1.
Magnetic lens
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A magnetic lens is a device for the focusing or deflection of moving charged particles, such as electrons or ions, by use of the magnetic Lorentz force. Its strength can often be varied by usage of electromagnets, magnetic lenses are used in diverse applications, from cathode ray tubes over electron microscopy to particle accelerators. From this configuration a customized magnetic field can be formed to manipulate the particle beam. The passing particle is subjected to two vector forces H Z, and H R. H R causes the particle to spiral through the lens, and this spiraling expose the electron to H Z which in turn focus the electron. Note that the field is inhomogeneous, particles close to the center are less strongly deflected than those passing the lens far from the axis
2.
Electrostatic lens
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An electrostatic lens is a device that assists in the transport of charged particles. For instance, it can guide electrons emitted from a sample to an electron analyzer, systems of electrostatic lenses can be designed in the same way as optical lenses, so electrostatic lenses easily magnify or converge the electron trajectories. An electrostatic lens can also be used to focus an ion beam, a cylinder lens consists of several cylinders whose sides are thin walls. Each cylinder lines up parallel to the axis into which electrons enter. There are small gaps put between the cylinders, when each cylinder has a different voltage, the gap between the cylinders works as a lens. The magnification is able to be changed by choosing different voltage combinations, although the magnification of two cylinder lenses can be changed, the focal point is also changed by this operation. Three cylinder lenses achieve the change of the magnification while holding the object, although the voltages have to change depending on the electron kinetic energy, the voltage ratio is kept constant when the optical parameters are not changed. While a charged particle is in a field force acts upon it. The faster the particle the smaller the accumulated impulse, for a collimated beam the focal length is given as the initial impulse divided by the accumulated impulse by the lens. This makes the focal length of a lens a function of the second order of the speed of the charged particle. Single lenses as known from photonics are not easily available for electrons, the cylinder lens consists of defocusing lens, a focusing lens and a second defocusing lens, with the sum of their refractive powers being zero. This indirectness leads to the fact that the refractive power is the square of the refractive power of a single lens. An einzel lens is a lens that focuses without changing the energy of the beam. It consists of three or more sets of cylindrical or rectangular tubes in series along an axis, the quadrupole lens consists of two single quadrupoles turned 90° with respect to each other. Let z be the axis then one can deduce separately for the x. A magnetic quadrupole works very similar to an electric quadrupole, but the Lorentz force increases with the velocity of the charged particle. In spirit of a Wien filter a combined magnetic, electric quadrupole is achromatic around a given velocity, bohr and Pauli claim that this lens leads to aberration when applied to ions with spin, but not when applied to electrons, which also have a spin. Instead of an electrostatic field we can use a magnetic field to focus charged particles
3.
Lens (optics)
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A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a piece of transparent material, while a compound lens consists of several simple lenses. Lenses are made from such as glass or plastic, and are ground. A lens can focus light to form an image, unlike a prism, devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. The word lens comes from the Latin name of the lentil, the genus of the lentil plant is Lens, and the most commonly eaten species is Lens culinaris. The lentil plant also gives its name to a geometric figure, the variant spelling lense is sometimes seen. While it is listed as a spelling in some dictionaries. The oldest lens artifact is the Nimrud lens, dating back 2700 years to ancient Assyria, david Brewster proposed that it may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight. Another early reference to magnification dates back to ancient Egyptian hieroglyphs in the 8th century BC, the earliest written records of lenses date to Ancient Greece, with Aristophanes play The Clouds mentioning a burning-glass. Some scholars argue that the evidence indicates that there was widespread use of lenses in antiquity. Such lenses were used by artisans for fine work, and for authenticating seal impressions, both Pliny and Seneca the Younger described the magnifying effect of a glass globe filled with water. The Viking lenses were capable of concentrating enough sunlight to ignite fires, between the 11th and 13th century reading stones were invented. Often used by monks to assist in illuminating manuscripts, these were primitive plano-convex lenses initially made by cutting a sphere in half. As the stones were experimented with, it was understood that shallower lenses magnified more effectively. Lenses came into use in Europe with the invention of spectacles. Spectacle makers created improved types of lenses for the correction of vision based more on knowledge gained from observing the effects of the lenses. With the invention of the telescope and microscope there was a deal of experimentation with lens shapes in the 17th. Opticians tried to construct lenses of varying forms of curvature, wrongly assuming errors arose from defects in the figure of their surfaces
4.
