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159-461: The ILC would collide electrons with positrons . It will be between 30 km and 50 km (19–31 mi) long, more than 10 times as long as the 50 GeV Stanford Linear Accelerator , the longest existing linear particle accelerator. The proposal is based on previous similar proposals from Europe, the U.S., and Japan. In a staged approach, the ILC could initially be constructed at 250 GeV, for use as

318-642: A Higgs factory . Such a design would be approximately 20 km in length. Studies for an alternative project, the Compact Linear Collider (CLIC) are also underway, which would operate at higher energies (up to 3 TeV) in a machine of length similar to the ILC. These two projects, CLIC and the ILC, have been unified under the Linear Collider Collaboration . There are two basic shapes of accelerators. Linear accelerators ("linacs") accelerate elementary particles along

477-404: A de Broglie wave in the manner of light . That is, under the appropriate conditions, electrons and other matter would show properties of either particles or waves. The corpuscular properties of a particle are demonstrated when it is shown to have a localized position in space along its trajectory at any given moment. The wave-like nature of light is displayed, for example, when a beam of light

636-519: A gain medium , a mechanism to energize it, and something to provide optical feedback . The gain medium is a material with properties that allow it to amplify light by way of stimulated emission. Light of a specific wavelength that passes through the gain medium is amplified (power increases). Feedback enables stimulated emission to amplify predominantly the optical frequency at the peak of the gain-frequency curve. As stimulated emission grows, eventually one frequency dominates over all others, meaning that

795-471: A lens system, as is always included, for instance, in a laser pointer whose light originates from a laser diode . That is possible due to the light being of a single spatial mode. This unique property of laser light, spatial coherence , cannot be replicated using standard light sources (except by discarding most of the light) as can be appreciated by comparing the beam from a flashlight (torch) or spotlight to that of almost any laser. A laser beam profiler

954-464: A broad spectrum of light or emit different wavelengths of light simultaneously. Certain lasers are not single spatial mode and have light beams that diverge more than is required by the diffraction limit . All such devices are classified as "lasers" based on the method of producing light by stimulated emission. Lasers are employed where light of the required spatial or temporal coherence can not be produced using simpler technologies. A laser consists of

1113-504: A chain reaction. The materials chosen for lasers are the ones that have metastable states , which stay excited for a relatively long time. In laser physics , such a material is called an active laser medium . Combined with an energy source that continues to "pump" energy into the material, it is possible to have enough atoms or molecules in an excited state for a chain reaction to develop. Lasers are distinguished from other light sources by their coherence . Spatial (or transverse) coherence

1272-648: A charged droplet of oil from falling as a result of gravity. This device could measure the electric charge from as few as 1–150 ions with an error margin of less than 0.3%. Comparable experiments had been done earlier by Thomson's team, using clouds of charged water droplets generated by electrolysis, and in 1911 by Abram Ioffe , who independently obtained the same result as Millikan using charged microparticles of metals, then published his results in 1913. However, oil drops were more stable than water drops because of their slower evaporation rate, and thus more suited to precise experimentation over longer periods of time. Around

1431-436: A coherent beam has been formed. The process of stimulated emission is analogous to that of an audio oscillator with positive feedback which can occur, for example, when the speaker in a public-address system is placed in proximity to the microphone. The screech one hears is audio oscillation at the peak of the gain-frequency curve for the amplifier. For the gain medium to amplify light, it needs to be supplied with energy in

1590-419: A device lacks the spatial and temporal coherence achievable with lasers. Such a device cannot be described as an oscillator but rather as a high-gain optical amplifier that amplifies its spontaneous emission. The same mechanism describes so-called astrophysical masers /lasers. The optical resonator is sometimes referred to as an "optical cavity", but this is a misnomer: lasers use open resonators as opposed to

1749-410: A fourth state of matter in which the mean free path of the particles is so long that collisions may be ignored. In 1883, not yet well-known German physicist Heinrich Hertz tried to prove that cathode rays are electrically neutral and got what he interpreted as a confident absence of deflection in electrostatic, as opposed to magnetic, field. However, as J. J. Thomson explained in 1897, Hertz placed

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1908-494: A friction that slows the electron. This force is caused by a back-reaction of the electron's own field upon itself. Photons mediate electromagnetic interactions between particles in quantum electrodynamics . An isolated electron at a constant velocity cannot emit or absorb a real photon; doing so would violate conservation of energy and momentum . Instead, virtual photons can transfer momentum between two charged particles. This exchange of virtual photons, for example, generates

2067-508: A gain medium must have a gain bandwidth sufficiently broad to amplify those frequencies. An example of a suitable material is titanium -doped, artificially grown sapphire ( Ti:sapphire ), which has a very wide gain bandwidth and can thus produce pulses of only a few femtoseconds duration. Such mode-locked lasers are a most versatile tool for researching processes occurring on extremely short time scales (known as femtosecond physics, femtosecond chemistry and ultrafast science ), for maximizing

2226-480: A given pulse energy, this requires creating pulses of the shortest possible duration utilizing techniques such as Q-switching . The optical bandwidth of a pulse cannot be narrower than the reciprocal of the pulse width. In the case of extremely short pulses, that implies lasing over a considerable bandwidth, quite contrary to the very narrow bandwidths typical of CW lasers. The lasing medium in some dye lasers and vibronic solid-state lasers produces optical gain over

2385-560: A half-integer value, expressed in units of the reduced Planck constant , ħ . Being fermions , no two electrons can occupy the same quantum state , per the Pauli exclusion principle . Like all elementary particles, electrons exhibit properties of both particles and waves : They can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have

2544-399: A higher energy level with energy difference ΔE, it will not stay that way forever. Eventually, a photon will be spontaneously created from the vacuum having energy ΔE. Conserving energy, the electron transitions to a lower energy level that is not occupied, with transitions to different levels having different time constants. This process is called spontaneous emission . Spontaneous emission is

2703-904: A laser beam to stay narrow over great distances ( collimation ), a feature used in applications such as laser pointers , lidar , and free-space optical communication . Lasers can also have high temporal coherence , which permits them to emit light with a very narrow frequency spectrum . Temporal coherence can also be used to produce ultrashort pulses of light with a broad spectrum but durations as short as an attosecond . Lasers are used in optical disc drives , laser printers , barcode scanners , DNA sequencing instruments , fiber-optic and free-space optical communications, semiconductor chip manufacturing ( photolithography , etching ), laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Semiconductor lasers in

2862-476: A laser beam, it is highly collimated : the wavefronts are planar, normal to the direction of propagation, with no beam divergence at that point. However, due to diffraction , that can only remain true well within the Rayleigh range . The beam of a single transverse mode (gaussian beam) laser eventually diverges at an angle that varies inversely with the beam diameter, as required by diffraction theory. Thus,

