Brewster's angle is an angle of incidence at which light with a particular polarization is transmitted through a transparent dielectric surface, with no reflection. When unpolarized light is incident at this angle, the light, reflected from the surface is therefore polarized; this special angle of incidence is named after the Scottish physicist Sir David Brewster. When light encounters a boundary between two media with different refractive indices, some of it is reflected as shown in the figure above; the fraction, reflected is described by the Fresnel equations, is dependent upon the incoming light's polarization and angle of incidence. The Fresnel equations predict that light with the p polarization will not be reflected if the angle of incidence is θ B = arctan, where n1 is the refractive index of the initial medium through which the light propagates, n2 is the index of the other medium; this equation is known as Brewster's law, the angle defined by it is Brewster's angle. The physical mechanism for this can be qualitatively understood from the manner in which electric dipoles in the media respond to p-polarized light.
One can imagine that light incident on the surface is absorbed, re-radiated by oscillating electric dipoles at the interface between the two media. The polarization of propagating light is always perpendicular to the direction in which the light is travelling; the dipoles that produce the transmitted light oscillate in the polarization direction of that light. These same oscillating dipoles generate the reflected light. However, dipoles do not radiate any energy in the direction of the dipole moment. If the refracted light is p-polarized and propagates perpendicular to the direction in which the light is predicted to be specularly reflected, the dipoles point along the specular reflection direction and therefore no light can be reflected. With simple geometry this condition can be expressed as θ 1 + θ 2 = 90 ∘, where θ1 is the angle of reflection and θ2 is the angle of refraction. Using Snell's law, n 1 sin θ 1 = n 2 sin θ 2, one can calculate the incident angle θ1 = θB at which no light is reflected: n 1 sin θ B = n 2 sin = n 2 cos θ B.
Solving for θB gives θ B = arctan. For a glass medium in air, Brewster's angle for visible light is 56°, while for an air-water interface, it is 53°. Since the refractive index for a given medium changes depending on the wavelength of light, Brewster's angle will vary with wavelength; the phenomenon of light being polarized by reflection from a surface at a particular angle was first observed by Étienne-Louis Malus in 1808. He attempted to relate the polarizing angle to the refractive index of the material, but was frustrated by the inconsistent quality of glasses available at that time. In 1815, Brewster experimented with higher-quality materials and showed that this angle was a function of the refractive index, defining Brewster's law. Brewster's angle is referred to as the "polarizing angle", because light that reflects from a surface at this angle is polarized perpendicular to the plane of incidence. A glass plate or a stack of plates placed at Brewster's angle in a light beam can, thus, be used as a polarizer.
The concept of a polarizing angle can be extended to the concept of a Brewster wavenumber to cover planar interfaces between two linear bianisotropic materials. In the case of reflection at Brewster's angle, the reflected and refracted rays are mutually perpendicular. For magnetic materials, Brewster's angle can exist for only one of the incident wave polarizations, as determined by the relative strengths of the dielectric permittivity and magnetic permeability; this has implications for the existence of generalized Brewster angles for dielectric metasurfaces. Polarized sunglasses use the principle of Brewster's angle to reduce glare from the sun reflecting off horizontal surfaces such as water or road. In a large range of angles around Brewster's angle, the reflection of p-polarized light is lower than s-polarized light. Thus, if the sun is low in the sky, reflected light is s-polarized. Polarizing sunglasses use a polarizing material such as Polaroid sheets to block horizontally-polarized light, preferentially blocking reflections from horizontal surfaces.
The effect is stro
Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory is a federal research facility in Livermore, United States, founded by the University of California, Berkeley in 1952. A Federally Funded Research and Development Center, it is funded by the U. S. Department of Energy and managed and operated by Lawrence Livermore National Security, LLC, a partnership of the University of California, Bechtel, BWX Technologies, AECOM, Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium named after it. LLNL is self-described as "a premier research and development institution for science and technology applied to national security." Its principal responsibility is ensuring the safety and reliability of the nation's nuclear weapons through the application of advanced science and technology. The Laboratory applies its special expertise and multidisciplinary capabilities to preventing the proliferation and use of weapons of mass destruction, bolstering homeland security and solving other nationally important problems, including energy and environmental security, basic science and economic competitiveness.
