Cloud chamber

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A Cloud Chamber , also known as Wilson Cloud Chamber , is a particle detector used to visualize ionizing radiation paths.

Cloud space consists of a closed environment containing moisture or alcohol is saturated. Energetic charged particles (eg, alpha or beta particles) interact with the gas mixture by tapping the electrons from the gas molecules through the electrostatic force during a collision, generating traces of ionized gas particles. The resulting ion acts as a condensing center in which a small droplet trace is formed when the gas mixture is at the condensation point. This droplet is seen as a "cloud" track that lasts for a few seconds while drops fall through the steam. This track has a distinctive shape. For example, an alpha particle track is thick and straight, while the electron path is very thin and shows more deflection evidence due to a collision.

Cloud spaces played an important role in experimental particle physics from the 1920s through the 1950s, until the emergence of bubble spaces. In particular, the discovery of positrons in 1932 (see Fig.1) and muons in 1936, both by Carl Anderson (awarded the Nobel Prize in Physics in 1936), used the cloud chambers. Discovery kaon by George Rochester and Clifford Charles Butler in 1947, also made use of cloud space as a detector.. In any case, cosmic rays are the source of ionizing radiation.

Video Cloud chamber

Discovery

Charles Thomson Rees Wilson (1869-1959), a Scottish physicist, is credited with creating a cloud space. Inspired by the appearance of the Brocken ghost while working at the top of Ben Nevis in 1894, he began to develop an expansion chamber to study the formation of clouds and optical phenomena in the humid air. Very quickly he found that the ions can act as the center of the formation of water droplets in such rooms. He pursued the application of this discovery and refined the first cloud space in 1911. In the original room of Wilson the air inside the sealed device was saturated with water vapor, then the diaphragm was used to expand the air indoors (adiabatic expansion), cooling the air and beginning to condense water vapor. Hence the name cloud space expansion is used. When ion particles pass through space, moisture condenses on the resulting ions and traces of particles are seen in the vapor clouds. Wilson, along with Arthur Compton, received the Nobel Prize in Physics in 1927 for his work in the cloud room. Such a space is also called pulsed chamber because the conditions for the operation are not maintained. Further developments were made by Patrick Blackett, who used a stiff spring to expand and squeeze space very quickly, making the room sensitive to particles several times per second. Cine film is used to record images.

The diffusion of cloud chamber was developed in 1936 by Alexander Langsdorf. This space differs from the expansive expanse of cloud space continuously sensitized to radiation, and below it must be cooled to a rather low temperature, generally cooler than -26 Â ° C (-15 Â ° F). Instead of water vapor, alcohol is used because the freezing point is lower. Cloudy spaces cooled by dry ice or thermoelectric cooling peltier effect are common demonstration devices and hobbies; Alcohol used in it is usually isopropyl alcohol or alcohol.

Maps Cloud chamber

Structure and operation

Type-diffusion cloud spaces will be discussed here. A simple cloud space consists of a closed environment, a warm top plate and a cold bottom plate (See Figure 2). It requires a source of liquid alcohol on the warm side of the room where the liquid evaporates, forming a steam that cools as it falls through the gas and condenses in the cold bottom plate. A kind of ionizing radiation is needed.

Methanol, isopropanol, or other alcoholic vapors fill the space. Alcohol falls when cold and cold condenser provides a steep temperature gradient. The result is an environment that is not saturated. As the energetic charged particles pass through the gas they leave an ionization trace. The alcohol vapor condenses around the ion gas traces left by ionizing particles. This happens because the molecules of alcohol and water are polar, resulting in a net appeal to the nearest free charge. The result is a formation like a misty cloud, judging by the drops falling into the condenser. When a track is radiated radially from a source, their original point can be determined easily. (See Figure 3, for example.)

Right above the cold condenser plate there is a volume of space that is sensitive to ionization tracks. Traces of ions left behind by radioactive particles provide the optimum trigger for condensation and cloud formation. This sensitive volume increases with a steep temperature gradient, and stable conditions. Powerful electric fields are often used to draw cloud tracks into the sensitive areas of space and increase the sensitivity of the room. The electric field can also function to prevent a large number of "rain" background from obscuring the sensitive area of ​​space, caused by the formation of condensation above the sensitive volume of the chamber, thus obscuring the track with constant precipitation. The black background makes it easier to observe the cloud tracks. Normally, a tangential light source is required. It illuminates white droplets with a black background. Often the track is not visible until a shallow alcohol pool is formed in the condenser plate.

If a magnetic field is applied across the cloud space, the positively charged and negative particles will bend in the opposite direction, according to the law of Lorentz forces; However, the areas that are quite powerful are difficult to achieve, but with a small hobby setup.

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Other particle detectors

The bubble room was created by Donald A. Glaser of the United States in 1952, and for this, he was awarded the Nobel Prize in Physics in 1960. Space bubbles also revealed traces of subatomic particles, but as traces of bubbles in superheated liquids, usually liquid hydrogen. Bubble spaces can be made physically larger than the cloud space, and since they are filled with a much denser liquid material, they reveal traces of more energetic particles. These factors quickly made the bubble space of the dominant particle detector for decades, so the cloud space was effectively replaced in fundamental research in the early 1960s.

Spark space is an electrical device that uses an uninsulated electrical wire grid in a room, with a high voltage applied between cables. The energetic charged particles cause the ionization of gases along the particle path in the same way as in Wilson's cloud chamber, but in this case the ambient electric field is high enough to accelerate full-scale gas damage in the form of sparks in the initial ionization position. The presence and location of this spark are then electrically registered, and the information is stored for later analysis, such as by digital computers.

Similar condensation effects can be observed as Wilson clouds, also called condensation clouds, in large explosions in moist air and other Prandtl-Glauert singularities.

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See also

• Nuclear emulsion - also used to record and investigate charged particles
• Bubble Room
• Space spark plug
• Gilbert U-238 Atomic Energy Science Laboratory for children (1950-1951)
• Contrail

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Note

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References

• Das Gupta, N. N; Ghosh S. K. (1946). "Report on Wilson Cloud Space and Applications in Physics". Modern Physics Reviews . 18 (2): 225-365. Code Bib: 1946RvMP... 18..225G. doi: 10.1103/RevModPhys.18.225.

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External links

• YouTube: "A Cloud Chamber Diffusion"
• Many images of nuclear interaction and experience
• Cloud space videos with radioactive sources
• Cloud demonstration video room, Peter Wothers, Royal Institution, December 2012
• "Cloud Chambers". Archived from original on June 30, 2008.
• Diffusion cloud spaces
• "Cloud space used in physics teaching"

Source of the article : Wikipedia