3021-471: A laser is normally a material of controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission described above. This material can be of any state : gas, liquid, solid, or plasma . The gain medium absorbs pump energy, which raises some electrons into higher energy (" excited ") quantum states . Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. In

3180-406: A linear accelerator, the remaining particles are lost; in a ring accelerator, they keep circulating and are available for future collisions. The disadvantage of circular accelerators is that charged particles moving along bent paths will necessarily emit electromagnetic radiation known as synchrotron radiation . Energy loss through synchrotron radiation is inversely proportional to the fourth power of

3339-429: A lower mass and hence a longer de Broglie wavelength for a given energy. Electrons play an essential role in numerous physical phenomena, such as electricity , magnetism , chemistry , and thermal conductivity ; they also participate in gravitational , electromagnetic , and weak interactions . Since an electron has charge, it has a surrounding electric field ; if that electron is moving relative to an observer,

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3498-464: A model of the electron – the Dirac equation , consistent with relativity theory, by applying relativistic and symmetry considerations to the hamiltonian formulation of the quantum mechanics of the electro-magnetic field. In order to resolve some problems within his relativistic equation, Dirac developed in 1930 a model of the vacuum as an infinite sea of particles with negative energy, later dubbed

3657-418: A multi-level system as a method for obtaining the population inversion, later a main method of laser pumping. Townes reports that several eminent physicists—among them Niels Bohr , John von Neumann , and Llewellyn Thomas —argued the maser violated Heisenberg's uncertainty principle and hence could not work. Others such as Isidor Rabi and Polykarp Kusch expected that it would be impractical and not worth

3816-456: A particle with a positive charge, such as the proton, and a repulsive force on a particle with a negative charge. The strength of this force in nonrelativistic approximation is determined by Coulomb's inverse square law . When an electron is in motion, it generates a magnetic field . The Ampère–Maxwell law relates the magnetic field to the mass motion of electrons (the current ) with respect to an observer. This property of induction supplies

3975-441: A process called pumping . The energy is typically supplied as an electric current or as light at a different wavelength. Pump light may be provided by a flash lamp or by another laser. The most common type of laser uses feedback from an optical cavity —a pair of mirrors on either end of the gain medium. Light bounces back and forth between the mirrors, passing through the gain medium and being amplified each time. Typically one of

4134-468: A quantum-mechanical effect and a direct physical manifestation of the Heisenberg uncertainty principle . The emitted photon has a random direction, but its wavelength matches the absorption wavelength of the transition. This is the mechanism of fluorescence and thermal emission . A photon with the correct wavelength to be absorbed by a transition can also cause an electron to drop from the higher to

4293-432: A seminar on this idea, and Charles H. Townes asked him for a copy of the paper. In 1953, Charles H. Townes and graduate students James P. Gordon and Herbert J. Zeiger produced the first microwave amplifier, a device operating on similar principles to the laser, but amplifying microwave radiation rather than infrared or visible radiation. Townes's maser was incapable of continuous output. Meanwhile, in

4452-400: A separate linac. To compact the 5 GeV electron and positron bunches to a sufficiently small size to be usefully collided, they will circulate for 0.1–0.2 seconds in a pair of damping rings, 3.24 km in circumference, in which they will be reduced in size to 6 mm in length and a vertical and horizontal emittance of 2 pm and 0.6 nm, respectively. From the damping rings

4611-553: A single electron. This prohibition against more than one electron occupying the same quantum energy state became known as the Pauli exclusion principle . The physical mechanism to explain the fourth parameter, which had two distinct possible values, was provided by the Dutch physicists Samuel Goudsmit and George Uhlenbeck . In 1925, they suggested that an electron, in addition to the angular momentum of its orbit, possesses an intrinsic angular momentum and magnetic dipole moment . This

4770-431: A small volume of material at the surface of a workpiece can be evaporated if it is heated in a very short time, while supplying the energy gradually would allow for the heat to be absorbed into the bulk of the piece, never attaining a sufficiently high temperature at a particular point. Other applications rely on the peak pulse power (rather than the energy in the pulse), especially to obtain nonlinear optical effects. For

4929-482: A solution that determined the location of an electron over time, this wave equation also could be used to predict the probability of finding an electron near a position, especially a position near where the electron was bound in space, for which the electron wave equations did not change in time. This approach led to a second formulation of quantum mechanics (the first by Heisenberg in 1925), and solutions of Schrödinger's equation, like Heisenberg's, provided derivations of

International Linear Collider - Misplaced Pages Continue

5088-599: A straight path. Circular accelerators ("synchrotrons"), such as the Tevatron , the LEP , and the Large Hadron Collider (LHC), use circular paths. Circular geometry has significant advantages at energies up to and including tens of GeV : With a circular design, particles can be effectively accelerated over longer distances. Also, only a fraction of the particles brought onto a collision course actually collide. In

5247-720: A summary of that contained in the International Workshop on Linear Colliders 2010 (ECFA-CLIC-ILC Joint Meeting) at CERN. The 2008 economic crisis led the United States and United Kingdom to cut funds to the collider project, leading to Japan's position as the most likely host for the International Linear Collider. On August 23, 2013, the Japanese high-energy physics community's site evaluation committee proposed it should be located in

5406-437: A surplus of the charge carrier, and which situation was a deficit. Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges . Beginning in 1846, German physicist Wilhelm Eduard Weber theorized that electricity was composed of positively and negatively charged fluids, and their interaction

5565-430: A wide bandwidth, making a laser possible that can thus generate pulses of light as short as a few femtoseconds (10 s). In a Q-switched laser, the population inversion is allowed to build up by introducing loss inside the resonator which exceeds the gain of the medium; this can also be described as a reduction of the quality factor or 'Q' of the cavity. Then, after the pump energy stored in the laser medium has approached

5724-492: A wide range of technologies addressing many different motivations. Some lasers are pulsed simply because they cannot be run in continuous mode. In other cases, the application requires the production of pulses having as large an energy as possible. Since the pulse energy is equal to the average power divided by the repetition rate, this goal can sometimes be satisfied by lowering the rate of pulses so that more energy can be built up between pulses. In laser ablation , for example,

5883-435: Is a subatomic particle with a negative one elementary electric charge . Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron's mass is approximately 1/1836 that of the proton . Quantum mechanical properties of the electron include an intrinsic angular momentum ( spin ) of

6042-407: Is a challenging problem of modern theoretical physics. The admission of the hypothesis of a finite radius of the electron is incompatible to the premises of the theory of relativity. On the other hand, a point-like electron (zero radius) generates serious mathematical difficulties due to the self-energy of the electron tending to infinity. Observation of a single electron in a Penning trap suggests

6201-467: Is a combination of the words electr ic and i on . The suffix - on which is now used to designate other subatomic particles, such as a proton or neutron, is in turn derived from electron. While studying electrical conductivity in rarefied gases in 1859, the German physicist Julius Plücker observed the radiation emitted from the cathode caused phosphorescent light to appear on the tube wall near