The Laboratory is located on a one-square-mile site at the eastern edge of Livermore. It operates a 7,000 acres remote experimental test site, called Site 300, situated about 15 miles southeast of the main lab site. LLNL has an annual budget of about $1.5 billion and a staff of 5,800 employees. LLNL was established in 1952 as the University of California Radiation Laboratory at Livermore, an offshoot of the existing UC Radiation Laboratory at Berkeley, it was intended to spur innovation and provide competition to the nuclear weapon design laboratory at Los Alamos in New Mexico, home of the Manhattan Project that developed the first atomic weapons. Edward Teller and Ernest Lawrence, director of the Radiation Laboratory at Berkeley, are regarded as the co-founders of the Livermore facility; the new laboratory was sited at a former naval air station of World War II. It was home to several UC Radiation Laboratory projects that were too large for its location in the Berkeley Hills above the UC campus, including one of the first experiments in the magnetic approach to confined thermonuclear reactions.
About half an hour southeast of Berkeley, the Livermore site provided much greater security for classified projects than an urban university campus. Lawrence tapped age 32, to run Livermore. Under York, the Lab had four main programs: Project Sherwood, Project Whitney, diagnostic weapon experiments, a basic physics program. York and the new lab embraced the Lawrence "big science" approach, tackling challenging projects with physicists, chemists and computational scientists working together in multidisciplinary teams. Lawrence died in August 1958 and shortly after, the university's board of regents named both laboratories for him, as the Lawrence Radiation Laboratory; the Berkeley and Livermore laboratories have had close relationships on research projects, business operations, staff. The Livermore Lab was established as a branch of the Berkeley laboratory; the Livermore lab was not severed administratively from the Berkeley lab until 1971. To this day, in official planning documents and records, Lawrence Berkeley National Laboratory is designated as Site 100, Lawrence Livermore National Lab as Site 200, LLNL's remote test location as Site 300.
The laboratory was renamed Lawrence Livermore Laboratory in 1971. On October 1, 2007 LLNS assumed management of LLNL from the University of California, which had managed and operated the Laboratory since its inception 55 years before; the laboratory was honored in 2012 by having the synthetic chemical element livermorium named after it. The LLNS takeover of the laboratory has been controversial. In May 2013, an Alameda County jury awarded over $2.7 million to five former laboratory employees who were among 430 employees LLNS laid off during 2008. The jury found that LLNS breached a contractual obligation to terminate the employees only for "reasonable cause." The five plaintiffs have pending age discrimination claims against LLNS, which will be heard by a different jury in a separate trial. There are 125 co-plaintiffs awaiting trial on similar claims against LLNS; the May 2008 layoff was the first layoff at the laboratory in nearly 40 years. On March 14, 2011, the City of Livermore expanded the city's boundaries to annex LLNL and move it within the city limits.
The unanimous vote by the Livermore city council expanded Livermore's southeastern boundaries to cover 15 land parcels covering 1,057 acres that comprise the LLNL site. The site was an unincorporated area of Alameda County; the LLNL campus continues to be owned by the federal government. From its inception, Livermore focused on new weapon design concepts; the lab persevered and its subsequent designs proved successful. In 1957, the Livermore Lab was selected to develop the warhead for the Navy's Polaris missile; this warhead required numerous innovations to fit a nuclear warhead into the small confines of the missile nosecone. During the Cold War, many Livermore-designed warheads entered service; these were used in missiles ranging in size from the Lance surface-to-surface tactical missile to the megaton-class Spartan antiballistic missile. Over the years, LLNL designed the following warheads: W27 (Regulus cruise missile.
Shiva Star just SHIVA, is a high-powered pulsed-power research device located at the Air Force Research Laboratory on the Kirtland Air Force Base in Albuquerque, New Mexico. The device was built in the 1970s for high-power X-ray research, was re-directed to studies for the Strategic Defense Initiative, is now being used for magnetized target fusion research. Shiva Star was named after the Hindu god Shiva because its prototype had four "arms". Research at Princeton University in using Z-Pinch devices as a potential space propulsion device led to the exploration of the resulting x-ray production; this led directly to the original SHIVA effort in 1971. In these experiments a thin foil of a "high-Z" metal was compressed magnetically by dumping the output of capacitor banks into magnetic coils; as it was first built in 1974, SHIVA I consisted of four banks of capacitors arranged in a cross shape with the experimental chamber in the middle. The capacitors held 1 MJ at 100 kV. Early experiments were hampered by problems with the implosion, but by 1976 successful implosions were being carried out.
