1. The Cloud Chamber Bengu Bozlar*
* MEB Istanbul Science and Art Center-Istanbul,Turkey –
Introduction
Procedures
Results
Conclusion
Cloud chamber was used to detect cosmic particles in 1900s. It is a chamber which filled up supersaturated alcohol vapour. Charged cosmic particles pass through in the chamber and leave alcohol droplet tracks behind by ionizing. All varied particles make different tracks because of their energy. Charles Thomson Rees Wilson invented the first cloud chamber in 1911 and was awarded the 1927 Nobel Prize for Physics, jointly with Arthur Holly Compton. Positron, muon and kaon were discovered by means of cloud chamber. The technique open the doors of particle detector technology and provided the first way of imaging charged particles released by X-rays, in radioactive decays and in nuclear interactions.
To build up cloud chamber, needs of materials are;
·         dry ice (solid carbon dioxide),
·         isopropyl alcohol 99%,
·         felt,
·         split pins,
·         a very intense flashlight,
·         black metal plate,
·         box for dry ice,
·         clear plastic container for covering completely black metal plate,
·         safety goggles, nitrile protection gloves for isopropyl alcohol, leather protection gloves for dry ice.
Figure 1. Final setting of cloud chamber. From ̋Cloud Chamber Do-it-yourself manual,̏ by Woithe J.,2016,S-cool LAB.
After cloud chamber is settled down, it will be waited for 5-10 minutes to get everything cooling down and reaching heat balance. In completely dark room, only flash lights should illumine inside the chamber. Cosmic particles tracks will be seen arising inside chamber.
Considering shape, thickness and action of particles, thin straight particles are high energy muons, electrons or their corresponding anti-particles. Muons have a mass of 200 times more than an electron, which makes them keep path directions sustained than electron if impacted by other particles.
Curly tracks are appeared by slow electrons or photoelectrons which have low energy and scatter easily.
Thick straight particles are alpha particles. They lose their energy quickly that makes tracks short.
Forked tracks are muons transforming into electron and two neutrinos.
Figure 2. Tracks of charged particles
Pupils have deeper understanding of natural radiation and cosmic particles those they don’t see in daily life by cloud chamber. They have retention of content knowledge of subatomic world and engage to provide real world relevance with it. Collecting data of cloud chamber and interpret them according to outer view contribute to promote analytical thinking skills of them. Meanwhile,It encourages scientific occasions in the classroom.
Bibliography
Longair,M. (2014). C.T.R. Wilson and the cloud chamber. Astroparticle Physics, 53, 55–60.
Woithe,J. (2016). Cloud Chamber Do-it-yourself manual.S’cool LAB.