6360-404: Is a transition between energy levels that match the energy carried by the photon or phonon. For light, this means that any given transition will only absorb one particular wavelength of light. Photons with the correct wavelength can cause an electron to jump from the lower to the higher energy level. The photon is consumed in this process. When an electron is excited from one state to that at

6519-496: Is actually smaller than its true value, and the charge decreases with increasing distance from the electron. This polarization was confirmed experimentally in 1997 using the Japanese TRISTAN particle accelerator. Virtual particles cause a comparable shielding effect for the mass of the electron. The interaction with virtual particles also explains the small (about 0.1%) deviation of the intrinsic magnetic moment of

International Linear Collider - Misplaced Pages Continue

6678-480: Is also required for three-level lasers in which the lower energy level rapidly becomes highly populated, preventing further lasing until those atoms relax to the ground state. These lasers, such as the excimer laser and the copper vapor laser, can never be operated in CW mode. In 1917, Albert Einstein established the theoretical foundations for the laser and the maser in the paper " Zur Quantentheorie der Strahlung " ("On

6837-592: Is analogous to the rotation of the Earth on its axis as it orbits the Sun. The intrinsic angular momentum became known as spin , and explained the previously mysterious splitting of spectral lines observed with a high-resolution spectrograph ; this phenomenon is known as fine structure splitting. In his 1924 dissertation Recherches sur la théorie des quanta (Research on Quantum Theory), French physicist Louis de Broglie hypothesized that all matter can be represented as

6996-479: Is approximately 9.109 × 10  kg , or 5.489 × 10   Da . Due to mass–energy equivalence , this corresponds to a rest energy of 0.511 MeV (8.19 × 10  J) . The ratio between the mass of a proton and that of an electron is about 1836. Astronomical measurements show that the proton-to-electron mass ratio has held the same value, as is predicted by the Standard Model, for at least half

7155-413: Is called an optical amplifier . When an optical amplifier is placed inside a resonant optical cavity, one obtains a laser. For lasing media with extremely high gain, so-called superluminescence , light can be sufficiently amplified in a single pass through the gain medium without requiring a resonator. Although often referred to as a laser (see, for example, nitrogen laser ), the light output from such

7314-462: Is emitted by stimulated emission is identical to the photon that triggered its emission, and both photons can go on to trigger stimulated emission in other atoms, creating the possibility of a chain reaction . For this to happen, many of the atoms or molecules must be in the proper excited state so that the photons can trigger them. In most materials, atoms or molecules drop out of excited states fairly rapidly, making it difficult or impossible to produce

7473-421: Is formed by single-frequency quantum photon states distributed according to a Poisson distribution . As a result, the arrival rate of photons in a laser beam is described by Poisson statistics. Many lasers produce a beam that can be approximated as a Gaussian beam ; such beams have the minimum divergence possible for a given beam diameter. Some lasers, particularly high-power ones, produce multimode beams, with

7632-443: Is frequently used in the field, meaning "to give off coherent light," especially about the gain medium of a laser; when a laser is operating, it is said to be " lasing ". The terms laser and maser are also used for naturally occurring coherent emissions, as in astrophysical maser and atom laser . A laser that produces light by itself is technically an optical oscillator rather than an optical amplifier as suggested by

7791-421: Is impossible. In some other lasers, it would require pumping the laser at a very high continuous power level, which would be impractical, or destroying the laser by producing excessive heat. Such lasers cannot be run in CW mode. The pulsed operation of lasers refers to any laser not classified as a continuous wave so that the optical power appears in pulses of some duration at some repetition rate. This encompasses

7950-455: Is in existence, the Coulomb force from the ambient electric field surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called vacuum polarization . In effect, the vacuum behaves like a medium having a dielectric permittivity more than unity . Thus the effective charge of an electron

8109-405: Is not the result of random thermal processes. Instead, the release of a photon is triggered by the nearby passage of another photon. This is called stimulated emission . For this process to work, the passing photon must be similar in energy, and thus wavelength, to the one that could be released by the atom or molecule, and the atom or molecule must be in the suitable excited state. The photon that

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8268-570: Is one of humanity's earliest recorded experiences with electricity . In his 1600 treatise De Magnete , the English scientist William Gilbert coined the Neo-Latin term electrica , to refer to those substances with property similar to that of amber which attract small objects after being rubbed. Both electric and electricity are derived from the Latin ēlectrum (also the root of

8427-407: Is passed through parallel slits thereby creating interference patterns. In 1927, George Paget Thomson and Alexander Reid discovered the interference effect was produced when a beam of electrons was passed through thin celluloid foils and later metal films, and by American physicists Clinton Davisson and Lester Germer by the reflection of electrons from a crystal of nickel . Alexander Reid, who

8586-489: Is to heat an object; some of the thermal energy being applied to the object will cause the molecules and electrons within the object to gain energy, which is then lost through thermal radiation , that we see as light. This is the process that causes a candle flame to give off light. Thermal radiation is a random process, and thus the photons emitted have a range of different wavelengths , travel in different directions, and are released at different times. The energy within

8745-504: Is to pump the laser material with a source that is itself pulsed, either through electronic charging in the case of flash lamps, or another laser that is already pulsed. Pulsed pumping was historically used with dye lasers where the inverted population lifetime of a dye molecule was so short that a high-energy, fast pump was needed. The way to overcome this problem was to charge up large capacitors which are then switched to discharge through flashlamps, producing an intense flash. Pulsed pumping

8904-441: Is typically expressed through the output being a narrow beam, which is diffraction-limited . Laser beams can be focused to very tiny spots, achieving a very high irradiance , or they can have a very low divergence to concentrate their power at a great distance. Temporal (or longitudinal) coherence implies a polarized wave at a single frequency, whose phase is correlated over a relatively great distance (the coherence length ) along

9063-430: Is used to measure the intensity profile, width, and divergence of laser beams. Diffuse reflection of a laser beam from a matte surface produces a speckle pattern with interesting properties. The mechanism of producing radiation in a laser relies on stimulated emission , where energy is extracted from a transition in an atom or molecule. This is a quantum phenomenon that was predicted by Albert Einstein , who derived

9222-461: The Dirac sea . This led him to predict the existence of a positron, the antimatter counterpart of the electron. This particle was discovered in 1932 by Carl Anderson , who proposed calling standard electrons negatrons and using electron as a generic term to describe both the positively and negatively charged variants. In 1947, Willis Lamb , working in collaboration with graduate student Robert Retherford , found that certain quantum states of

9381-529: The Kannagawa Hydropower Plant ). Following the closure of the Tevatron some groups within the USA had expressed interest, with Fermilab being a favored site because of the facilities and experts already present. Much of the speculated interest from other countries was hearsay from within the scientific community, and very few facts were published officially. The information presented above is

