 [N]- N 1. Neutron number. 2. In dosimetry, the factor designed to take into account all parameters influencing a dose equivalent , except the absorbed dose and type and energy of the radiation. .
- NAA Neutron activation analysis.
- NaI(Tl) DETECTOR A scintillation crystal made of thallium-activated sodium iodide and used as a scintillation detector.
- NATURAL ISOTOPIC ABUNDANCE See abundance, natural isotopic.
- NATURAL RADIOACTIVITY Radioactivity of naturally occurring nuclides in materials where the isotopic abundance of that nuclide is natural.
- NCA No carrier added. J.
- NDP (1). Neutron diagnostic probe. (2). Neutron depth profiling.
- NEGATRON A negative beta-particle.
- NEUTRINO Any of several neutral, possibly massless particles always involved with electrons in beta-decay nuclear transformations.
- NEUTRON ACTIVATION See activation.
- NEUTRON ACTIVATION MASS SPECTROMETRY (NAMS) A technique in which the products of activation are detected by mass spectrometry. For example, in determining boron in biological samples, neutron activation produces alphas by the 10B(n,a) reaction and the alphas are subsequently measured as 4He in the mass spectrometer. FR.
- NEUTRON CAPTURE A nuclear reaction in which a neutron is absorbed by a target nucleus producing an isotope one mass number greater in its ground or excited states.
- NEUTRON DENSITY The number of free neutrons divided by the containing volume. Partial densities may be defined for neutrons characterized by such parameters as energy and directions.
 NEUTRON DEPTH PROFILING A method of charged particle activation analysis in which deuterons of specific energy undergo (d,n) reactions in which the neutron energy spectrum is measured by time-of-flight techniques. The energy is a measure of the deuteron's energy when the reaction occurred and therefore a probe of how deep the reacting element is in the sample. The intensity of detected neutrons is a measure of reacting element concentration. NAC.- NEUTRON DIAGNOSTIC PROBE A device for prompt analysis that is a combination of a neutron generator , an alpha-particle counter for time-of-flight neutron spectrometry, and a detector for inelastic gamma-ray spectroscopy.
- NEUTRON EXCESS The number of neutrons in excess of the number of protons in a nuclide.
- NEUTRON FLUX See flux density, particle.
- NEUTRON GENERATOR 1.) An accelerator, usually small, of light charged ions (p, d, t) which produces a flux of neutrons through nuclear reactions in a light element target. 2.) Any device which produces neutrons.
- NEUTRON NUMBER The number of neutrons in a nucleus.
- NEUTRONS, COLD Neutrons with a neutron temperature considerably lower than normal room temperature.
- NEUTRONS, DELAYED Neutrons emitted by fission products formed by nuclear decay (the observed delay is due to the lifetime of the preceding nuclear decay or decays.
- NEUTRONS, EPICADMIUM Neutrons of kinetic energy greater than the effective cadmium cut-off for neutrons.
- NEUTRONS, EPITHERMAL Neutrons of kinetic energy greater than that of thermal agitation. The term is often restricted to energies just above thermal.
- NEUTRONS, FAST Neutrons of kinetic energy greater than some specified value. This value may vary over a wide range and will be dependent upon the application, such as reactor physics, shielding or dosimetry.
- NEUTRONS, FISSION Neutrons originating in the fission process which have retained their original energy.
- NEUTRONS, INTERMEDIATE Neutrons of kinetic energy between the energies of slow and fast neutrons. In reactor physics, the range might be 1 eV to 0.1 MeV.
- NEUTRONS, PROMPT Neutrons accompanying the fission process without measurable delay.
- NEUTRONS, RESONANCE Neutrons , the energy of which corresponds to the resonance energy of a specified nuclide or element. If the nuclide is not specified, the term refers to resonance neutrons of 238U.
- NEUTRONS, SLOW Neutrons of kinetic energy less than some specified value. This value may vary over a wide range and depends on the application. In reactor physics, the value is frequently chosen to be 1 eV; in dosimetry , the effective cadmium cut-off is used.
- NEUTRONS, THERMAL Neutrons in thermal equilibrium with the medium in which they exist.
- NEUTRON TEMPERATURE The temperature assigned to a population of neutrons when this population is approximated by a Maxwellian distribution. C.
- NICK TRANSLATION Labeling procedure in which DNA is first "nicked" (broken) and a radioactive nucleotide is re-included by the action of DNA polymerase. J.
- NIM MODULE An electronic component for nuclear instrumentation packaged in a standardized way to allow interchangability with alternative units and to provide compatibility with equivalently standardized housing and powering units (bins) called NIM bins.
- NIMBIN Standard bins for housing and supplying power to complementarily standardized electronics called nuclear instrument modules, or NIM modules.
- NO CARRIER ADDED A preparation of a radioactive isotope which is essentially free from stable isotopes of the element in question.
