Cloud chamber and Bubble chanber
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All of this is written by Sam Bryant based on his own project and readings so if you see somthing that looks like a mistake, it probely is.
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Introduction
The Cloud Chamber was one of the earliest forms of a particle detector. It works by supercooling alcohol molecules resulting in an alcohol cloud at the bottom of a chamber. Charged particles (cosmic rays) ionize the alcohol molecules and the positvely charged ions act as condensation nuclei for the slightly polar alcohol molecules. Light then reflects off the alcohol drops and the trails of the particles become visable to the naked eye. The cloud chamber was replaced with the slightly more advanced bubble chamber in the 50s.
History
The cloud chamber was invented in 1911 by a Scotish physicist named Charles Wilson. Wilson had been studying the effects of cloud formations and optic phenomenon in a moist enviorment. The cloud chamber was the tool used to discover the muon and the positron. The bubble chamber was invented in 1952 by Donald Glaser. Glaser received the Nobel Prize for his invention in 1960.
The Cloud Chamber
Mechanism
The cloud chamber consists of a glass tank turned upside down ontop of a supercold alcohol/dry ice solution. The alcohol/dry ice bath is placed in a cooler which is lined with a tarp. Ontop of the cooler rests a metal plate with heat sinks on the bottom to increase surface area for conduction. Ontop of the metal plate is the upside down fish tank. The top of the tank has felt pads soaked in alcohol attached to it. Due to the low boiling point of alcohol, the alcohol in the pads evaporates. The cold coming from the dry ice then causes the alcohol to condense at the bottom of the tank. It forms a small (~1cm) cloud of alcohol vapor. Charged particles then enter the chamber and ionize the alcohol molecules. Due to the slight polarity of alcohol molecules, the alcohol ions act as condensation nuclei and large droplets of alcohol vapor form in the wake of the particles.
Trails
Many differnt particles trails can be observed withen the chamber. The most basic path is a single, skinny, white line and they occur quite frequently. These paths are either electrons, positrons, muons, anti-muons, or a few other possibilities. Sometimes a spiral is observed in the chamber. This is caused by a low energy Beta particle (electron, muon, anti-muon, etc.) interacting with molecules. Because it is low energy it is more suceptable to interacting with forces withen the chamber. The spiral is caused by it bouncing off of molecules.
Another path that can be observed is a v-shaped trail. This is a bit more complicated. It is either electron-positron annihilation, or electron-positron creation.
Annihilation is caused by a particle and its anti-particle colliding. In this case an electron collides with a positron (equal masses but oppisite charge) and their energy is converted into two virtual photons (photons allowed to have small mass due to uncertainty).
Creation, the more likely candidate of the two, is the oppisite. It is when a high energy photon collides with another photons and it results in the creation of an electron and a positron.
The diagrams above are called Feynman diagrams and notate the actions of subatomic particles over time. Backwards arrows represent anti-particles because of the fact that anti-particles are particles moving backwards in time theorized by Feynman's correction of Dirac's Equation.
Annother possible picture is a Y-shaped trail. This is when a high energy beta particle hits an electron in a molecule and knocks it out of orbit. The branch of the Y is the two negatively charged particles ionizing the alcohol. When a line suddenly kinks off in one direction it is muon decay. The difference between the Annihilation/Creation track and the muon decay track is that the muon decay will be much closer to a straight line whereas the annihilation/creation trails look like Vs.
Current Projects
Cloud chamber's experimental usage has long been extinct. Cloud chambers are now primarily used for classroom demonstrations because they are cheap and very effective. Samuel Bryant is currently working under Helio Takai to develop an electrically cooled cloud chamber pratical enough for classroom use.
Measuring Energy
Here's an idea for determining the energy of diiferent particles using a cloud chamber. Setup a cloud chamber (or a bubble chamber) with a grid marked on the metal plate. Have a magnet placed along the length of one of the sides of the chamber. Based upon the magnetic field's power over particle direction then the energy of the particle can be detected. This would only work if you knew the type of particle which is determinable in a cloud chamber based on what the trail looks like. One potential problem is that if any of the measurments are slighty off then due to the exponential nature of many of the equations, the whole answer would be off
The Bubble Chamber
Mechanism
A container is filled with a superheated liquid. As charged particles come in a trail of ionization causes the liquid to vaporize along the trail of the particle. This leaves a trail of bubbles in the wake of charged particles.
