"Neutrino" - Upward? L = up to 13000 km ?. P (? E ?? e) = 1 - sin22? Sin2 (1.27? M2L / E). 5.May 13, 2004. ??. p, He ... Second Markov Readings May 12-13, 2004 Dubna - Moscow. Oscillations of neutrinos. 2- ?. ?. Atmospheric neutrinos. S.P. Mikheev. S.P. Mikheev INR RAS. What we want to know. 3. Up / Down Symmetry. ? e.
"Methods of registration of elementary particles" - Tracks of elementary particles in a thick-layer photographic emulsion. Methods for observation and registration of elementary particles. The space between the cathode and anode is filled with a special mixture of gases. R. Emulsions. The method of thick-layer photographic emulsions. 20s L.V. Mysovsky, A.P. Zhdanov. The flash can be observed and recorded.
"Antiparticles and antimatter" - The world should have the same number of stars of every kind, "- Paul Dirac. With a constant unidirectionality of time, the ratio of matter and antimatter to the space of time, the “simplification” of Nature is different. The positron was discovered in 1932 using a Wilson camera. Refutation of Dirac's theory or refutation of the absolute symmetry of matter and antimatter.
"Methods of observation and registration of particles" - Wilson Charles Thomson Fig. The space between the cathode and anode is filled with a special mixture of gases. Piston. Registration of complex particles is difficult. Cathode. +. Wilson is an English physicist, a member of the Royal Society of London. Wilson's chamber. Counter application. Glass plate. Gas-discharge Geiger counter.
"Discovery of the proton" - The discoveries predicted by Rutherford. Silina N. A., physics teacher, secondary school № 2, p. Redkino, Tver region. determines the relative atomic mass of a chemical element. Mass and charge number of an atom. The number of neutrons in the nucleus is indicated. Discovery of the proton and neutron. Isotopes. What are isotopes? To the study of the structure of the nucleus.
"Physics of elementary particles" - In all interactions, the baryon charge is conserved. Thus, the Universe around us consists of 48 fundamental particles. Quark structure of hadrons. Chadwick discovers the neutron. Antimatter is a substance consisting of antinucleons and positrons. Fermions are particles with half-integer spin (1/2 h, 3/2 h….) For example: electron, proton, neutron.
There are 17 presentations in total
Geiger counter
Geiger counter
Geiger counter SI-8B(USSR) to measure
soft β-radiation.
Geiger counter (or Geiger-Muller counter) - gas discharge
a device for automatically counting the number of ionizing
particles.
Invented in 1908 by H. Geiger and E. Rutherford, later
improved by Geiger and W. Müller
Principle of operation
+-
R
To amplifier
Glass tube
Anode
Cathode
In a gas discharge meter
there is a cathode in the form of a cylinder
and anode in the form of a thin wire
along the axis of the cylinder. Space
between cathode and anode
filled in with a special
a mixture of gases. Between the cathode and
the anode is applied
voltage.
Counter application
The widespread use of the Geiger-Muller counter is explained by the highsensitivity, the ability to register various kinds of radiation,
relative simplicity and low cost of installation. This counter has
almost one hundred percent probability of registering a charged particle,
since one electron-ion pair is sufficient for the discharge to occur.
However, the duration of the signal from the Geiger counter is relatively long (≈
10-4 s). The Geiger counter is mainly used to register photons and
y-quanta.
Eistraikh Dmitry
Devices and installations for registration and research of particles. Diagrams of devices, their principle of operation, photographs of particle tracks.
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Presentation on physics on the topic: "Experimental methods of particle research" 9th grade student of the secondary school № 1465 Eistraikh dmitriya physics teacher: kruglova lyu.
Particle research methods: Geiger counter Scintillation counters Wilson chamber Bubble chamber Thick-layer photographic emulsions
Geiger counter
The Geiger counter is a simple device for recording radiation. It is able to detect various types of radioactive radiation (alpha, beta, gamma), but is most sensitive to γ-radiation and β-particles. The design is simple: the tube of a Geiger-Müller counter is filled with gas and has two electrodes, to which a high voltage is applied. When an ionizing particle enters the tube, a conducting channel appears between the electrodes for a while. The resulting current is detected by an electronic amplifier. Invented in 1908 by H. Geiger and E. Rutherford, later improved by Geiger and W. Muller. Geiger-Muller counters are the most common detectors (sensors) for ionizing radiation.