9540-662: The Kitakami Mountains of the Iwate and Miyagi Prefectures . As of March 7, 2019, the Japanese government has stated that it is not ready to support the construction of the Collider due to its high proposed cost of approximately $ 7 billion. This decision was informed partly by the Science Council of Japan . The Japanese government sought monetary support from other countries to help fund this project. In 2022,

9699-458: The Lamb shift observed in spectral lines . The Compton Wavelength shows that near elementary particles such as the electron, the uncertainty of the energy allows for the creation of virtual particles near the electron. This wavelength explains the "static" of virtual particles around elementary particles at a close distance. An electron generates an electric field that exerts an attractive force on

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9858-476: The Standard Model of particle physics. Individual electrons can now be easily confined in ultra small ( L = 20 nm , W = 20 nm ) CMOS transistors operated at cryogenic temperature over a range of −269 °C (4  K ) to about −258 °C (15  K ). The electron wavefunction spreads in a semiconductor lattice and negligibly interacts with the valence band electrons, so it can be treated in

10017-416: The absolute value of this function is squared , it gives the probability that a particle will be observed near a location—a probability density . Electrons are identical particles because they cannot be distinguished from each other by their intrinsic physical properties. In quantum mechanics, this means that a pair of interacting electrons must be able to swap positions without an observable change to

10176-414: The age of the universe . Electrons have an electric charge of −1.602 176 634 × 10 coulombs , which is used as a standard unit of charge for subatomic particles, and is also called the elementary charge . Within the limits of experimental accuracy, the electron charge is identical to the charge of a proton, but with the opposite sign. The electron is commonly symbolized by e , and

10335-726: The alloy of the same name ), which came from the Greek word for amber, ἤλεκτρον ( ēlektron ). In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids , vitreous fluid from glass rubbed with silk and resinous fluid from amber rubbed with wool. These two fluids can neutralize each other when combined. American scientist Ebenezer Kinnersley later also independently reached

10494-405: The double-slit experiment . The wave-like nature of the electron allows it to pass through two parallel slits simultaneously, rather than just one slit as would be the case for a classical particle. In quantum mechanics, the wave-like property of one particle can be described mathematically as a complex -valued function, the wave function , commonly denoted by the Greek letter psi ( ψ ). When

10653-462: The e / m ratio but did not take the step of interpreting their results as showing a new particle, while J. J. Thomson would subsequently in 1899 give estimates for the electron charge and mass as well: e  ~  6.8 × 10   esu and m  ~  3 × 10  g The name "electron" was adopted for these particles by the scientific community, mainly due to the advocation by G. F. FitzGerald , J. Larmor , and H. A. Lorentz . The term

10812-578: The mass of the particles in question. That is why it makes sense to build circular accelerators for heavy particles—hadron colliders such as the LHC for protons or, alternatively, for lead nuclei . An electron–positron collider of the same size would never be able to achieve the same collision energies. In fact, energies at the LEP which used to occupy the tunnel now given over to the LHC, were limited to 209 GeV by energy loss via synchrotron radiation. Even though

10971-414: The muon and the tau , which are identical to the electron in charge, spin and interactions , but are more massive. Leptons differ from the other basic constituent of matter, the quarks , by their lack of strong interaction . All members of the lepton group are fermions because they all have half-odd integer spin; the electron has spin ⁠ 1 / 2 ⁠ . The invariant mass of an electron

11130-410: The phase of the emitted light is 90 degrees in lead of the stimulating light. This, combined with the filtering effect of the optical resonator gives laser light its characteristic coherence, and may give it uniform polarization and monochromaticity, depending on the resonator's design. The fundamental laser linewidth of light emitted from the lasing resonator can be orders of magnitude narrower than

11289-459: The spectral lines of the hydrogen atom. However, Bohr's model failed to account for the relative intensities of the spectral lines and it was unsuccessful in explaining the spectra of more complex atoms. Chemical bonds between atoms were explained by Gilbert Newton Lewis , who in 1916 proposed that a covalent bond between two atoms is maintained by a pair of electrons shared between them. Later, in 1927, Walter Heitler and Fritz London gave

11448-399: The spinon , the orbiton and the holon (or chargon). The electron can always be theoretically considered as a bound state of the three, with the spinon carrying the spin of the electron, the orbiton carrying the orbital degree of freedom and the chargon carrying the charge, but in certain conditions they can behave as independent quasiparticles . The issue of the radius of the electron

11607-421: The transverse modes often approximated using Hermite – Gaussian or Laguerre -Gaussian functions. Some high-power lasers use a flat-topped profile known as a " tophat beam ". Unstable laser resonators (not used in most lasers) produce fractal-shaped beams. Specialized optical systems can produce more complex beam geometries, such as Bessel beams and optical vortexes . Near the "waist" (or focal region ) of

11766-505: The "pencil beam" directly generated by a common helium–neon laser would spread out to a size of perhaps 500 kilometers when shone on the Moon (from the distance of the Earth). On the other hand, the light from a semiconductor laser typically exits the tiny crystal with a large divergence: up to 50°. However even such a divergent beam can be transformed into a similarly collimated beam employing

11925-599: The 1870s, the English chemist and physicist Sir William Crookes developed the first cathode-ray tube to have a high vacuum inside. He then showed in 1874 that the cathode rays can turn a small paddle wheel when placed in their path. Therefore, he concluded that the rays carried momentum. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged. In 1879, he proposed that these properties could be explained by regarding cathode rays as composed of negatively charged gaseous molecules in

12084-477: The Coulomb force. Energy emission can occur when a moving electron is deflected by a charged particle, such as a proton. The deceleration of the electron results in the emission of Bremsstrahlung radiation. An inelastic collision between a photon (light) and a solitary (free) electron is called Compton scattering . This collision results in a transfer of momentum and energy between the particles, which modifies

12243-422: The ILC project's progress and initiatives by relevant organizations". Fifty participants, including Diet members and other government agencies, as well as researchers and businesses, received reports on the project's progress. Participants discussed the ILC's future. The meeting resulted in three recommendations: 1. The ILC project will be further promoted by the research community, industry, organizations promoting

12402-478: The ILC will use 2-nanosecond laser light pulses to eject electrons from a photocathode , a technique allowing for up to 80% of the electrons to be polarized; the electrons then will be accelerated to 5 GeV in a 370-meter linac stage. Synchrotron radiation from high energy electrons will produce electron-positron pairs on a titanium-alloy target, with as much as 60% polarization; the positrons from these collisions will be collected and accelerated to 5 GeV in

12561-848: The International Committee for Future Accelerators (ICFA) announced Prof. Barry Barish , director of the LIGO Laboratory at Caltech from 1997 to 2005, as the Director of the Global Design Effort (GDE). In August 2007, the Reference Design Report for the ILC was released. Physicists working on the GDE completed a detailed ILC design report, publishing it in June 2013. The electron source for

