Stockpile stewardship refers to the United States program of reliability testing and maintenance of its nuclear weapons without the use of nuclear testing. Because no new nuclear weapons have been developed by the United States since 1992 its youngest weapons are at least 26 years old. Aging weapons can fail or act unpredictably in a number of ways: the high explosives that condense their fissile material can chemically degrade, their electronic components can suffer from decay, their radioactive plutonium/uranium cores are unreliable, the isotopes used by thermonuclear weapons may be chemically unstable as well. Since the United States has not tested nuclear weapons since 1992, this leaves the task of its stockpile maintenance resting on the use of simulations and applications of scientific knowledge about physics and chemistry to the specific problems of weapons aging, it involves the manufacture of additional plutonium "pits" to replace ones of unknown quality, finding other methods to increase the lifespan of existing warheads and maintain a confident nuclear deterrent.
Most work for stockpile stewardship is undertaken at United States Department of Energy national laboratories at Los Alamos National Laboratory, Sandia National Laboratories, Lawrence Livermore National Laboratory, the Nevada Test Site, Department of Energy productions facilities, which employ around 27,500 personnel and cost billions of dollars per year to operate. The Stockpile Stewardship and Management Program is a United States Department of Energy program to ensure that the nuclear capabilities of the United States are not eroded as nuclear weapons age, it costs more than $4 billion annually to test nuclear weapons and build advanced science facilities, such as the National Ignition Facility. Such facilities have been deemed necessary under the program since President Bill Clinton signed the Comprehensive Test Ban Treaty in 1997, although building such facilities is a violation of the Non-Proliferation Treaty; the NPT requires signatory nuclear weapons states to build down their nuclear arsenals toward their complete elimination.
The US Senate never ratified the CTBT. President Obama had committed $1 trillion over 30 years to upgrade the US nuclear arsenal; the stockpile stewardship program is supported by the following experimental facilities: Dual-Axis Radiographic Hydrodynamic Test Facility, Los Alamos National Laboratory Contained Firing Facility, Lawrence Livermore National Laboratory National Ignition Facility, Lawrence Livermore National Laboratory Z machine, Sandia National Laboratories Omega, Laboratory for Laser Energetics High Explosive Application Facility, Lawrence Livermore National Laboratory Joint Actinide Shock Physics Experimental Research, Nevada National Security Site Large Bore Powder Gun, Nevada National Security Site Los Alamos Neutron Science Center, Los Alamos National Laboratory Proton Radiography, Los Alamos National Laboratory Big Explosives Experimental Facility, Nevada National Security Site TA-55, Los Alamos National Laboratory U1a Facility, Nevada National Security SiteThe data produced by the experiments carried out in these facilities is used in combination with the Advanced Simulation and Computing Program.
Enduring Stockpile "2007 DOE Stockpile Stewardship Report". Federation of American Scientists. Collina, Tom Zamora. "The Impact of Emerging Technologies: The National Ignition Facility: Buyer Beware". Technology Review. Archived from the original on 2006-01-16. Retrieved 2009-10-24; the Stockpile Stewardship and Management Program "Remanufacturing of nuclear-weapon components within the DOE's Stockpile Stewardship Program". Federation of American Scientists
The neutron is a subatomic particle, symbol n or n0, with no net electric charge and a mass larger than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave within the nucleus, each has a mass of one atomic mass unit, they are both referred to as nucleons, their properties and interactions are described by nuclear physics. The chemical and nuclear properties of the nucleus are determined by the number of protons, called the atomic number, the number of neutrons, called the neutron number; the atomic mass number is the total number of nucleons. For example, carbon has atomic number 6, its abundant carbon-12 isotope has 6 neutrons, whereas its rare carbon-13 isotope has 7 neutrons; some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes. Within the nucleus and neutrons are bound together through the nuclear force. Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen atom.
Neutrons are produced copiously in nuclear fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission and neutron capture processes; the neutron is essential to the production of nuclear power. In the decade after the neutron was discovered by James Chadwick in 1932, neutrons were used to induce many different types of nuclear transmutations. With the discovery of nuclear fission in 1938, it was realized that, if a fission event produced neutrons, each of these neutrons might cause further fission events, etc. in a cascade known as a nuclear chain reaction. These events and findings led to the first self-sustaining nuclear reactor and the first nuclear weapon. Free neutrons, while not directly ionizing atoms, cause ionizing radiation; as such they can be a biological hazard, depending upon dose. A small natural "neutron background" flux of free neutrons exists on Earth, caused by cosmic ray showers, by the natural radioactivity of spontaneously fissionable elements in the Earth's crust.
Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation and in neutron scattering experiments. An atomic nucleus is formed by a number of protons, Z, a number of neutrons, N, bound together by the nuclear force; the atomic number defines the chemical properties of the atom, the neutron number determines the isotope or nuclide. The terms isotope and nuclide are used synonymously, but they refer to chemical and nuclear properties, respectively. Speaking, isotopes are two or more nuclides with the same number of protons; the atomic mass number, symbol A, equals Z+N. Nuclides with the same atomic mass number are called isobars; the nucleus of the most common isotope of the hydrogen atom is a lone proton. The nuclei of the heavy hydrogen isotopes deuterium and tritium contain one proton bound to one and two neutrons, respectively. All other types of atomic nuclei are composed of two or more protons and various numbers of neutrons.
The most common nuclide of the common chemical element lead, 208Pb, has 82 protons and 126 neutrons, for example. The table of nuclides comprises all the known nuclides. Though it is not a chemical element, the neutron is included in this table; the free neutron has 1.674927471 × 10 − 27 kg, or 1.00866491588 u. The neutron has a mean square radius of about 0.8×10−15 m, or 0.8 fm, it is a spin-½ fermion. The neutron has no measurable electric charge. With its positive electric charge, the proton is directly influenced by electric fields, whereas the neutron is unaffected by electric fields; the neutron has a magnetic moment, however. The neutron's magnetic moment has a negative value, because its orientation is opposite to the neutron's spin. A free neutron is unstable, decaying to a proton and antineutrino with a mean lifetime of just under 15 minutes; this radioactive decay, known as beta decay, is possible because the mass of the neutron is greater than the proton. The free proton is stable. Neutrons or protons bound in a nucleus can be stable or unstable, depending on the nuclide.
Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force, it requires the emission or absorption of electrons and neutrinos, or their antiparticles. Protons and neutrons behave identically under the influence of the nuclear force within the nucleus; the concept of isospin, in which the proton and neutron are viewed as two quantum states of the same particle, is used to model the interactions of nucleons by the nuclear or weak forces. Because of the strength of the nuclear force at short distances, the binding energy of nucleons is more than seven orders of magnitude larger than the electromagnetic energy binding electrons in atoms. Nuclear reactions therefore have an energy density, more than ten million times that of chemical reactions; because of the mass–energy equivalence, nuclear binding energies reduce the mass of nuclei. The ability of the nuclear force to store energy arising from the electromagnetic repulsion of nuclear components is the basis for most of the energy that makes nuclear reactors or bombs possible.
In nuclear fission, the absorption of a neutron by a heavy nuclide causes the nuclide to become unstable and break into light nuclides and additional neu
The W-71 nuclear warhead was a US thermonuclear warhead developed at Lawrence Livermore National Laboratory in California and deployed on the LIM-49A Spartan missile, a component of the Safeguard Program, an anti-ballistic missile defense system deployed by the US in the 1970s. The W-71 warhead was designed to intercept incoming enemy warheads at long range, as far as 450 miles from the launch point; the interception took place at such high altitudes, comparable to low earth orbit, where there is no air. At these altitudes, x-rays resulting from the nuclear explosion can destroy incoming reentry vehicles at distances on the order of 10 miles, which made the problem of guiding the missile to the required accuracies much simpler than earlier designs that had lethal ranges of less than 1,000 feet; the W-71 warhead had a yield of around 5 megatons of TNT. The warhead package was a cylinder, 42 inches in diameter and 101 inches long; the complete warhead weighed around 2,850 pounds. The W71 produced great amounts of x-rays, needed to minimize fission output and debris to reduce the radar blackout effect that fission products and debris produce on anti-ballistic missile radar systems.
The W71 design emerged in the mid-1960s as the result of studies of earlier high-altitude nuclear tests carried out before the Partial Nuclear Test Ban Treaty of 1963. A number of tests those of Operation Fishbowl in 1962, demonstrated a number of poorly understood or underestimated effects. Among these was the behaviour of x-rays created during the explosion; these tended to react with the atmosphere within a few tens of meters at low altitudes. At high altitudes, lacking an atmosphere to interact with, the mean free path of the x-rays could be on the order of tens of kilometers; this presented a new method of attacking enemy nuclear reentry vehicles while still at long range from their targets. X-rays hitting the warhead's outermost layer will react by heating a thin layer of the material so that shock waves develop that can cause the heat shield material on the outside of the RV to separate or flake off; the RV would break up during reentry. The major advantage of this attack is that it takes place over long distances, as great as 30 kilometres, which covers the majority of the threat tube containing the warhead and the various radar decoys and clutter material that accompanies it.