- NONACTIVATION ANALYSIS Methods of analysis based on the interaction of nuclear radiation or X-rays with the sample, leading to absorption and backscattering, not to activation of the determined component. HRC.
- NON-DESTRUCTIVE ACTIVATION ANALYSIS See activation analysis.
- NON-IONIZING RADIATION Radiation , the energy of which is insufficient to produce ions in matter. Included are microwaves, infrared light, visible light and slow neutrons. In most cases, ultraviolet radiation may be considered a non-ionizing radiation too.
- NON-SPECIFIC BINDING That portion of the tracer used in a competitive binding assay that is found in the bound fraction, independent of the binding reaction. Also expressed as minimum binding. NM.
- NRA Nuclear reaction analysis.
- NSB See non-specific binding.
- NUCLEAR ACTIVATION ANALYSIS See activation analysis.
- NUCLEAR CHEMISTRY See chemistry, nuclear.
- NUCLEAR DECAY See decay, nuclear.
- NUCLEAR EMULSION A photographic emulsion specially prepared for the detection of nuclear particles. Such emulsions are generally thicker and contain a higher concentration of silver halide than those used for standard photography. The emulsion is usually deposited on a glass plate. NM.
- NUCLEAR FISSION See fission, nuclear.
- NUCLEAR FORCE See force, nuclear.
- NUCLEAR FUSION See fusion, nuclear.
- NUCLEAR GEOLOGY Application of nuclear science and techniques to geologic studies.
- NUCLEAR ISOMERS See isomers, nuclear.
- NUCLEAR LEVEL One of the energy values at which a nucleus can exist for a measurable time (>10-22 s).
- NUCLEAR MEDICINE A branch of medicine "taken to embrace all applications of radioactive materials in diagnosis or treatment or in medical research with the exception of the use of sealed radiation sources in radiotherapy". (World Health Organization, 1972); "the clinical and laboratory medical specialty that employs for diagnosis, therapy, and research the nuclear properties of radioactive and stable nuclides to evaluate metabolic, physiologic, and pathologic conditions of the body" (American Board of Nuclear Medicine); "devoted to the diagnosis, treatment, research, and prevention of disease by making use of unsealed radioactive sources and of the properties of stable radionuclides" (Council of Europe and the Society of Nuclear Medicine Europe). Direct therapy using accelerators is also included.
- NUCLEAR MICROPROBE A charged-particle or ion beam with excellent spatial resolution and used for nuclear reaction analysis. FR.
- NUCLEAR MIGRATION Transport of nuclides from their point of origin by natural processes.
- NUCLEAR PARTICLE See particle, nuclear.
- NUCLEAR PHARMACEUTICALS See radiopharmaceuticals.
- NUCLEAR RADIUS The geometrical radius of the atomic nucleus; because of the relative incompressibility of nuclear matter, it is approximately proportional to the cube root of the atomic number of the nucleus.
- NUCLEAR REACTION A transformation of a nucleus which occurs (i ) when another nuclear particle approaches closely enough to be influenced by the mutual attractive nuclear force between them or (ii) when affected by an electromagnetic force of sufficient strength.
- NUCLEAR REACTION ANALYSIS Charged-particle induced nuclear reactions for determination of elements, usually depth profiling of light elements. FR.
- NUCLEAR REACTOR See reactor, nuclear.
- NUCLEAR RESONANCE BROADENING A technique used for obtaining concentration depth profiles by comparing resonant charged-particle capture gamma-ray yields from an unknown distribution in a sample to those yields from a known distribution of the same isotope. Frequently, the latter distribution is just the natural isotopic mixture.
- NUCLEAR RESONANCE SCATTERING Mössbauer effect.
- NUCLEAR SOLID STATE TRACK DETECTOR See solid state track detector.
- NUCLEAR SPECTROSCOPY The measurement of the energy spectrum of particles emitted or scattered from nuclei.
- NUCLEAR SPIN See spin, nuclear.
- NUCLEAR TRANSFORMATION See transformation, nuclear.
- NUCLEAR TRANSITION See transition, nuclear.
- NUCLEIDE Nuclide is preferred.
- NUCLEON A proton or a neutron.
- NUCLEONICS The practical applications of nuclear science and the techniques associated with these applications. NM.
- NUCLEON NUMBER Number of nucleons in a nucleus.
- NUCLEOPORE FILTER A filter with micron and submicron sized pores. The pores are of controlled and uniform size, produced by chemically etching radiation damage tracks of heavy ions with which the filters are bombarded as part of the production process.
- NUCLEUS The positively charged central portion of an atom , excluding the orbital electrons.
- NUCLIDE A species of an atom characterized by its mass number, atomic number and nuclear energy state, provided that the mean life in that state is long enough to be observable.
- NUCLIDIC MASS The rest mass of a nuclide expressed in atomic mass units.
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