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Explosives Glossary

Free Stuff May 21, 2008


Alarm: a signal given by an EDS that indicates to the operator that a detection of explosive material has been made. For a technological system such as an IMS the alarm might be either audio (e.g., a buzzer sounds) or visual (e.g., a message on a computer screen). In the case of a canine, the alarm is some form of behaviour by the dog which the handler interprets as a detection.

Alarm resolution: the process by which an operator determines whether an alarm is the result of a threat item being present, or whether in fact there is no threat item present.

Alarm threshold setting: the signal level above which an EDS is set to alarm. An EDS may make a detection of an amount of explosive below the alarm threshold setting, but it will then be assumed that the signal obtained is either (1) a nuisance alarm or (2) noise.

Ammonia dynamites: a class of dynamites in which a portion of the nitroglycerin is replaced by ammonium nitrate and nitroglycol. These dynamites are lower in cost and less sensitive to shock and friction than straight dynamites.

Ammonia-gelatin dynamites: gelatin dynamites where part of the nitroglycerin/nitrocellulose gel is replaced by less costly ammonium nitrate.

Ammonium nitrate: an explosive compound, NH4NO3. It is the main ingredient of ANFO, and of some water-gel explosives.

Analyte: in analytical chemistry, the compound that is being studied, analysed, or identified.

ANFO: a mixture of ammonium nitrate and fuel oil, often used in vehicle bombs.

Astrolite: a commercially available two-part explosive. One component is a liquid and the other is a solid.

Attenuation coefficient: a measure of how much an incident probe (e.g., electromagnetic radiation) is attenuated as it passes through a given substance.

Atomic explosion: an explosion caused by the breaking up (fission) or joining together (fusion) of atomic nuclei. This is the type of explosion occurring when a nuclear weapon is detonated.

Atomic number: the total number of protons in the nucleus of an atom, equal to the nuclear charge. Represented by the symbol Z.

Backscatter x-ray system: any x-ray system that detects objects (including explosives) based on the images produced from reflected x-rays.

Binary explosive: an explosive material containing two different explosive compounds.

Black powder: a low explosive which is a mixture of potassium nitrate (KNO3), charcoal, and sulfur. It is frequently used in mail bombs and pipe bombs.

Blasting agent: a chemical composition or mixture, consisting mainly of ammonium nitrate, which will detonate when initiated by high explosive primers or boosters. Blasting agents contain no nitroglycerin and are relatively insensitive to shock and friction.

Blasting cap: a device containing a small amount of primary high explosive, used for detonating a main charge of secondary high explosive.

Blasting slurries: a blasting agent consisting of NCN mixtures in a gel-like consistency.

Blast pressure wave: the wave of hot, very high-pressure gases travelling outward from an explosive detonation. The effect of this wave decreases as distance from the point of explosion increases.

Bomb: any device containing explosive or incendiary material that is designed to explode or ignite upon receiving the proper external stimulus.

Bombing: an illegal detonation or ignition of an explosive or incendiary device.

Bomb detection: the discovery and identification of bombs that are being smuggled, or used for some illicit purpose. Bomb detection differs from explosives detection in that the detection may or may not be based on the detection of the explosive material in the bomb. The detection may be based on the detection of some other bomb component, such as metal parts that are identified using metal detection.

Bonding agent: a material that is added to a chemical mixture in order to help bind the
components together.

Boosters: secondary explosives placed between the primary high explosive (blasting cap) and the main explosive charge, with the purpose of amplifying the detonation wave from the primary high explosive.

Brisance: the destructive fragmentation effect of a charge on its immediate vicinity.

Bulk explosives detection system: any EDS which directly detects a macroscopic solid mass of explosive material. This is often (but not always) accomplished using x-ray technology, with the explosive material being observed as an object on the x-ray image. Bulk detection is in contrast to trace detection, where the explosive material is detected from vapour or particulate residue. In contrast to a trace detection system, a bulk detection system will never detect explosives if only residue is present.

C-3: a military plastic explosive, composed of approximately 80 percent RDX and 20 percent plasticizer. Also known as composition C-3, it was the predecessor to C-4.

C-4: a military plastic explosive composed primarily (approximately 90 percent) of RDX. Also known as composition C-4.

Canine detection: the detection of explosives, narcotics, or other types of chemical compounds through the use of a dog that is trained to sniff out these substances.

Carrier gas: In IMS technology, the carrier gas (also called dopant) is a gas which is added to the inlet air flow containing the sample. The purpose of the carrier gas is to enhance the ionization process, and in some cases to make the sample molecules easier to detect via the formation of a chemical adduct (i.e., a species consisting of the sample molecule attached to a carrier gas molecule or fragment).

Cavity charge: a shaped charge.

Certification: a process through which an EDS is tested and, if it performs successfully, is judged to be suitable for certain applications.

Cf: Californium, a radioactive element that emits neutrons and can be used as a neutron source.

Chemical explosion: an explosion caused by the extremely rapid conversion of a solid or liquid explosive into gases having a much greater volume than the original material.

Chemiluminescence: a trace detection technique in which explosives are detected via light that is emitted from NO molecules in a chemically excited state. The excited state NO molecules are formed through deliberately induced decomposition of the nitro (NO2) groups in the original explosive compound.

Combustible: a material capable of igniting or burning.

Commercial explosives detection system: any EDS that can be purchased on the open market.

Composition B: a plastic explosive that contains approximately equal amounts of TNT and RDX.