The capacitor banks were upgraded to 1.9 MJ at 120 kV in 1979, becoming Shiva II. Another upgrade followed in 1982, adding two more capacitor banks, thereby changing the shape from a cross to a star, resulting in the current Shiva Star device. Shiva Star was used as a dense plasma focus driver in the mid-80s, as an experimental magnetic driver for conventional projectiles in the late-80s. Shiva Star was used to develop an experimental weapon known as MARAUDER for the SDI effort between 1989 and 1995; the idea appears to have been to create compact toroids of high-density plasma that would be ejected from the device using a massive magnetic pulse. The plasma projectiles would be shot at a speed expected to be 3000 km/s in 1995 and 10,000 km/s by 2000. A shot has the energy of 5 pounds of TNT exploding. Doughnut-shaped rings of plasma and balls of lightning exploded with devastating thermal and mechanical effects when hitting their target and produced pulse of electromagnetic radiation that could scramble electronics, the energy would shower the interior of the target with high-energy x-rays that would destroy the electronics inside.
The tests cost a few million dollars a year. The project became classified, no information about the fate of the project has been published after 1995. Shiva Star was most revived for work in fusion research. A new technique, magnetized target fusion, compresses a small plasma load with an imploding metal foil. Shiva Star's 10 MJ capacitor banks were perfect for this role, starting in 2007 the new FRCHX experiment has been using Shiva Star with 1 mm thick aluminium foil, accelerated to about 5 km/s. Dresden High Magnetic Field Laboratory LINUS magnetized target fusion Nova
A nuclear reactor known as an atomic pile, is a device used to initiate and control a self-sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. Heat from nuclear fission is passed to a working fluid; these either turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating; some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. Some are run only for research; as of early 2019, the IAEA reports there are 454 nuclear power reactors and 226 nuclear research reactors in operation around the world. Just as conventional power-stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear reactors convert the energy released by controlled nuclear fission into thermal energy for further conversion to mechanical or electrical forms; when a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission.
The heavy nucleus splits into two or more lighter nuclei, releasing kinetic energy, gamma radiation, free neutrons. A portion of these neutrons may be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, so on; this is known as a nuclear chain reaction. To control such a nuclear chain reaction, neutron poisons and neutron moderators can change the portion of neutrons that will go on to cause more fission. Nuclear reactors have automatic and manual systems to shut the fission reaction down if monitoring detects unsafe conditions. Used moderators include regular water, solid graphite and heavy water; some experimental types of reactor have used beryllium, hydrocarbons have been suggested as another possibility. The reactor core generates heat in a number of ways: The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms; the reactor absorbs some of the gamma rays produced during fission and converts their energy into heat.
Heat is produced by the radioactive decay of fission products and materials that have been activated by neutron absorption. This decay heat-source will remain for some time after the reactor is shut down. A kilogram of uranium-235 converted via nuclear processes releases three million times more energy than a kilogram of coal burned conventionally. A nuclear reactor coolant — water but sometimes a gas or a liquid metal or molten salt — is circulated past the reactor core to absorb the heat that it generates; the heat is carried away from the reactor and is used to generate steam. Most reactor systems employ a cooling system, physically separated from the water that will be boiled to produce pressurized steam for the turbines, like the pressurized water reactor. However, in some reactors the water for the steam turbines is boiled directly by the reactor core; the rate of fission reactions within a reactor core can be adjusted by controlling the quantity of neutrons that are able to induce further fission events.
Nuclear reactors employ several methods of neutron control to adjust the reactor's power output. Some of these methods arising from the physics of radioactive decay and are accounted for during the reactor's operation, while others are mechanisms engineered into the reactor design for a distinct purpose; the fastest method for adjusting levels of fission-inducing neutrons in a reactor is via movement of the control rods. Control rods therefore tend to absorb neutrons; when a control rod is inserted deeper into the reactor, it absorbs more neutrons than the material it displaces—often the moderator. This action results in fewer neutrons available to cause fission and reduces the reactor's power output. Conversely, extracting the control rod will result in an increase in the rate of fission events and an increase in power; the physics of radioactive decay affects neutron populations in a reactor. One such process is delayed neutron emission by a number of neutron-rich fission isotopes; these delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder released upon fission.