Electron microscope
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An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. Transmission electron microscopes use electrostatic and electromagnetic lenses to control the electron beam and these electron optical lenses are analogous to the glass lenses of an optical light microscope. Industrially, electron microscopes are used for quality control and failure analysis. Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the image, the first electromagnetic lens was developed in 1926 by Hans Busch. According to Dennis Gabor, the physicist Leó Szilárd tried in 1928 to convince Busch to build an electron microscope, two years later, in 1933, Ruska built an electron microscope that exceeded the resolution attainable with an optical microscope. Moreover, Reinhold Rudenberg, the director of Siemens-Schuckertwerke, obtained the patent for the electron microscope in May 1931. In 1932, Ernst Lubcke of Siemens & Halske built and obtained images from an electron microscope. Five years later, the firm financed the work of Ernst Ruska and Bodo von Borries, also in 1937, Manfred von Ardenne pioneered the scanning electron microscope. The first commercial electron microscope was produced in 1938 by Siemens, although contemporary transmission electron microscopes are capable of two million-power magnification, as scientific instruments, they remain based upon Ruska’s prototype. The original form of electron microscope, the electron microscope uses a high voltage electron beam to illuminate the specimen. The electron beam is produced by a gun, commonly fitted with a tungsten filament cathode as the electron source. When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by the lens system of the microscope. The image detected by the camera may be displayed on a monitor or computer. The resolution of TEMs is limited primarily by spherical aberration, but a new generation of aberration correctors have been able to partially overcome spherical aberration to increase resolution. The ability to determine the positions of atoms within materials has made the HRTEM an important tool for nano-technologies research, transmission electron microscopes are often used in electron diffraction mode. The major disadvantage of the electron microscope is the need for extremely thin sections of the specimens. Biological specimens are required to be chemically fixed, dehydrated and embedded in a polymer resin to stabilize them sufficiently to allow ultrathin sectioning. Sections of biological specimens, organic polymers and similar materials may require treatment with heavy atom labels in order to achieve the required image contrast
5.
Particle accelerator
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A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to nearly light speed and to contain them in well-defined beams. Large accelerators are used in physics as colliders, or as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world, there are two basic classes of accelerators, electrostatic and electrodynamic accelerators. Electrostatic accelerators use electric fields to accelerate particles. The most common types are the Cockcroft–Walton generator and the Van de Graaff generator, a small-scale example of this class is the cathode ray tube in an ordinary old television set. The achievable kinetic energy for particles in these devices is determined by the accelerating voltage, electrodynamic or electromagnetic accelerators, on the other hand, use changing electromagnetic fields to accelerate particles. Since in these types the particles can pass through the accelerating field multiple times. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators, because colliders can give evidence of the structure of the subatomic world, accelerators were commonly referred to as atom smashers in the 20th century. Despite the fact that most accelerators actually propel subatomic particles, the term persists in popular usage when referring to particle accelerators in general. Beams of high-energy particles are useful for both fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research and it has been estimated that there are approximately 30,000 accelerators worldwide. The bar graph shows the breakdown of the number of industrial accelerators according to their applications, for the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV, and the interactions of the simplest kinds of particles, leptons and quarks for the matter, the largest and highest energy particle accelerator used for elementary particle physics is the Large Hadron Collider at CERN, operating since 2009. These investigations often involve collisions of heavy nuclei – of atoms like iron or gold – at energies of several GeV per nucleon, the largest such particle accelerator is the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. An example of type of machine is LANSCE at Los Alamos. A large number of light sources exist worldwide. The ESRF in Grenoble, France has been used to extract detailed 3-dimensional images of trapped in amber. Thus there is a demand for electron accelerators of moderate energy. Everyday examples of particle accelerators are cathode ray tubes found in television sets and these low-energy accelerators use a single pair of electrodes with a DC voltage of a few thousand volts between them
6.
Paraxial approximation
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In geometric optics, the paraxial approximation is a small-angle approximation used in Gaussian optics and ray tracing of light through an optical system. A paraxial ray is a ray which makes an angle to the optical axis of the system. Generally, this allows three important approximations for calculation of the path, namely, sin θ ≈ θ, tan θ ≈ θ. The paraxial approximation is used in Gaussian optics and first-order ray tracing, ray transfer matrix analysis is one method that uses the approximation. In some cases, the approximation is also called paraxial. The approximations above for sine and tangent do not change for the second-order paraxial approximation, the second-order approximation is accurate within 0. 5% for angles under about 10°, but its inaccuracy grows significantly for larger angles. For larger angles it is necessary to distinguish between meridional rays, which lie in a plane containing the optical axis, and sagittal rays. Paraxial Approximation and the Mirror by David Schurig, The Wolfram Demonstrations Project
7.
Einzel lens
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An einzel lens, or unipotential lens, is a charged particle lens that focuses without changing the energy of the beam. It consists of three or more sets of cylindrical or rectangular apertures or tubes in series along an axis and it is used in ion optics to focus ions in flight, which is accomplished through manipulation of the electric field in the path of the ions. This causes the particles to arrive at the focus intersection slightly later than the ones that travel along a straight path. If the lens is constructed with cylindrical electrodes, the field is symmetrical around z, the integral occurs over the gap between the plates. This is also the interval where the lensing occurs, the pair of plates is also called an electrostatic immersion lens, thus an einzel lens can be described as two or more electrostatic immersion lenses. Solving the equation above twice to find the change in velocity for each pair of plates can be used to calculate the focal length of the lens. Time of flight Mass spectrometry Cathode ray tube Aberth, William H, construction of an einzel lens capable of high voltage operation, Review of Scientific Instruments,45,1289, Bibcode, 1974RScI.45. 1289A, doi,10. 1063/1.1686484
