Unveiling the invisible
Radioactivity interferes with matter by ionising atoms. It doesn't make the atom radioactive (excepted in nuclear reactors and bombs when there occurs an emission of neutrons) but it extracts electrons from their electronic shells. The supersaturated alcohol vapor condenses next to those ions (atoms with a gain or a deficit of electrons) leaving a trail on the path of the particle.
In a cloud chamber, you can see the trajectory of charged particles from radioactive decays or cosmic rays. One can use a magnetic field in order to estimate the charge, mass or energy of the particles.
Design of my cloud chamber
While the majority of Cloud chamber is cooled with dry-ice (solid CO2) which is not easily available and a consumable material, this design is cooled electrically thanks to Peltier elements. It uses 4 Peltiers stacked 2 by 2, the upper one is powered in 5V DC current and the lower one 12V which results in a 8x4cm interacting surface maintained at -30°C for a total power consumption of 330W.
The principle of the Peltier cloud chamber comes from this tutorial : Make a cloud chamber using peltier cooler
The design is widely inspired by this particular cloud chamber : Cloud chamber blog
Another good looking and efficient design : Cloud chamber Flickr
Here is a step by step video of the construction of my cloud chamber :
youtube video
In my apparatus the magnetic field is created by 2 powerful NdFeB magnets (grade N42, 40x40x20mm) and directed vertically toward the bottom of the chamber.
The HV wire inside the chamber helps clearing residual ions. The LED and black plastic allow visualizing the tiny tracks of condensation with enough contrast.
My goal was to make the most compact design so it can be easily transported. It’s almost “plug and play” but you still have to soak the sponge material with isopropyl alcohol. Then you turn on the main switches on the PC power supply, the first condensation trails appears about 10 seconds after. You can use the 2 switch to turn ON/OFF the LED lights and the HV wire.
Although the apparatus is simple to use, great care must be taken when handling the 2 magnets, they are very dangerous and must never be moved close to each other (with around 60kg of holding strength they could break fingers or crack and send sharp splinters into eyes) .
