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Multipactor
The multipactor effect is a phenomenon in radio-frequency (RF) amplifier vacuum tubes and waveguides, where, under certain conditions, secondary electron emission in resonance with an alternating electromagnetic field leads to exponential electron multiplication, possibly damaging and even destroying the RF device. Description The multipactor effect occurs when electrons accelerated by radio-frequency (RF) fields are self-sustained in a vacuum (or near vacuum) via an electron avalanche caused by secondary electron emission. Valery D. Shemelin and Sergey A. Belomestnykh, Multipactor in Accelerating Cavities (Book 1 of a Series: Particle Acceleration and Detection) 1st ed. ISSN 1611-1052, Springer Nature Switzerland AG, 2020 The impact of an electron to a surface can, depending on its energy and angle, release one or more secondary electrons into the vacuum. These electrons can then be accelerated by the RF fields and impact with the same or another surface. Should the impact energ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fusor
A fusor is a device that uses an electric field to heat ions to a temperature at which they undergo nuclear fusion. The machine induces a potential difference between two metal cages, inside a vacuum. Positive ions fall down this voltage drop, building up speed. If they collide in the center, they can fuse. This is one kind of an inertial electrostatic confinement device – a branch of fusion research. A Farnsworth–Hirsch fusor is the most common type of fusor. This design came from work by Philo T. Farnsworth in 1964 and Robert L. Hirsch in 1967.Robert L. Hirsch, "Inertial-Electrostatic Confinement of Ionized Fusion Gases", Journal of Applied Physics, v. 38, no. 7, October 1967 A variant type of fusor had been proposed previously by William Elmore, James L. Tuck, and Ken Watson at the Los Alamos National Laboratory"On the Inertial Electrostatic Confinement of a Plasma" William Elmore, James Tuck and Ken Watson, The Physics of Fluids, January 30, 1959 though they never bui ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philo Farnsworth
Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971), "The father of television", was the American inventor and pioneer who was granted the first patent for the television by the United States Government. Burns, R. W. (1998), ''Television: An international history of the formative years''. IET History of Technology Series, 22. LondonThe Institution of Engineering and Technology (IET) p. 370. . He also invented a video camera tube, and the image dissector. He commercially produced and sold a fully functioning television system, complete with receiver and camera—which he produced commercially through the Farnsworth Television and Radio Corporation from 1938 to 1951, in Fort Wayne, Indiana. In later life, Farnsworth invented a small nuclear fusion device, the Farnsworth Fusor, employing inertial electrostatic confinement (IEC). Like many fusion devices, it was not a practical device for generating nuclear power, although it provides a viable source of neutrons. The desi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental research in particle physics. Accelerators are also used as synchrotron light sources for the study of condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including particle therapy for oncology, oncological purposes, Isotopes in medicine, radioisotope production for medical diagnostics, Ion implantation, ion implanters for the manufacturing of Semiconductor, semiconductors, and Accelerator mass spectrometry, accelerator mass spectrometers for measurements of rare isotopes such as radiocarbon. Large accelerators include the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in New York, and the largest accelerator, the Large Hadron Collider near Geneva, Switzerland, operated b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accelerator Physics
Accelerator physics is a branch of applied physics, concerned with designing, building and operating particle accelerators. As such, it can be described as the study of motion, manipulation and observation of relativistic charged particle beams and their interaction with accelerator structures by electromagnetic fields. It is also related to other fields: * Microwave engineering (for acceleration/deflection structures in the radio frequency range). *Optics with an emphasis on geometrical optics (beam focusing and bending) and laser physics (laser-particle interaction). * Computer technology with an emphasis on digital signal processing; e.g., for automated manipulation of the particle beam. * Plasma physics, for the description of intense beams. The experiments conducted with particle accelerators are not regarded as part of accelerator physics, but belong (according to the objectives of the experiments) to, e.g., particle physics, nuclear physics, condensed matter physics or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1924 In Science