The ABM had to approach within less than 800 feet of the warhead to damage it through neutron heating, which presented a serious problem attempting to locate the warhead within a threat tube, at least a kilometer across and about ten long. Bell received a contract to begin conversion of the earlier LIM-49 Nike Zeus missile for the extended range role in March 1965; the result was the Zeus EX, or DM-15X2, which used the original Zeus' first stage as the second stage along with a new first stage to offer much greater range. The design was renamed keeping the original LIM-49 designation. Tests of the new missile stated in April 1970 from Meck Island, part of the Kwajalein Test Range, set up to test the earlier Nike Zeus system; because of a perceived need to deploy the system, the team took a "do it once, do it right" approach in which the original test items were designed to be the production models. The warhead for Spartan was designed by Lawrence Livermore National Laboratory, drawing on previous experience from Operation Plowshare.
A nuclear explosion at high altitude has the disadvantage of creating a significant amount of electronic noise and an effect known as nuclear blackout that blinds radars over a large area. Some of these effects are due to the fission fragments being released by the explosion, so care was taken to design the bomb to be "clean" to reduce these effects. Project Plowshares had explored the design of such clean bombs as part of an effort to use nuclear explosives for civilian uses where the production of long-lived radionuclides had to be minimized. To maximize the production of x-rays, the W-71 is reported to have used a gold tamper, rather than the usual depleted uranium or lead; the lining serves the primary purpose of capturing x-ray energy within the bomb casing while the primary is exploding and triggering the secondary. For this purpose, most any high-z metal will work, depleted uranium is used because the neutrons released by the secondary will cause fission in this material and add a significant amount of energy to the total explosive release.
In this case the increase in blast energy would have no effect as there is little or no atmosphere to carry that energy, so this reaction is of little value. The use of gold maximizes the production of x-rays as gold efficiently radiates thermal x-rays; this efficient release of x-rays when heated is the same reason that inertial confinement fusion experiments like the National Ignition Facility use gold-covered targets. In Congressional testimony on potential dismantling of the W71, a DOE official described the warhead as "a gold mine". Another advantage of using a gold tamper and lining is that neutron capture events form Au-198 which has a half life of 2.697 days and beta decay energy of 0.41 MeV, in the hard x-ray to gamma ray spectrum. This helps reduce the nuclear blackout effects. Under good conditions, the W-71 warhead had a lethal exo-atmospheric radius as much as 30 miles, although it was stated to be 12 miles against "soft" targets, as little as 4 miles against hardened warheads. There were 30 to 39 units were produced between 1974 and 1975.
The weapons went into service, but were taken r
Ernest Orlando Lawrence was a pioneering American nuclear scientist and winner of the Nobel Prize in Physics in 1939 for his invention of the cyclotron. He is known for his work on uranium-isotope separation for the Manhattan Project, as well as for founding the Lawrence Berkeley National Laboratory and the Lawrence Livermore National Laboratory. A graduate of the University of South Dakota and University of Minnesota, Lawrence obtained a PhD in physics at Yale in 1925. In 1928, he was hired as an associate professor of physics at the University of California, becoming the youngest full professor there two years later. In its library one evening, Lawrence was intrigued by a diagram of an accelerator that produced high-energy particles, he contemplated how it could be made compact, came up with an idea for a circular accelerating chamber between the poles of an electromagnet. The result was the first cyclotron. Lawrence went on to build a series of larger and more expensive cyclotrons, his Radiation Laboratory became an official department of the University of California in 1936, with Lawrence as its director.
In addition to the use of the cyclotron for physics, Lawrence supported its use in research into medical uses of radioisotopes. During World War II, Lawrence developed electromagnetic isotope separation at the Radiation Laboratory, it used devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. A huge electromagnetic separation plant was built at Oak Ridge, which came to be called Y-12; the process was inefficient. After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs, was a forceful advocate of "Big Science", with its requirements for big machines and big money. Lawrence backed Edward Teller's campaign for a second nuclear weapons laboratory, which Lawrence located in Livermore, California. After his death, the Regents of the University of California renamed the Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory after him. Chemical element number 103 was named lawrencium in his honor after its discovery at Berkeley in 1961.
