Cloud Chamber, 7D30.60

Topic and Concept:

• Cosmic Rays; nuclear decays; particle detectors

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Location:

• Cabinet: Modern Physics (MP)

• Bay: (A3)

• Shelf: 3

Abstract:

Raymaster Cloud Chamber (circa 1957)

Setup and Procedure: Half of the dry-ice-making device (wooden box) is usually connected to the CO2 cylinder. The other half is kept in the freezer.

May need to use a hammer to pound the two halves together.

CO2 cylinder must be kept upright--it's a siphon cylinder (bottom part contains liquid).

Can get 2 blocks of dry ice per CO2 tank (one right after the other); or 2 1/2 blocks if wait a week.

One block of dry ice will last for ~ 1 day.

Keep CO2 flow rate maximum that does not trip relief valve adjacent to wooden box.

Put block on top of fiberglass pan, put pan on top of styrofoam slab, and pound dry ice into powder.

Sculpt powder into "Devil's tower" shape (raised central cylinder) and place Aluminum pan on top.

Cut black paper strip and place it inside glass jar, leaving hole in glass jar unobstructed, with bottom of paper below bottom of hole.

Fill glass jar with methanol so that bottom of paper is wetted. Job of paper is to wick methanol to top, and then release methanol vapor.

Illuminate glass jar from side with bright light.

Add enough ink to the methanol so that the methanol is black.

At this point if you breathe onto the surface of the methanol, you should see condensation clouds (they look similar to the clouds one sees when breathing in the direction of liquid nitrogen).

Put on top cover.

Connect plus lead of voltage source to top cover, and minus lead to bottom cover.

Turn voltage source on.

If all is well, one should expect to see a well-defined cosmic-ray track every few seconds. Example: upper left to lower right in photo below:

There are several radioactive sources mounted on needles. Take out the black cork and insert one of these--should expect to see many tracks emanating from tip of needle.

Can also show that gamma rays go through glass by holding gamma sound outside glass tray.

Cautions, Warnings, or Safety Concerns:

• use care when controlling flow of CO2 into dry-ice-making device
• dry ice can cause frostbite
• ~100V used to clear air above methanol of ions--voltage can cause shock

Videos:

• Lecture Demonstration's Youtube Channel

References:

• List any references

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