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=============================================================== Glossary Part 14: Terms beginning with "N" FREQUENTLY USED TERMS IN CONVENTIONAL FUSION RESEARCH AND PLASMA PHYSICS Edited by Robert F. Heeter, firstname.lastname@example.org Guide to Categories: * = plasma/fusion/energy vocabulary & = basic physics vocabulary > = device type or machine name # = name of a constant or variable ! = scientists @ = acronym % = labs & political organizations $ = unit of measurement The list of Acknowledgements is in Part 0 (intro). ================================================================== NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN # n: variable used for number density of particles. # n: also used as the symbol for a neutron. # n: also sometimes used for the index of refraction @ NAS: National Academy of Sciences; see entry @ NASA: National Aeronautics and Space Administration $ nano: metric prefix indicating 10^-9 * the base unit @ NBETF: Neutral Beam Engineering Test Facility @ NBI: Neutral Beam Injection; see entry @ NBS: National Bureau of Standards @ ND-YAG: Neodymium yttrium Aluminum Garnet # ne: (n subscript e) - usually electron density # Ne: chemical symbol for Neon. @ NERSC: National Energy Research Supercomputer Center; see entry @ NIF: National Ignition Facility; see entry @ NIKE: Naval? Inertial Confinement Experiment????; see entry @ NINJA: Neutral gas INJection Array (on Alcator C-Mod) @ NIST: National Institute for Science & Technology? @ NRC: National Research Council *OR* Nuclear Regulatory Commission; see entries. @ NRL: Naval Research Laboratory; see entry @ NSTX: National Spherical Tokamak eXperiment; see entry % National Academy of Sciences: Elite, honorary, independent, self-perpetuating organization of highly-successful scientists; chartered by the U.S. Congress to provide technical advice to the federal government upon request. % National Energy Research Supercomputer Center (NERSC): Formerly the National Magnetic Fusion Energy Computer Center, or NMFECC, NERSC is a supercomputer facility located at Livermore, CA. Originally developed to provide high-performance computing facilities for the needs of the magnetic fusion energy program, the facility now benefits all energy research programs. NERSC is a part of the Energy Sciences Network, ESNET, run by the Department of Energy, which links several of the national laboratories. > National Ignition Facility (NIF): Inertial-Confinement Fusion Facility proposed to be built at Livermore and operational around the year 2000. See Section 9 on Future Plans for more information. % National Research Council: Research arm of the National Academy of Sciences. > National Spherical Tokamak eXperiment (NSTX): Mid-sized low aspect-ratio tokamak / spheromak experiment proposal; still in design phase / not funded. See Section 9 on Future Plans for more information. % Naval Research Laboratory: Basic-science research laboratory operated by the U.S. Navy. * Neoclassical Diffusion: In a magnetized plasma, _classical_ diffusion refers to transport of particles due to Coulomb collisions, taking the spiral orbits in the magnetic field into account. In a toroidal magnetic field, the actual rate of diffusive transport is much higher due to slow changes in the positions of the centers of the spirals, known as banana orbits (see entry). This faster transport is called _neo-classical_. With very few exceptions the transport in toroidal devices is observed to be 10-100 times larger still, presumably due to small-scale turbulence. The observed transport is called _anomalous_ (although it actually is the "normal" state). * Neoclassical transport: See neo-classical diffusion. > Neutral Beam Engineering Test Facility: Facility located at LBL which tested neutral beam injection systems that were designed for use in magnetic fusion reactors. * Neutral Beam Injection: This is one of the fundamental plasma heating methods. A particle accelerator is used to create fast ion beams (the particle energies are on the order of 100 keV); the ion beam is then passed through a neutral gas region, where the ions neutralize via charge-exchange reactions with the neutral gas. The neutralized beam is then injected into a magnetically confined plasma. The neutral atoms are unaffected (not confined) by the magnetic field, but ionize as they penetrate into the plasma. The high-energy ions then transfer some of their energy to the plasma particles in repeated collisions, and heat the plasma. * Neutral Injection Concept: See Neutral Beam Injection, above. * Neutralized Plasma: Plasma with no net electrical charge. & Neutron: [Symbol: n] Fundamental atomic particle with zero electrical charge (therefore not confined by a magnetic field) and a mass roughly equal to a proton's mass. Neutrons are found in all nuclei except for ordinary hydrogen; they are also products of many nuclear reactions. Neutrons will react with nuclei, and can induce radioactivity or fission. Free neutrons which do not collide and react with a nucleus decay into an electron, a proton, and an neutrino, with a half life of about 13 minutes. * Neutron Wall Loading: Energy flux carried by fusion neutrons into the first physical boundary that surrounds the plasma (the first wall). (see also First Wall, Flux, Neutrons) > NIKE: Medium-scale(?) inertial-confinement fusion facility at the Naval Research Lab; see discussion in Section 5. * Non-Inductive Current Drive: Current drives schemes that do not rely upon the "transformer" effect in tokamaks. The attainment of non-inductive current drive is crucial to the success of tokamaks as truly steady-state devices. See also inductive current drive. > Nova: The United States' largest laser (ICF) fusion facility, and the world's most powerful laser; located at LLNL. This is a 10-beam, 100 terawatt, Nd-glass laser system, which can operate at the infrared/visible wavelengths of 1.05, 0.53, or 0.35 microns. It was completed in 1984 and is the successor to the Shiva system. (The next flagship laser-fusion facility currently planned in the U.S. is the National Ignition Facility.) * Nuclear Binding Energy: The difference between the total energy ( = mc^2) of the bound nucleus, and the energies of the individual constituent particles ( = sum of masses * c^2). The nuclear binding energy *per nucleon* is a maximum for iron. Fusion releases energy because light nuclei are less tightly bound than medium-weight nuclei, and thus energy is liberated when they become more tightly bound after fusing. Fission releases energy for the same reason - heavy nuclei are also less tightly bound than medium-weight nuclei, and energy is liberated when heavy nuclei split into lighter nuclei. & Nuclear Force: See Weak (Nuclear) Force, Strong (Nuclear) Force. % Nuclear Regulatory Commission: U.S. organization in charge of overseeing safety of nuclear facilities, including fission (and presumably fusion) reactors. * Nucleon: Generic term for a component particle of a nucleus, i.e., either a proton or a neutron. & Nucleus: The tiny core of an atom, positively charged, containing protons and neutrons (except for simple hydrogen, which has only a single proton). In an atom, electrons "orbit" the nucleus, forming a cloud around it.