glue a disc of black felt to the inside bottom of a glass jar and saturate the felt with 99% isopropyl alcohol.
Step 2
Set the jar upside-down on its flat metal lid resting directly over a flat slab of dry ice, ensuring an airtight seal.
Step 3
Allow the chamber to cool for 10 minutes until a gentle mist forms above the black metal base, indicating supersaturation.
Step 4
Shine a bright horizontal LED beam across the base in a dark room to observe sharp, whispy condensation trails left by natural cosmic rays.