Cloud chambers work by creating a supersaturated vapor in a chamber. Particles that pass through ionize the air, causing the vapor to condense along the track, forming "rain". An external magnetic field (even that of the earth) cause the particles to curve.
There are two basic flavors:
Bizarre Stuff - Cloud Chamber: http://freeweb.pdq.net/headstrong/Cloud.htm (nice simple diagrams for both types)
Andy Foland's Cloud Chamber Links Page http://www.lns.cornell.edu/~adf4/cloud_bib.html (lots of links to other sites some of which have construction details, etc.(of course, some of the links are "dead", such being the ephemeral nature of the web)
Joseph Zambelli - Construction and Operation of a One Atmosphere Diffusion Cloud Chamber http://www.students.bucknell.edu/zambelli/cchamber/ This is a nice unit based on a surplus freezer which cools to around -10C, and resistance heaters to heat the working fluid. (note new URL, 3 Nov 2000)
cloud.htm - revised 3 November 2000, Jim
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