12720-712: The International Technology Recommendation Panel (ITRP) recommended a superconducting radio frequency technology for the accelerator. After this decision the three existing linear collider projects – the Next Linear Collider (NLC), the Global Linear Collider (GLC) and Teraelectronvolt Energy Superconducting Linear Accelerator (TESLA) – joined their efforts into one single project (the ILC). In March 2005,

12879-546: The Japanese plan for the ILC was "shelved" by a panel for Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT) Several reasons were given, including potentially insufficient international support and the CERN proposal for the Future Circular Collider , which has overlapping physics goals with the ILC. In March 2024, the "Federation of Diet Members for the ILC" met to receive "Reports on

13038-677: The Quantum Theory of Radiation") via a re-derivation of Max Planck 's law of radiation, conceptually based upon probability coefficients ( Einstein coefficients ) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation. In 1928, Rudolf W. Ladenburg confirmed the existence of the phenomena of stimulated emission and negative absorption. In 1939, Valentin A. Fabrikant predicted using stimulated emission to amplify "short" waves. In 1947, Willis E. Lamb and R.   C.   Retherford found apparent stimulated emission in hydrogen spectra and effected

13197-509: The Soviet Union, Nikolay Basov and Aleksandr Prokhorov were independently working on the quantum oscillator and solved the problem of continuous-output systems by using more than two energy levels. These gain media could release stimulated emissions between an excited state and a lower excited state, not the ground state, facilitating the maintenance of a population inversion . In 1955, Prokhorov and Basov suggested optical pumping of

13356-614: The acronym. It has been humorously noted that the acronym LOSER, for "light oscillation by stimulated emission of radiation", would have been more correct. With the widespread use of the original acronym as a common noun, optical amplifiers have come to be referred to as laser amplifiers . Modern physics describes light and other forms of electromagnetic radiation as the group behavior of fundamental particles known as photons . Photons are released and absorbed through electromagnetic interactions with other fundamental particles that carry electric charge . A common way to release photons

13515-420: The atmosphere. The antiparticle of the electron is called the positron ; it is identical to the electron, except that it carries electrical charge of the opposite sign. When an electron collides with a positron , both particles can be annihilated , producing gamma ray photons . The ancient Greeks noticed that amber attracted small objects when rubbed with fur. Along with lightning , this phenomenon

13674-476: The beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase that vary randomly with respect to time and position, thus having a short coherence length. Lasers are characterized according to their wavelength in a vacuum . Most "single wavelength" lasers produce radiation in several modes with slightly different wavelengths. Although temporal coherence implies some degree of monochromaticity , some lasers emit

13833-480: The beginning of the twentieth century, it was found that under certain conditions a fast-moving charged particle caused a condensation of supersaturated water vapor along its path. In 1911, Charles Wilson used this principle to devise his cloud chamber so he could photograph the tracks of charged particles, such as fast-moving electrons. By 1914, experiments by physicists Ernest Rutherford , Henry Moseley , James Franck and Gustav Hertz had largely established

13992-425: The blue to near-UV have also been used in place of light-emitting diodes (LEDs) to excite fluorescence as a white light source; this permits a much smaller emitting area due to the much greater radiance of a laser and avoids the droop suffered by LEDs; such devices are already used in some car headlamps . The first device using amplification by stimulated emission operated at microwave frequencies, and

14151-530: The bunches will be focused to a few nanometers in height and a few hundred nanometers in width. The focused bunches then will be collided inside one of two large particle detectors . Originally, three sites for the International Linear Collider were leading contenders at established High Energy Physics centers in Europe. At CERN in Geneva the tunnel is located deep underground in non-permeable bedrock. This site

14310-589: The candidate sites, relevant ministries and agencies, the Diet members and other political organizations within an all-Japan framework. 2. For the ILC project, international collaboration will be further strengthened as a global initiative involving the research community. This will be achieved through close cooperation between the ILC International Development Team (IDT), an international promotion organization established under ICFA, and

14469-402: The cathode; and the region of the phosphorescent light could be moved by application of a magnetic field. In 1869, Plücker's student Johann Wilhelm Hittorf found that a solid body placed in between the cathode and the phosphorescence would cast a shadow upon the phosphorescent region of the tube. Hittorf inferred that there are straight rays emitted from the cathode and that the phosphorescence

14628-553: The charge carriers were much heavier hydrogen or nitrogen atoms. Schuster's estimates would subsequently turn out to be largely correct. In 1892 Hendrik Lorentz suggested that the mass of these particles (electrons) could be a consequence of their electric charge. While studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became

14787-588: The concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge "electron" in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897 during the cathode-ray tube experiment . Electrons participate in nuclear reactions , such as nucleosynthesis in stars , where they are known as beta particles . Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance, when cosmic rays enter

14946-512: The cost of building the ILC, excluding R&D, prototyping, land acquisition, underground easement costs, detectors, contingencies, and inflation, at US$ 6.75 billion (in 2007 prices). From formal project approval, completion of the accelerator complex and detectors is expected to require seven years. The host country would be required to pay $ 1.8 billion for site-specific costs like digging tunnels and shafts and supplying water and electricity. Former U.S. Secretary of Energy Steven Chu estimated

15105-430: The deflecting electrodes in a highly-conductive area of the tube, resulting in a strong screening effect close to their surface. The German-born British physicist Arthur Schuster expanded upon Crookes's experiments by placing metal plates parallel to the cathode rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that

15264-618: The domestic research community. 3. The Ministry of Education, Culture, Sports, Science and Technology (MEXT) should play an active role in collaborating with the international research community to achieve the global accelerator program. This collaboration should utilize the framework of the Liaison Committee on Future High-Performance Accelerators, in partnership with the Cabinet Office, as well as other relevant ministries and agencies. The Reference Design Report estimated

15423-561: The effect of nonlinearity in optical materials (e.g. in second-harmonic generation , parametric down-conversion , optical parametric oscillators and the like). Unlike the giant pulse of a Q-switched laser, consecutive pulses from a mode-locked laser are phase-coherent; that is, the pulses (and not just their envelopes ) are identical and perfectly periodic. For this reason, and the extremely large peak powers attained by such short pulses, such lasers are invaluable in certain areas of research. Another method of achieving pulsed laser operation

15582-427: The effects of quantum mechanics ; in reality, the so-called classical electron radius has little to do with the true fundamental structure of the electron. There are elementary particles that spontaneously decay into less massive particles. An example is the muon , with a mean lifetime of 2.2 × 10  seconds, which decays into an electron, a muon neutrino and an electron antineutrino . The electron, on