The year 1924 in science and technology involved some significant events, listed below. Astronomy and space exploration * November 23 – Edwin Hubble announces his discovery that Andromeda, previously believed to be a nebula, is actually another galaxy, and that the Milky Way is only one of many such galaxies in the universe. * The Einstein Tower near Potsdam, Germany, designed by Erich Mendelsohn, becomes operational as an astrophysical observatory. * Mount Stromlo Observatory near Canberra, Australia, is established as the Commonwealth Solar Observatory. * 1056 Azalea is discovered. Biology *The term " ectogenesis" is coined by British scientist J. B. S. Haldane to describe the growth of mammalian embryos in artificial environments. *California grizzly bear last sighted. Biochemistry * The first inactive tetanus vaccine (tetanus toxoid, TT) is discovered by Gaston Ramon, C. Zoeller and P. Descombey and produced. * The first scarlet fever vaccine is discovered by Georg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1924 Introductions
Nineteen or 19 may refer to: * 19 (number) * One of the years 19 BC, AD 19, 1919, 2019 Films * ''19'' (film), a 2001 Japanese film * ''Nineteen'' (1987 film), a 1987 science fiction film * '' 19-Nineteen'', a 2009 South Korean film * '' Diciannove'', a 2024 Italian drama film informally referred to as "Nineteen" in some sources Science * Potassium, an alkali metal * 19 Fortuna, an asteroid Music * 19 (band), a Japanese pop music duo Albums * ''19'' (Adele album), 2008 * ''19'', a 2003 album by Alsou * ''19'', a 2006 album by Evan Yo * ''19'', a 2018 album by MHD * ''19'', one half of the double album '' 63/19'' by Kool A.D. * ''Number Nineteen'', a 1971 album by American jazz pianist Mal Waldron * ''XIX'' (EP), a 2019 EP by 1the9 Songs * "19" (song), a 1985 song by British musician Paul Hardcastle * "Stone in Focus", officially "#19", a composition by Aphex Twin * "Nineteen", a song from the 1992 album ''Refugee'' by Bad4Good * "Nineteen", a song from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Avalanche
An electron avalanche is a process in which a number of free electrons in a transmission medium are subjected to strong acceleration by an electric field and subsequently collide with other atoms of the medium, thereby ionizing them ( impact ionization). This releases additional electrons which accelerate and collide with further atoms, releasing more electrons—a chain reaction. In a gas, this causes the affected region to become an electrically conductive plasma. The avalanche effect was discovered by John Sealy Townsend in his work between 1897 and 1901, and is also known as the Townsend discharge. Electron avalanches are essential to the dielectric breakdown process within gases. The process can culminate in corona discharges, streamers, leaders, or in a spark or continuous arc that completely bridges the gap between the electrical conductors that are applying the voltage. The process extends to huge sparks — streamers in lightning discharges propagate by forma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capacitively Coupled Plasma
A capacitively coupled plasma (CCP) is one of the most common types of industrial plasma sources. It essentially consists of two metal electrodes separated by a small distance, placed in a reactor. The gas pressure in the reactor can be lower than atmosphere or it can be atmospheric. Description A typical CCP system is driven by a single radio-frequency (RF) power supply, typically at 13.56 MHz.UK Wireless Telegraphy (Short Range Devices) (Exemption) Regulations 199/ref> One of two electrodes is connected to the power supply, and the other one is ground (electricity), grounded. As this configuration is similar in principle to a capacitor in an electric circuit, the plasma formed in this configuration is called a capacitively coupled plasma. When an electric field is generated between electrodes, atoms are ionized and release electrons. The electrons in the gas are accelerated by the RF field and can ionize the gas directly or indirectly by collisions, producing secondar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an Insulator (electricity), electrical insulator that can be Polarisability, polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of Polarisation density, dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly Chemical bond, bonded molecules, those molecules not only become polarised, but also reorient so that their Symmetry axis, symmetry axes a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Communication
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently. The radio waves used for telecommunications links travel by line of sight and so are obstructed by the curve of the Earth. The purpose of communications satellites is to rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