Connection diagram of the Geiger counter Potential difference is applied (V) between the walls and the central electrode through the resistance R, shunted by the capacitor C1. The counter is based on impact ionization. γ - quanta emitted by a radioactive isotope, falling on the walls of the counter, knock out electrons from it. Electrons, moving in a gas and colliding with gas atoms, knock out electrons from atoms and create positive ions and free electrons. The electric field between the cathode and anode accelerates electrons to energies at which impact ionization begins. An avalanche of ions arises, and the current through the counter rises sharply. In this case, a voltage pulse is formed on the resistance R, which is fed to the recording device. In order for the counter to be able to register the next particle that gets into it, the avalanche charge must be extinguished. This happens automatically. At the moment the current pulse appears, a large voltage drop occurs across the resistance R, so the voltage between the anode and cathode decreases sharply and so much that the discharge stops and the counter is ready for operation again.
SCINTILLATION COUNTERS
Schematic diagram The counter was invented by the German physicist Kalman Hartmut Paul in 1947. A scintillation counter is a device for registering nuclear radiation and elementary particles (protons, neutrons, electrons, γ-quanta, mesons, etc.), the main elements of which are a substance luminescent under the action of charged particles (scintillator), and a photomultiplier tube (PMT ).
Application of counters, their advantages and disadvantages Advantages of a scintillation counter: high efficiency of registration of various particles; high-speed performance; the ability to manufacture scintillators of various sizes and configurations; high reliability and relatively low cost. Due to these qualities, scintillation counters are widely used in nuclear physics (for example, for measuring the lifetime of excited states of nuclei, measuring the fission cross section, registering fission fragments with gas scintillation counters), physics of elementary particles and cosmic rays (for example, experimental detection of neutrinos), in industry ( γ-defectoscopy, radiation monitoring), dosimetry (measurement of γ-radiation fluxes emitted by humans and other living organisms), radiometry, geology, medicine, etc. Disadvantages of a scintillation counter: low sensitivity to low-energy particles (1 keV), low energy resolution.
Wilson chamber
The Wilson chamber (aka the fog chamber) is one of the first instruments in the history of recording traces (tracks) of charged particles. Invented by Scottish physicist Charles Wilson between 1910 and 1912. The principle of operation of the chamber uses the phenomenon of condensation of a supersaturated vapor: when any condensation centers (in particular, ions accompanying the track of a fast charged particle) appear in the medium of a supersaturated vapor, small drops of liquid are formed on them. These droplets reach significant sizes and can be photographed. The source of the investigated particles can be located either inside the chamber or outside it (in this case, the particles fly through a window transparent to them).
The principle of operation of the chamber uses the phenomenon of condensation of oversaturated vapor: when any condensation centers (in particular, ions accompanying the track of a fast charged particle) appear in the vapor medium, small drops of liquid are formed on them. These droplets reach significant sizes and can be photographed. The source of the investigated particles can be located either inside the chamber or outside it (in this case, the particles fly through a window transparent to them). To study the quantitative characteristics of particles (for example, mass and velocity), the camera is placed in a magnetic field that bends the tracks. Wilson's chamber. A container with a glass lid and a piston at the bottom is filled with saturated vapors of water, alcohol or ether. When the piston descends, due to adiabatic expansion, the vapors are cooled and become supersaturated. A charged particle passing through the chamber leaves a chain of ions on its way. The vapor condenses on ions, making the particle track visible.
General view of the Wilson chamber
Bubble chamber
Bubble chamber is a track detector of elementary charged particles, in which the track (trace) of a particle is formed by a chain of vapor bubbles along the trajectory of its motion, i.e. the detector's action is based on the boiling of a superheated liquid along the particle trajectory. Invented by A. Glaser in 1952 (Nobel Prize 1960) The principle of the bubble chamber is similar to the principle of the Wilson chamber. The latter uses the property of supersaturated vapor to condense into tiny droplets along the trajectory of charged particles. The bubble chamber uses the property of a pure superheated liquid to boil (form vapor bubbles) along the path of a charged particle. A superheated liquid is a liquid heated to a temperature greater than the boiling point for a given condition. Boiling up of such a liquid occurs when centers of vaporization, for example, ions, appear. Thus, if in the Wilson chamber a charged particle initiates the transformation of vapor into liquid on its way, then in the bubble chamber, on the contrary, the charged particle causes the transformation of liquid into vapor.
Diagram of a hydrogen bubble chamber: the chamber body is filled with liquid hydrogen (); expansion is carried out using the piston P; illumination of the chamber in the transmission is carried out by a pulsed light source L through glass windows I and a capacitor K; light scattered by bubbles is recorded using photographic lenses and on photographic films, etc.
