Cloud Chamber

In the XX century several discoveries were made with the cloud chamber technique, including observation of anti-matter particle positron.

Modern experiments are more complex, but they share the same idea: we need a source of elementary particles for studies, and we need an apparatus to detect them and examine. We look at the simple example in our student laboratory at the Johns Hopkins University.

Particle source in our example is the radioactive isotope (rod visible inside the cloud chamber). In the decay chain, it emits alpha and beta particles.

The detector is the cloud chamber which creates a volume of super-saturated alcohol vapor that condenses on ions left in the wake of charged particles. You can see "tracks" of particles in the images below. You can also see the full movie (27 Mbyte).

See this web page for more detail and illustrations.

Andrei Gritsan
Last update: Wed Apr 26 11:49:13 EDT 2006