The fission products which produce delayed neutrons have half lives for their decay by neutron emission that range from milliseconds to as long as several minutes, so considerable time is required to determine when a reactor reaches the critical point. Keeping the reactor in the zone of chain-reactivity where delayed neutrons are necessary to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; this last stage, where delayed neutrons are no longer required to maintain criticality, is known as the prompt critical point. There is a scale for describing criticality in numerical form, in which bare criticality is known as zero dollars and the prompt critical point is one dollar, other points in the process interpolated in cents. In some reactors, the coolant acts as a neutron moderator. A moderator increases the power of the reactor by causin
Laboratory for Laser Energetics
The Laboratory for Laser Energetics is a scientific research facility, part of the University of Rochester's south campus, located in Brighton, New York. The lab was established in 1970 and its operations since have been funded jointly; the Laser Lab was commissioned to serve as a center for investigations of high-energy physics those involving the interaction of intense laser radiation with matter. Many types of scientific experiments are performed at the facility with a strong emphasis on inertial confinement, direct drive, laser-induced fusion, fundamental plasma physics and astrophysics using OMEGA. In June of 1995, OMEGA became the world's highest-energy ultraviolet laser; the lab shares its building with the Center for Optoelectronics and Imaging and the Center for Optics Manufacturing. The Robert L. Sproull Center for Ultra High Intensity Laser Research was opened in 2005 and houses the OMEGA EP laser, completed in May 2008; the laboratory is unique in conducting big science on a university campus.
More than 180 Ph. D.s have been awarded for research done at the LLE. During summer months the lab sponsors a program for high school students which involves local-area high school juniors in the research being done at the laboratory. Most of the projects are done on current research, led by senior scientists at the lab; the LLE was founded on the University of Rochester's campus in 1970, by Dr. Moshe Lubin. Working with outside companies such as Kodak the team built Delta, a four beam laser system in 1972. Construction started on the current LLE site in 1976; the facility opened a six beam laser system in 1978 and followed with a 24 beam system two years later. In 2018, Donna Strickland and Gérard Mourou shared a Nobel prize for work they had undertaken in 1985 while at LLE, they invented a method to amplify laser pulses by "chirping" for which they would share the 2018 Nobel Prize in Physics. This method disperses a short, broadband pulse of laser light into a temporally longer spectrum of wavelengths.
The system amplifies the laser at each wavelength and reconstitutes the beam into one color. Chirp pulsed amplification became instrumental in building the National Ignition Facility and the Omega EP system. In 1995, the omega laser system was increased to 60 beams, in 2008 the Omega extended performance system was opened; the Guardian and Scientific American provided simplified summaries of the work of Strickland and Mourou: it "paved the way for the shortest, most intense laser beams created". "The ultrabrief, ultrasharp beams can be used to make precise cuts so their technique is now used in laser machining and enables doctors to perform millions of corrective" laser eye surgeries. The OMEGA laser at the LLE is one of the highest energy lasers in the world, it is a 60-beam ultraviolet frequency-tripled neodymium glass laser, capable of delivering 30 kilojoules at up to 60 terawatts onto a target less than 1 millimeter in diameter. Construction and commissioning of the laser were completed in 1995.
OMEGA held the record for highest energy laser from 1999 to 2005, when the first 8 beams of the National Ignition Facility exceeded OMEGA's output by about 30 kJ in the ultraviolet. The maximum fusion yield of OMEGA so far is about 1014 neutrons per shot, it once held the record for highest neutron yield of any inertial confinement fusion device; the four beam OMEGA EP laser system was dedicated on May 16, 2008. Along with four NIF-like laser beams, it hosts a new target chamber and a vacuum pulse compression chamber containing large-aperture pulse compression gratings, allowing the laser system to perform short pulse laser shots; the laser is housed inside a 2005 building addition. The combination of the OMEGA and the OMEGA EP laser systems make LLE the world's only integrated cryogenic fast ignition experimental facility. LLE is operated by the University of Rochester. Omega and Omega EP are user facilities. LLNL's principal sponsor is the Department of Energy/National Nuclear Security Administration Office of Defense Programs, which supports its stockpile stewardship and advanced scientific computing programs.
