Wilson cloud chamber

Wilson cloud chamberWilson cloud chamber was the first device capable of registering traces of charged particles. In other words it is a track detector.It was invented at the beginning of the last century by Charles Wilson, a Scottish engineer who consequently received a Nobel prise for this invention.The chamber consists of a tank that has a glass lid on one side and a piston on the other. The tank is filled with vapours of water, alcohol, ether or the mixture of the three. When the piston strikes the vapour inside expands and consequently cools down. The vapour becomes oversaturated. When a charged particle flies through the chamber it leaves an ion track. Vapour condensates on the ions. Thus the track becomes visible as a track condensate. These drops can be easily seen and photographed.The value of oversaturation, necessary to produce drops on ions, depends on the quality of vapour as well as on the value of the charge. Water vapours mostly condensate on negative ions, while ethyl alcohol vapours condensate on the negative ones.The source of charged particles can be situated either inside or outside the chamber. In order to measure the momentum of particles the chamber is placed inside an external magnetic field. The tracks of the particles bend. Later, judging by their photographs one can determine the speed and mass of a registered particle.Although the device is very simple, Wilson chamber was an important invention of its time. With its help scientists carried out many tests with nuclear radiation. It led to a number of discoveries in cosmic-ray, muon, and positron physics. Wilson chamber was an important step towards the development of modern charged particle detectors.

Category:

Science & Technology

[Vfried]

yOU SAID: "Water vapours mostly condensate on negative ions, while ethyl alcohol vapours condensate on the negative ones." There appears to be attention drawn to a difference, but where is the difference? Does water condense on the positive? Thanks