Cloud Chamber
A cloud chamber is a type of device for visualizing the tracks of radiation. The paths of radiation are made visible by cooling a vapor of isopropyl (or other) alcohol to supersaturation. When high energy particles (or photons, etc) pass through the region of supersaturated vapor they trigger the phase transition from vapor to droplet form. The tiny droplets which condense in the path of the radiation then scatter light to the eyes of the watcher. This is seen as the formation of thin streaks of 'clouds'.
Assembly notes
Two thermoelectric coolers off ebay from China: 12709 and 12710 (<$10 each). "127" stands for the number of thermoelectric pillars. "09" and "10" stand for 9 and 10 amps respectively. Rosewill RCX-ZAIO-92 CPU Cooler ($20) from newegg. PC PSU with sense pin shorted to ground with a signal diode's voltage drop; 12v used for the cooler fan and bottom thermoelectric cooler (12710). 5v for the top cooler (12709). I used artic silver ceramic heat compound for the thermoelectric stack and ceramic + silver mixed for coupling to the plasic container ($10).
While conduction through the plastic does produce a decent fog I think it best to cut a square hole for the cooler stack and cover it with a nonconductive thin film of some kind like kapton. The kapton tape would also seal the hole in the plastic so condensed alcohol and black dye does not drip down onto the thermoelectric coolers (video, applying kapton tape without bubbles, 3 inch 1 mil, $22). Alternately, a foil tape like aluminum or copper tape can be tried; but they might conduct heat too well.
The plastic might be a little bit thick, but I'm getting plenty of fog. I just need to add the LED light bar and electrostatic clearing for ions now. For the former I'll just buy a strip off ebay, for the later I'll use an old mains powered CW multipler I made that runs about 600v when not loaded. If that doesn't work I'll use a neon sign transformer.
I don't have the magnets yet, but I bought that Rosewill heatsink specifically because it had a large clear space for placing a strong 2"x2"x1" N42 or greater neodymium magnet below the coolers in the space between the heatpipes and heatsink. A second magnet of the same size will be placed on the top of the chamber. This should give a field of ~2 tesla directly above the thermoelectric coolers. Electrons and other light ions with noticibly bend.
Inspiration and most credit should go to Rich Olson and Samuel Fonteneau.