Ernest Orlando Lawrence was born in Canton, South Dakota on August 8, 1901. His parents, Carl Gustavus and Gunda Lawrence, were both the offspring of Norwegian immigrants who had met while teaching at the high school in Canton, where his father was the superintendent of schools, he had a younger brother, John H. Lawrence, who would become a physician, was a pioneer in the field of nuclear medicine. Growing up, his best friend was Merle Tuve, who would go on to become a accomplished physicist. Lawrence attended the public schools of Canton and Pierre enrolled at St. Olaf College in Northfield, but transferred after a year to the University of South Dakota in Vermillion, he completed his bachelor's degree in chemistry in 1922, his Master of Arts degree in physics from the University of Minnesota in 1923 under the supervision of William Francis Gray Swann. For his master's thesis, Lawrence built an experimental apparatus that rotated an ellipsoid through a magnetic field. Lawrence followed Swann to the University of Chicago, to Yale University in New Haven, where Lawrence completed his Doctor of Philosophy degree in physics in 1925 as a Sloane Fellow, writing his doctoral thesis on the photoelectric effect in potassium vapor.
He was elected a member of Sigma Xi, and, on Swann's recommendation, received a National Research Council fellowship. Instead of using it to travel to Europe, as was customary at the time, he remained at Yale University with Swann as a researcher. With Jesse Beams from the University of Virginia, Lawrence continued to research the photoelectric effect, they showed that photoelectrons appeared within 2 x 10−9 seconds of the photons striking the photoelectric surface—close to the limit of measurement at the time. Reducing the emission time by switching the light source on and off made the spectrum of energy emitted broader, in conformance with Werner Heisenberg's uncertainty principle. In 1926 and 1927, Lawrence received offers of assistant professorships from the University of Washington in Seattle and the University of California at a salary of $3,500 per annum. Yale promptly matched the offer of the assistant professorship, but at a salary of $3,000. Lawrence chose to stay at the more prestigious Yale, but because he had never been an instructor, the appointment was resented by some of his fellow faculty, in the eyes of many it still did not compensate for his South Dakota immigrant background.
Lawrence was hired as an associate professor of physics at the University of California in 1928, two years became a full professor, becoming the university's youngest professor. Robert Gordon Sproul, who became university president the day after Lawrence became a professor, was a member of the Bohemian Club, he sponsored Lawrence's membership in 1932. Through this club, Lawrence met William Henry Crocker, Edwin Pauley, John Francis Neylan, they were influential men who helped him obtain money for his energetic nuclear particle investigations. There was great hope for medical uses to come from the development of particle physics, this led to much of the early funding for advances Lawrence was able to obtain. While at Yale, Lawrence met Mary Kimberly Blumer, the eldest of four daughters of George Blumer, the dean of the Yale School of Medicine, they first met in 1926 and became engaged in 1931, were married on May 14, 1932, at Trinity Church on the Green in New Haven, Connecticut. They had six children: Eric, Mary, Robert and Susan.
Lawrence named his son Robert after theoretical phys
An electric field surrounds an electric charge, exerts force on other charges in the field, attracting or repelling them. Electric field is sometimes abbreviated as E-field. Mathematically the electric field is a vector field that associates to each point in space the force per unit of charge exerted on an infinitesimal positive test charge at rest at that point; the SI unit for electric field strength is volt per meter. Newtons per coulomb is used as a unit of electric field strengh. Electric fields are created by time-varying magnetic fields. Electric fields are important in many areas of physics, are exploited electrical technology. On an atomic scale, the electric field is responsible for the attractive force between the atomic nucleus and electrons that holds atoms together, the forces between atoms that cause chemical bonding. Electric fields and magnetic fields are both manifestations of the electromagnetic force, one of the four fundamental forces of nature. From Coulomb's law a particle with electric charge q 1 at position x 1 exerts a force on a particle with charge q 0 at position x 0 of F = 1 4 π ε 0 q 1 q 0 2 r ^ 1, 0 where r 1, 0 is the unit vector in the direction from point x 1 to point x 0, ε0 is the electric constant in C2 m−2 N−1When the charges q 0 and q 1 have the same sign this force is positive, directed away from the other charge, indicating the particles repel each other.
When the charges have unlike signs the force is negative, indicating the particles attract. To make it easy to calculate the Coulomb force on any charge at position x 0 this expression can be divided by q 0, leaving an expression that only depends on the other charge E = F q 0 = 1 4 π ε 0 q 1 2 r ^ 1, 0 This is the electric field at point x 0 due to the point charge q 1. Since this formula gives the electric field magnitude and direction at any point x 0 in space it defines a vector field. From the above formula it can be seen that the electric field due to a point charge is everywhere directed away from the charge if it is positive, toward the charge if it is negative, its magnitude decreases with the inverse square of the distance from the charge. If there are multiple charges, the resultant Coulomb force on a charge can be found by summing the vectors of the forces due to each charge; this shows the electric field obeys the superposition principle: the total electric field at a point due to a collection of charges is just equal to the vector sum of the electric fields at that point due to the individual charges.