The Laboratory has a five-fold mission: To conduct implosion experiments and basic physics experiments in support of the National Inertial Confinement Fusion program. To develop new laser and materials technologies. To provide graduate and undergraduate education in electro-optics, high-power lasers, high-energy-density physics, plasma physics, nuclear fusion technology. To operate the National Laser Users' Facility. To conduct research and development in advanced technology related to high-energy-density phenomena. National Ignition Facility GEKKO XII Nike laser Laser Mégajoule HiPER Inertial confinement fusion University of Rochester Riccardo Betti Gérard Mourou Big Science Official website Center for Optics Manufacturing OMEGA OMEGA EP Omega Laser Facility Users' Guide This users’ guide was created to help users of the Omega Laser Facility propose and carry out experiments at the facility, it has extensive technical details on the facility. R. Stephen Craxton
Hinduism is an Indian religion and dharma, or way of life practised in the Indian subcontinent and parts of Southeast Asia. Hinduism has been called the oldest religion in the world, some practitioners and scholars refer to it as Sanātana Dharma, "the eternal tradition", or the "eternal way", beyond human history. Scholars regard Hinduism as a fusion or synthesis of various Indian cultures and traditions, with diverse roots and no founder; this "Hindu synthesis" started to develop between 500 BCE and 300 CE, after the end of the Vedic period, flourished in the medieval period, with the decline of Buddhism in India. Although Hinduism contains a broad range of philosophies, it is linked by shared concepts, recognisable rituals, shared textual resources, pilgrimage to sacred sites. Hindu texts are classified into Smṛti; these texts discuss theology, mythology, Vedic yajna, agamic rituals, temple building, among other topics. Major scriptures include the Vedas and Upanishads, the Bhagavad Gita, the Ramayana, the Āgamas.
Sources of authority and eternal truths in its texts play an important role, but there is a strong Hindu tradition of questioning authority in order to deepen the understanding of these truths and to further develop the tradition. Prominent themes in Hindu beliefs include the four Puruṣārthas, the proper goals or aims of human life, namely Dharma, Artha and Moksha. Hindu practices include rituals such as puja and recitations, meditation, family-oriented rites of passage, annual festivals, occasional pilgrimages; some Hindus leave their social world and material possessions engage in lifelong Sannyasa to achieve Moksha. Hinduism prescribes the eternal duties, such as honesty, refraining from injuring living beings, forbearance, self-restraint, compassion, among others; the four largest denominations of Hinduism are the Vaishnavism, Shaivism and Smartism. Hinduism is the world's third largest religion. Hinduism is the most professed faith in India and Mauritius, it is the predominant religion in Bali, Indonesia.
Significant numbers of Hindu communities are found in the Caribbean, North America, other countries. The word Hindū is derived from Indo-Aryan/Sanskrit root Sindhu; the Proto-Iranian sound change *s > h occurred between 850–600 BCE, according to Asko Parpola. It is believed that Hindu was used as the name for the Indus River in the northwestern part of the Indian subcontinent. According to Gavin Flood, "The actual term Hindu first occurs as a Persian geographical term for the people who lived beyond the river Indus", more in the 6th-century BCE inscription of Darius I; the term Hindu in these ancient records did not refer to a religion. Among the earliest known records of'Hindu' with connotations of religion may be in the 7th-century CE Chinese text Record of the Western Regions by Xuanzang, 14th-century Persian text Futuhu's-salatin by'Abd al-Malik Isami. Thapar states that the word Hindu is found as heptahindu in Avesta – equivalent to Rigvedic sapta sindhu, while hndstn is found in a Sasanian inscription from the 3rd century CE, both of which refer to parts of northwestern South Asia.
The Arabic term al-Hind referred to the people. This Arabic term was itself taken from the pre-Islamic Persian term Hindū, which refers to all Indians. By the 13th century, Hindustan emerged as a popular alternative name of India, meaning the "land of Hindus"; the term Hindu was used in some Sanskrit texts such as the Rajataranginis of Kashmir and some 16th- to 18th-century Bengali Gaudiya Vaishnava texts including Chaitanya Charitamrita and Chaitanya Bhagavata. These texts used it to distinguish Hindus from Muslims who are called Yavanas or Mlecchas, with the 16th-century Chaitanya Charitamrita text and the 17th-century Bhakta Mala text using the phrase "Hindu dharma", it was only towards the end of the 18th century that European merchants and colonists began to refer to the followers of Indian religions collectively as Hindus. The term Hinduism spelled Hindooism, was introduced into the English language in the 18th century to denote the religious and cultural traditions native to India. Hinduism includes a diversity of ideas on spirituality and traditions, but has no ecclesiastical order, no unquestionable religious authorities, no governing body, no prophet nor any binding holy book.
Because of the wide range of traditions and ideas covered by the term Hinduism, arriving at a comprehensive definition is difficult. The religion "defies our desire to define and categorize it". Hinduism has been variously defined as a religion, a religious tradition, a set of religious beliefs, "a way of life". From a Western lexical standpoint, Hinduism like other faiths is appropriately referred to as a religion. In India the term dharma is preferred, broader than the Western term religion; the study of India and its cultures and religions, the definition of "Hinduism", has been shaped by th