15741-454: The electron from the Bohr magneton (the anomalous magnetic moment ). The extraordinarily precise agreement of this predicted difference with the experimentally determined value is viewed as one of the great achievements of quantum electrodynamics . The apparent paradox in classical physics of a point particle electron having intrinsic angular momentum and magnetic moment can be explained by

15900-560: The electron has an intrinsic magnetic moment along its spin axis. It is approximately equal to one Bohr magneton , which is a physical constant that is equal to 9.274 010 0657 (29) × 10  J⋅T . The orientation of the spin with respect to the momentum of the electron defines the property of elementary particles known as helicity . The electron has no known substructure . Nevertheless, in condensed matter physics , spin–charge separation can occur in some materials. In such cases, electrons 'split' into three independent particles,

16059-456: The energy states of an electron in a hydrogen atom that were equivalent to those that had been derived first by Bohr in 1913, and that were known to reproduce the hydrogen spectrum. Once spin and the interaction between multiple electrons were describable, quantum mechanics made it possible to predict the configuration of electrons in atoms with atomic numbers greater than hydrogen. In 1928, building on Wolfgang Pauli's work, Paul Dirac produced

16218-552: The first demonstration of stimulated emission. In 1950, Alfred Kastler (Nobel Prize for Physics 1966) proposed the method of optical pumping , which was experimentally demonstrated two years later by Brossel, Kastler, and Winter. In 1951, Joseph Weber submitted a paper on using stimulated emissions to make a microwave amplifier to the June 1952 Institute of Radio Engineers Vacuum Tube Research Conference in Ottawa , Ontario, Canada. After this presentation, RCA asked Weber to give

16377-448: The first high-energy particle collider was ADONE , which began operations in 1968. This device accelerated electrons and positrons in opposite directions, effectively doubling the energy of their collision when compared to striking a static target with an electron. The Large Electron–Positron Collider (LEP) at CERN , which was operational from 1989 to 2000, achieved collision energies of 209 GeV and made important measurements for

16536-406: The formation of virtual photons in the electric field generated by the electron. These photons can heuristically be thought of as causing the electron to shift about in a jittery fashion (known as zitterbewegung ), which results in a net circular motion with precession . This motion produces both the spin and the magnetic moment of the electron. In atoms, this creation of virtual photons explains

16695-568: The full explanation of the electron-pair formation and chemical bonding in terms of quantum mechanics . In 1919, the American chemist Irving Langmuir elaborated on the Lewis's static model of the atom and suggested that all electrons were distributed in successive "concentric (nearly) spherical shells, all of equal thickness". In turn, he divided the shells into a number of cells each of which contained one pair of electrons. With this model Langmuir

16854-421: The hydrogen atom, which should have the same energy, were shifted in relation to each other; the difference came to be called the Lamb shift . About the same time, Polykarp Kusch , working with Henry M. Foley , discovered the magnetic moment of the electron is slightly larger than predicted by Dirac's theory. This small difference was later called anomalous magnetic dipole moment of the electron. This difference

17013-422: The laser power inside the cavity; this equilibrium determines the operating point of the laser. If the applied pump power is too small, the gain will never be sufficient to overcome the cavity losses, and laser light will not be produced. The minimum pump power needed to begin laser action is called the lasing threshold . The gain medium will amplify any photons passing through it, regardless of direction; but only

17172-501: The lasing medium or pumping mechanism, then it is still classified as a "modulated" or "pulsed" continuous wave laser. Most laser diodes used in communication systems fall into that category. Some applications of lasers depend on a beam whose output power is constant over time. Such a laser is known as a continuous-wave ( CW ) laser. Many types of lasers can be made to operate in continuous-wave mode to satisfy such an application. Many of these lasers lase in several longitudinal modes at

17331-414: The latter case, the photon is emitted in the same direction as the light that is passing by. When the number of particles in one excited state exceeds the number of particles in some lower-energy state, population inversion is achieved. In this state, the rate of stimulated emission is larger than the rate of absorption of light in the medium, and therefore the light is amplified. A system with this property

17490-409: The light and free electrons is called Thomson scattering or linear Thomson scattering. Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation . The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation . The first laser

17649-509: The linewidth of light emitted from the passive resonator. Some lasers use a separate injection seeder to start the process off with a beam that is already highly coherent. This can produce beams with a narrower spectrum than would otherwise be possible. In 1963, Roy J. Glauber showed that coherent states are formed from combinations of photon number states, for which he was awarded the Nobel Prize in physics . A coherent beam of light

17808-402: The literal cavity that would be employed at microwave frequencies in a maser . The resonator typically consists of two mirrors between which a coherent beam of light travels in both directions, reflecting on itself so that an average photon will pass through the gain medium repeatedly before it is emitted from the output aperture or lost to diffraction or absorption. If the gain (amplification) in

17967-522: The lower level, emitting a new photon. The emitted photon exactly matches the original photon in wavelength, phase, and direction. This process is called stimulated emission. The gain medium is put into an excited state by an external source of energy. In most lasers, this medium consists of a population of atoms that have been excited into such a state using an outside light source, or an electrical field that supplies energy for atoms to absorb and be transformed into their excited states. The gain medium of

18126-489: The magnetic field and the electron velocity. This centripetal force causes the electron to follow a helical trajectory through the field at a radius called the gyroradius . The acceleration from this curving motion induces the electron to radiate energy in the form of synchrotron radiation. The energy emission in turn causes a recoil of the electron, known as the Abraham–Lorentz–Dirac Force , which creates

18285-516: The magnetic field that drives an electric motor . The electromagnetic field of an arbitrary moving charged particle is expressed by the Liénard–Wiechert potentials , which are valid even when the particle's speed is close to that of light ( relativistic ). When an electron is moving through a magnetic field, it is subject to the Lorentz force that acts perpendicularly to the plane defined by

18444-412: The maximum possible level, the introduced loss mechanism (often an electro- or acousto-optical element) is rapidly removed (or that occurs by itself in a passive device), allowing lasing to begin which rapidly obtains the stored energy in the gain medium. This results in a short pulse incorporating that energy, and thus a high peak power. A mode-locked laser is capable of emitting extremely short pulses on

18603-498: The medium is larger than the resonator losses, then the power of the recirculating light can rise exponentially . But each stimulated emission event returns an atom from its excited state to the ground state, reducing the gain of the medium. With increasing beam power, the net gain (gain minus loss) reduces to unity and the gain medium is said to be saturated. In a continuous wave (CW) laser, the balance of pump power against gain saturation and cavity losses produces an equilibrium value of

18762-564: The needs for the ILC. But all three were more or less well suited for housing a Linear Collider and one had ample choice for a site selection process in Europe. Outside Europe a number of countries expressed interest. Japan receives a large amount of funding for neutrino activities, such as the T2K experiment , a factor not in its favor, although 20 huge caverns with access tunnels have already been constructed in Japan for hydroelectric power plants (e.g.

