Diffusion Cloud Chamber - large

7D30.60 | Ad4
PS H156
  • demonstration image
    Cloud chamber and light source with room lights on. Vapor cloud is visible at the bottom of the chamber. The white on the bottom of the exterior sides is frost on the elastic draft screen used to extend the life of the dry ice under the chamber
  • demonstration image
    Cloud chamber and light source with room lights off. Vapor cloud becomes more visible.
  • Particle tracks constantly appear and disappear in the vapor cloud.
    Particle tracks constantly appear and disappear in the vapor cloud. Most events observed are cosmic rays. Decays of airborne radionuclides can also be observed. Alpha particles from such decays produce short dense tracks in the chamber. ASU
  • demonstration image
    More particle tracks are seen looking down into the vapor cloud.
Uses 95% ethanol, keep ignition sources away, keep slide projector 18 away minimum. Use caution in handling dry ice. Do not use ethanol twice for this demo but save the leftover for use in the elementary labs. Any disposal must be as hazardous waste.
Date Added: 
Friday, March 1, 2002 - 12:00am

Supersaturated Environments Lecture hall Cloud Chamber


Preparation must allow 30 minutes to establish thermal equilibrium. Use 95% ethanol from Lab Stores - they buy it by the drum and will fill our container. A form must be signed by an authorized signer(Tim). Each use requires 500ml. Use about half of it to saturate the felt around the top of the enclosure and pour the rest on the chamber bottom to provide a uniform, low glare surface. Replace the glass top and be sure it rest flatly in its place. Clean the outside glass top with antifogging solution. The alcohol must be added and the top treated before cooling the chamber. Choose dry ice slabs that are the same thickness so the chamber bottom will be level and in contact with all the dry ice. This takes a little selection. So far we are using 6 slabs but we may be able to get by with 4. Distribute the dry ice on the foam base of the chamber leaving at least 1 to the edge of the foam. Stretch the elastic skirt around the corner supports to reduce dry ice consumption and place the chamber on the dry ice. Level the chamber. The chamber may be ready in as little as 15 minutes but allow 30. It will continue operation for up to 8 hours. With room lights darkened shine the slide projector through the thick Plexiglas on the partially masked side. This gives good light at the active volume of the chamber(near the bottom) while shielding the eyes of the observer. The slide projector must be kept at least 18" from the chamber wall. Don�t open up the chamber during use, it might ruin the cloud for a time. After use, the alcohol is drained back into the bottle and dyed blue with food coloring and kept for miscellaneous cleaning. After use, the dry ice is discarded and the whole thing set to air dry overnight with the chamber elevated on blocks for air circulation underneath. Make sure it is set to air dry over night, if left wet overnight there may be damage to the finish, etc.

There is no better way to give students a realistic feeling for the "facts of radiation" - that we're all constantly exposed to background radiation.

Cloud Chamber, Elastic Skirt, Dry Ice, Slide projector, 95% ethanol, antifog compound

Great for Open House nights, costs some money to run for the dry ice, the public really likes this one
Equipment Information: 
Do not leave overnight without disassembling and drying out to avoid water damage from condensation, etc.