Photo of some process of transformation of elementary particles, taken with a bubble chamber.
The method of thick-layer photographic emulsions.
To register particles, along with Wilson chambers and bubble chambers, thick-layer photographic emulsions are used. Ionizing effect of fast charged particles on a photographic plate emulsion. The photographic emulsion contains a large amount of microscopic crystals of silver bromide. The photoemulsion method was developed by Soviet physicists L.V. Mysovsky and A.P. Zhdanov in 1958. A fast charged particle, penetrating the crystal, strips electrons from individual bromine atoms. A chain of these crystals forms a latent image. When it appears in these crystals, metallic silver is reduced and a chain of silver grains forms a particle track. The length and thickness of the track can be used to estimate the energy and mass of the particle. Due to the high density of the emulsion, the tracks are very short, but they can be enlarged when photographing. The advantage of a photographic emulsion is that the exposure time can be as long as desired. This allows rare events to be recorded. It is also important that due to the high stopping power of the photographic emulsion, the number of observed interesting reactions between particles and nuclei increases.
Diagram of the method of thick-layer photographic emulsions
Tracks of particles in a thick-layer photographic emulsion.
Completed by: Andriyenko Andrey
Gomel 2015
Geiger-Muller counter - invented in 1908 by G. Geiger, and later improved by W. Müller, who implemented several types of the device .. It contains a chamber filled with gas, therefore this device is also called gas-filled detectors.
The principle of operation of the counter The counter is a gas-discharge volume with a highly non-uniform
electric field. The most commonly used meters are coaxially located cylindrical electrodes:
the outer cylinder is the cathode and a thread with a diameter of 0.1 mm stretched on its axis is the anode. The internal, or collecting, electrode (anode) is mounted on insulators. This electrode is usually made from tungsten, which produces a strong and uniform small diameter wire. The other electrode (cathode) usually forms part of the counter shell. If the walls of the tube are glass, its inner surface is covered with a conductive layer (copper, tungsten, nichrome, etc.). The electrodes are located in a hermetically sealed tank filled with any gas (helium, argon, etc.) up to a pressure of several centimeters to tens of centimeters of mercury. In order for the transfer of negative charges in the counter to be carried out by free electrons, the gases used to fill the counters must have a sufficiently low electron sticking coefficient (as a rule, these are noble gases). To register particles with a small range (α-particles, electrons), a window is made in the counter reservoir through which the particles enter the working volume.
a - end, b - cylindrical, c - needle, d - counter with a jacket, d - plane-parallel
Geiger counters are divided into non-self-extinguishing and self-extinguishing
External circuit for extinguishing the discharge.
In gas-filled meters, positive ions travel all the way to the cathode and are neutralized near it, ripping electrons out of the metal. These additional electrons can lead to the next discharge if no precautions are taken to prevent and extinguish it. The extinguishing of the discharge in the counter is caused by the inclusion of a resistance counter in the anode circuit. In the presence of such a resistance, the discharge in the counter stops when the voltage between the anode and cathode decreases due to the collection of electrons at the anode to values lower than those required to maintain the discharge. A significant disadvantage of this scheme is the low temporal resolution, of the order of 10−3 s and more.
Self-extinguishing meters.
Currently, non-self-extinguishing meters are rarely used, since good self-extinguishing meters have been developed. Obviously, in order to terminate the discharge in the counter, it is necessary to eliminate the reasons that maintain the discharge after the passage of the ionizing particle through the volume of the counter. There are two such reasons. One of them is ultraviolet radiation that occurs during the discharge process. The photons of this radiation play a double role in the discharge process. Their positive role in the self-extinguishing meter
Discharge propagation along the counter filament; negative role is the extraction of photoelectrons from the cathode, leading to the maintenance of the discharge. Another reason for the appearance of secondary electrons from the cathode is the neutralization of positive ions at the cathode. In a normally operating meter, the discharge should break off at the first avalanche. The most common way to quickly extinguish a discharge is to add another gas to the main gas that fills the meter, which is capable of extinguishing the discharge. A meter with this filling is called self-extinguishing.
Gas-discharge Geiger counter. The base of the Geiger counter is a tube filled with gas and equipped with two electrodes to which a high voltage is applied. The counter is based on impact ionization. When an elementary particle flies through the counter, it ionizes the gas, and the current through the counter increases very sharply. The voltage pulse generated in this case on the load is fed to the recording device.
Slide 5 from presentation Particle Research Methods... The size of the archive with the presentation is 956 KB.Physics grade 9
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