18921-426: The negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal. Thomson measured m / e for cathode ray "corpuscles", and made good estimates of the charge e , leading to value for the mass m , finding a value 1400 times less massive than the least massive ion known: hydrogen. In the same year Emil Wiechert and Walter Kaufmann also calculated

19080-423: The nominal collision energy at the LHC will be higher than the ILC collision energy (14,000  GeV for the LHC vs. ~500 GeV for the ILC), measurements could be made more accurately at the ILC. Collisions between electrons and positrons are much simpler to analyze than collisions in which the energy is distributed among the constituent quarks , antiquarks and gluons of baryonic particles. As such, one of

19239-404: The object is not random, however: it is stored by atoms and molecules in " excited states ", which release photons with distinct wavelengths. This gives rise to the science of spectroscopy , which allows materials to be determined through the specific wavelengths that they emit. The underlying physical process creating photons in a laser is the same as in thermal radiation, but the actual emission

19398-1001: The observer will observe it to generate a magnetic field . Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law . Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications, such as tribology or frictional charging, electrolysis, electrochemistry, battery technologies, electronics , welding , cathode-ray tubes , photoelectricity, photovoltaic solar panels, electron microscopes , radiation therapy , lasers , gaseous ionization detectors , and particle accelerators . Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics . The Coulomb force interaction between

19557-456: The order of tens of picoseconds down to less than 10  femtoseconds . These pulses repeat at the round-trip time, that is, the time that it takes light to complete one round trip between the mirrors comprising the resonator. Due to the Fourier limit (also known as energy–time uncertainty ), a pulse of such short temporal length has a spectrum spread over a considerable bandwidth. Thus such

19716-430: The other hand, is thought to be stable on theoretical grounds: the electron is the least massive particle with non-zero electric charge, so its decay would violate charge conservation . The experimental lower bound for the electron's mean lifetime is 6.6 × 10 years, at a 90% confidence level . As with all particles, electrons can act as waves. This is called the wave–particle duality and can be demonstrated using

19875-405: The particle bunches will be sent to the superconducting radio frequency main linacs, each 11 km long, where they will be accelerated to 250 GeV. At this energy each beam will have an average power of about 5.3 megawatts . Five bunch trains will be produced and accelerated per second. To maintain a sufficient luminosity to produce results in a reasonable time frame after acceleration

20034-551: The photon, have symmetric wave functions instead. In the case of antisymmetry, solutions of the wave equation for interacting electrons result in a zero probability that each pair will occupy the same location or state. This is responsible for the Pauli exclusion principle , which precludes any two electrons from occupying the same quantum state. This principle explains many of the properties of electrons. For example, it causes groups of bound electrons to occupy different orbitals in an atom, rather than all overlapping each other in

20193-418: The photons in a spatial mode supported by the resonator will pass more than once through the medium and receive substantial amplification. In most lasers, lasing begins with spontaneous emission into the lasing mode. This initial light is then amplified by stimulated emission in the gain medium. Stimulated emission produces light that matches the input signal in direction, wavelength, and polarization, whereas

20352-456: The positive protons within atomic nuclei and the negative electrons without allows the composition of the two known as atoms . Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding . In 1838, British natural philosopher Richard Laming first hypothesized

20511-452: The positron is symbolized by e . The electron has an intrinsic angular momentum or spin of ⁠ ħ / 2 ⁠ . This property is usually stated by referring to the electron as a spin-1/2 particle. For such particles the spin magnitude is ⁠ ħ / 2 ⁠ , while the result of the measurement of a projection of the spin on any axis can only be ± ⁠ ħ / 2 ⁠ . In addition to spin,

20670-409: The power output is essentially continuous over time or whether its output takes the form of pulses of light on one or another time scale. Of course, even a laser whose output is normally continuous can be intentionally turned on and off at some rate to create pulses of light. When the modulation rate is on time scales much slower than the cavity lifetime and the period over which energy can be stored in

20829-662: The properties of the emitted light, such as the polarization, wavelength, and shape of the beam. Electrons and how they interact with electromagnetic fields are important in our understanding of chemistry and physics . In the classical view , the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom . However, quantum mechanical effects force electrons to take on discrete positions in orbitals . Thus, electrons are found in specific energy levels of an atom, two of which are shown below: An electron in an atom can absorb energy from light ( photons ) or heat ( phonons ) only if there

20988-403: The rays carried negative charge. By measuring the amount of deflection for a given electric and magnetic field , in 1890 Schuster was able to estimate the charge-to-mass ratio of the ray components. However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time. This is because it was assumed that

21147-457: The relationship between the A coefficient , describing spontaneous emission, and the B coefficient which applies to absorption and stimulated emission. In the case of the free electron laser , atomic energy levels are not involved; it appears that the operation of this rather exotic device can be explained without reference to quantum mechanics . A laser can be classified as operating in either continuous or pulsed mode, depending on whether

21306-519: The roles of the ILC would be making precision measurements of the properties of particles discovered at the LHC. It is widely expected that effects of physics beyond that described in the current Standard Model will be detected by experiments at the proposed ILC. In addition, particles and interactions described by the Standard Model are expected to be discovered and measured. At the ILC physicists hope to be able to: To achieve these goals, new generation particle detectors are necessary. In August 2004,

21465-455: The same conclusion. A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess (+) or deficit (−). He gave them the modern charge nomenclature of positive and negative respectively. Franklin thought of the charge carrier as being positive, but he did not correctly identify which situation was

21624-423: The same orbit. In a simplified picture, which often tends to give the wrong idea but may serve to illustrate some aspects, every photon spends some time as a combination of a virtual electron plus its antiparticle, the virtual positron, which rapidly annihilate each other shortly thereafter. The combination of the energy variation needed to create these particles, and the time during which they exist, fall under

21783-410: The same time, and beats between the slightly different optical frequencies of those oscillations will produce amplitude variations on time scales shorter than the round-trip time (the reciprocal of the frequency spacing between modes), typically a few nanoseconds or less. In most cases, these lasers are still termed "continuous-wave" as their output power is steady when averaged over longer periods, with

21942-489: The single particle formalism, by replacing its mass with the effective mass tensor . In the Standard Model of particle physics, electrons belong to the group of subatomic particles called leptons , which are believed to be fundamental or elementary particles . Electrons have the lowest mass of any charged lepton (or electrically charged particle of any type) and belong to the first generation of fundamental particles. The second and third generation contain charged leptons,

22101-435: The state of the system. The wave function of fermions, including electrons, is antisymmetric, meaning that it changes sign when two electrons are swapped; that is, ψ ( r 1 , r 2 ) = − ψ ( r 2 , r 1 ) , where the variables r 1 and r 2 correspond to the first and second electrons, respectively. Since the absolute value is not changed by a sign swap, this corresponds to equal probabilities. Bosons , such as