E = E 1 + E 2 + E 3 + ⋯ = 1 4 π ε 0 q 1 2 r ^ 1 + 1 4 π ε 0 q 2 ( x 2 −
Novette was a two beam neodymium glass testbed laser built at Lawrence Livermore National Laboratory in about 15 months throughout 1981 and 1982 and was completed in January 1983. Novette was made using recycled parts from the dismantled Shiva and Argus lasers and borrowed parts from the future Nova laser, its main intended purpose was to validate the proposed design and expected performance of the planned Nova laser. In addition to being used for the further study of enhanced laser to target plasma energy coupling utilizing frequency tripled light and examining its benefits with respect to inertial confinement fusion, Novette was used in the world's first laboratory demonstration of an x-ray laser in 1984. List of laser articles List of laser types http://www.osti.gov/bridge/servlets/purl/16710-UOC0xx/native/16710.pdf http://adsabs.harvard.edu/abs/1985EnTR........15
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light propagates through the material. It is defined as n = c v, where c is the speed of light in vacuum and v is the phase velocity of light in the medium. For example, the refractive index of water is 1.333, meaning that light travels 1.333 times as fast in vacuum as in water. The refractive index determines how much the path of light is bent, or refracted, when entering a material; this is described by Snell's law of refraction, n1 sinθ1 = n2 sinθ2, where θ1 and θ2 are the angles of incidence and refraction of a ray crossing the interface between two media with refractive indices n1 and n2. The refractive indices determine the amount of light, reflected when reaching the interface, as well as the critical angle for total internal reflection and Brewster's angle; the refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/n, the wavelength in that medium is λ = λ0/n, where λ0 is the wavelength of that light in vacuum.
This implies that vacuum has a refractive index of 1, that the frequency of the wave is not affected by the refractive index. As a result, the energy of the photon, therefore the perceived color of the refracted light to a human eye which depends on photon energy, is not affected by the refraction or the refractive index of the medium. While the refractive index affects wavelength, it depends on photon frequency and energy so the resulting difference in the bending angle causes white light to split into its constituent colors; this is called dispersion. It can be observed in prisms and rainbows, chromatic aberration in lenses. Light propagation in absorbing materials can be described using a complex-valued refractive index; the imaginary part handles the attenuation, while the real part accounts for refraction. The concept of refractive index applies within the full electromagnetic spectrum, from X-rays to radio waves, it can be applied to wave phenomena such as sound. In this case the speed of sound is used instead of that of light, a reference medium other than vacuum must be chosen.
The refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299792458 m/s, the phase velocity v of light in the medium, n = c v. The phase velocity is the speed at which the crests or the phase of the wave moves, which may be different from the group velocity, the speed at which the pulse of light or the envelope of the wave moves; the definition above is sometimes referred to as the absolute refractive index or the absolute index of refraction to distinguish it from definitions where the speed of light in other reference media than vacuum is used. Air at a standardized pressure and temperature has been common as a reference medium. Thomas Young was the person who first used, invented, the name "index of refraction", in 1807. At the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers; the ratio had the disadvantage of different appearances. Newton, who called it the "proportion of the sines of incidence and refraction", wrote it as a ratio of two numbers, like "529 to 396".
Hauksbee, who called it the "ratio of refraction", wrote it as a ratio with a fixed numerator, like "10000 to 7451.9". Hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in 1807. In the next years, others started using different symbols: n, m, µ; the symbol n prevailed. For visible light most transparent media have refractive indices between 1 and 2. A few examples are given in the adjacent table; these values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, as is conventionally done. Gases at atmospheric pressure have refractive indices close to 1 because of their low density. All solids and liquids have refractive indices above 1.3, with aerogel as the clear exception. Aerogel is a low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the other end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, but some high-refractive-index polymers can have values as high as 1.76.
For infrared light refractive indices can be higher. Germanium is transparent in the wavelength region from 2 to 14 µm and has a refractive index of about 4. A type of new materials, called topological insulator, was found holding higher refractive index of up to 6 in near to mid infrared frequency range. Moreover, topological insulator material are transparent; these excellent properties make them a type of significant materials for infrared optics. According to the theory of relativity, no information can travel faster than the speed of light in vacuum, but this does not mean that the refractive index cannot be lower than 1; the refractive index measures the phase velocity of light. The phase velocity is the speed at which the crests of the wave move and can be faster than the speed of light in vacuum, thereby give a refractive index below 1; this can occur close to resonance frequencies, for absorbing media, in plasmas, for X-rays. In the X-ray regime the refractive indices are