22260-484: The structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. In 1913, Danish physicist Niels Bohr postulated that electrons resided in quantized energy states, with their energies determined by the angular momentum of the electron's orbit about the nucleus. The electrons could move between those states, or orbits, by the emission or absorption of photons of specific frequencies. By means of these quantized orbits, he accurately explained

22419-504: The subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta , on the basis of their ability to penetrate matter. In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for cathode rays. This evidence strengthened

22578-423: The term electrolion in 1881. Ten years later, he switched to electron to describe these elementary charges, writing in 1894: "... an estimate was made of the actual amount of this most remarkable fundamental unit of electricity, for which I have since ventured to suggest the name electron ". A 1906 proposal to change to electrion failed because Hendrik Lorentz preferred to keep electron . The word electron

22737-522: The threshold of detectability expressed by the Heisenberg uncertainty relation , Δ E  · Δ t  ≥  ħ . In effect, the energy needed to create these virtual particles, Δ E , can be "borrowed" from the vacuum for a period of time, Δ t , so that their product is no more than the reduced Planck constant , ħ ≈ 6.6 × 10  eV·s . Thus, for a virtual electron, Δ t is at most 1.3 × 10  s . While an electron–positron virtual pair

22896-573: The total cost to be US$ 25 billion. ILC Director Barish said this is likely to be an overestimate. Other Department of Energy officials have estimated a $ 20 billion total. Upon completion of the 2013 ILC Design Report, Barish said the cost of building the ILC was the equivalent of 7.78 billion 2012 U.S. dollars; it will require "22.6 million hours of labor and location-specific costs including site preparation, scientific detectors and facility operations." Electron The electron ( e , or β in nuclear reactions)

23055-425: The two mirrors, the output coupler , is partially transparent. Some of the light escapes through this mirror. Depending on the design of the cavity (whether the mirrors are flat or curved ), the light coming out of the laser may spread out or form a narrow beam . In analogy to electronic oscillators , this device is sometimes called a laser oscillator . Most practical lasers contain additional elements that affect

23214-426: The upper limit of the particle's radius to be 10  meters. The upper bound of the electron radius of 10  meters can be derived using the uncertainty relation in energy. There is also a physical constant called the " classical electron radius ", with the much larger value of 2.8179 × 10  m , greater than the radius of the proton. However, the terminology comes from a simplistic calculation that ignores

23373-410: The very high-frequency power variations having little or no impact on the intended application. (However, the term is not applied to mode-locked lasers, where the intention is to create very short pulses at the rate of the round-trip time.) For continuous-wave operation, the population inversion of the gain medium needs to be continually replenished by a steady pump source. In some lasing media, this

23532-487: The view that electrons existed as components of atoms. In 1897, the British physicist J. J. Thomson , with his colleagues John S. Townsend and H. A. Wilson , performed experiments indicating that cathode rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. By 1899 he showed that their charge-to-mass ratio, e / m , was independent of cathode material. He further showed that

23691-473: The wavelength of the photon by an amount called the Compton shift . The maximum magnitude of this wavelength shift is h / m e c , which is known as the Compton wavelength . For an electron, it has a value of 2.43 × 10  m . When the wavelength of the light is long (for instance, the wavelength of the visible light is 0.4–0.7 μm) the wavelength shift becomes negligible. Such interaction between

23850-563: Was Thomson's graduate student, performed the first experiments but he died soon after in a motorcycle accident and is rarely mentioned. De Broglie's prediction of a wave nature for electrons led Erwin Schrödinger to postulate a wave equation for electrons moving under the influence of the nucleus in the atom. In 1926, this equation, the Schrödinger equation , successfully described how electron waves propagated. Rather than yielding

24009-416: Was able to qualitatively explain the chemical properties of all elements in the periodic table, which were known to largely repeat themselves according to the periodic law . In 1924, Austrian physicist Wolfgang Pauli observed that the shell-like structure of the atom could be explained by a set of four parameters that defined every quantum energy state, as long as each state was occupied by no more than

24168-421: Was built in 1960 by Theodore Maiman at Hughes Research Laboratories , based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow . A laser differs from other sources of light in that it emits light that is coherent . Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as optical communication, laser cutting , and lithography . It also allows

24327-598: Was called a maser , for "microwave amplification by stimulated emission of radiation". When similar optical devices were developed they were first called optical masers , until "microwave" was replaced by "light" in the acronym, to become laser . Today, all such devices operating at frequencies higher than microwaves (approximately above 300 GHz ) are called lasers (e.g. infrared lasers , ultraviolet lasers , X-ray lasers , gamma-ray lasers ), whereas devices operating at microwave or lower radio frequencies are called masers. The back-formed verb " to lase "

24486-734: Was caused by the rays striking the tube walls. Furthermore, he also discovered that these rays are deflected by magnets just like lines of current. In 1876, the German physicist Eugen Goldstein showed that the rays were emitted perpendicular to the cathode surface, which distinguished between the rays that were emitted from the cathode and the incandescent light. Goldstein dubbed the rays cathode rays . Decades of experimental and theoretical research involving cathode rays were important in J. J. Thomson 's eventual discovery of electrons. Goldstein also experimented with double cathodes and hypothesized that one ray may repulse another, although he didn't believe that any particles might be involved. During

24645-600: Was considered favorable for a number of practical reasons but due to the LHC the site was disfavored. At DESY in Hamburg the tunnel is close to the surface in water saturated soil. Germany leads Europe for scientific funding and was therefore considered reliable in terms of funding. At JINR in Dubna the tunnel is close to the surface in non-permeable soil. Dubna has a pre-accelerator complex which could have been easily adapted for

24804-672: Was governed by the inverse square law . After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion . He was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis . However, Stoney believed these charges were permanently attached to atoms and could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity". Stoney initially coined

24963-426: Was later explained by the theory of quantum electrodynamics , developed by Sin-Itiro Tomonaga , Julian Schwinger and Richard Feynman in the late 1940s. With the development of the particle accelerator during the first half of the twentieth century, physicists began to delve deeper into the properties of subatomic particles . The first successful attempt to accelerate electrons using electromagnetic induction

25122-415: Was made in 1942 by Donald Kerst . His initial betatron reached energies of 2.3 MeV, while subsequent betatrons achieved 300 MeV. In 1947, synchrotron radiation was discovered with a 70 MeV electron synchrotron at General Electric . This radiation was caused by the acceleration of electrons through a magnetic field as they moved near the speed of light. With a beam energy of 1.5 GeV,

25281-413: Was originally coined by George Johnstone Stoney in 1891 as a tentative name for the basic unit of electrical charge (which had then yet to be discovered). The electron's charge was more carefully measured by the American physicists Robert Millikan and Harvey Fletcher in their oil-drop experiment of 1909, the results of which were published in 1911. This experiment used an electric field to prevent

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