Computer tomography, computed tomography: an x-ray technique in which transmission images (“slices”) taken at many different angles through an object are put together to produce a three-dimensional image of the object.

Contraband: any item or material that is smuggled into an area or facility where it is prohibited. For example, in a prison contraband might include weapons, explosives, and narcotics.

Conical-shaped charge: a cone-shaped explosive charge, employed to cut or punch a hole through a target.

Cordeau Detonant: a brand name for detonating cord.

CT: computer tomography.

Deflagration: a subsonic process by which explosives release their energy through a rapid burning or autocombustion process, this process being sustained by the energy release from the material. Low explosives explode via deflagration, and under some circumstances high explosives do also. The terms explosion and deflagration are sometimes used synonymously, with both being in contrast to detonation.

Density: the mass of a substance per unit volume, usually expressed in units of grams per cubic centimetre (gr/cm3).

Detacord: a brand name for detonating cord.

Datasheet: a plastic explosive with a sheet-like structure, containing PETN as the explosive ingredient.

Detonating cord: a cord-like synthetic explosive product, containing PETN as the explosive ingredient.

Detonating Fuse: a brand name for detonating cord.

Detonation: the supersonic process by which a high explosive decomposes and liberates its energy from shock wave compression.

Detonation velocity: the speed at which the shock wave travels through an explosive material.

Detonator: a device, such as a fuse or blasting cap, used to set off explosives.

Dielectric constant: the ratio of electric flux density produced by an electric field in a given material, compared to the density produced by the same field in vacuum. Also called permittivity.

Ditching dynamite: a form of straight dynamite widely used in commercial blasting operations. It is characterized by a high detonation velocity of over 5,185 m/s (17,000 ft/s).

DNT: 2,4-dinitrotoluene, a high explosive compound with a rather high vapour pressure (near one part per million). Molecular formula C7H6N2O4; molecular weight = 182.

Dopant: carrier gas.

Double-beam backscatter x-ray system: a backscatter x-ray system in which there are two x-ray sources and two detectors, so that both sides of an investigated article can be looked at simultaneously.

Dual-axis x-ray system: an x-ray system in which the object under investigation is examined with two x-ray beams coming in at two different angles.

Dual-energy x-ray system: an x-ray system in which the object under investigation is simultaneously irradiated with x-ray beams of two different energies. This allows a wider range of target materials to be detected than if only one beam of one energy were used.

Dynamite: a solid synthetic explosive material, widely used in blasting operations. Dynamite usually contains nitroglycerin as a major explosive component.

ECD: electron capture detector.

Eddy current: a current that is induced around a closed conducting loop by the application of an external magnetic field. Eddy currents currently form the basis of most portal metal detectors.

EDS: explosives detection system.

Effective atomic number: for a substance made up of more than one element, the apparent atomic number that results if the substance is treated as if it were composed only of a single element. It is closely related to the weighted average of the atomic numbers of the constituent elements.

EGDN: ethylene glycol dinitrate. This is a high vapour pressure high explosive that is one of the main explosive ingredients in certain types of dynamite. Its molecular formula is C2H4N2O6; molecular weight = 152.

Electric blasting cap: a blasting cap that is initiated by passing electric current through a bridge wire, thus igniting the primary explosive present in the cap.

Electroluminescent image panel: a panel that is capable of converting electric energy into light.

Electron capture detector: a type of explosives detector wherein gas phase explosives molecules capture electrons from an electron-emitting source to form negative ions. The presence of an explosive is then deduced by observing a decrease in the electron current delivered from the emitting source to a detector.

Electronegativity: the tendency of a molecule to attach an electron.

Explosive bombing: the illegal explosion of a device containing high or low explosive material.

Explosive mixture: a low explosive material composed of a mixture of a combustible and an

Explosives: Explosives are compounds or mixtures of compounds which when subjected to the appropriate stimulus (heat, shock, friction, etc.) undergo extremely rapid chemical changes that result in the evolution of large volumes of highly heated gases and exert pressure upon the surrounding medium. Explosives can be thought of as energy packets that can release their energy in the microsecond time frame.

Explosives detection system: any device, person, or animal which serves the purpose of detecting explosives. Examples include an ion mobility spectrometer, an x-ray scanner for screening luggage, a trained canine with a handler, and a security guard conducting manual inspection of backpacks and briefcases.

Explosive train: a series of explosions specifically arranged to produce a desired outcome.

EXPRAY: a commercially available, aerosol-based field test kit, able to detect most explosives. Detection is based on colour changes of a special paper when it is treated with one of three types of aerosol spray.

False alarm: any alarm of an EDS which occurs when no explosive material or explosive residue is really present. Such alarms may be caused by chemically similar innocuous compounds, or by system malfunction.

False negative: an indication from an EDS that a person or item being screened for explosives is free of explosive material, when in fact the person or item does have/contain explosives.

False positive: an indication from an EDS that a person or item being screened for explosives has/contains explosive material, when in fact the person or item does not have/contain explosive material.

Flex-X: a military name for Detasheet.

Fluorophore: material capable of fluorescence.

Fluoroscopic imaging: use of a fluorescent screen to view the contents of an opaque object, with the contents appearing as shadows formed by transmission of x-rays through the object.

Forensics: In the sense used herein, the science of trace explosives analysis as related to criminal investigations or other law enforcement work.

Fragmentation bomb: a bomb such as a pipe bomb where explosive material is placed inside a metal or other solid casing, with the casing breaking into fragments that are hurled about the area at high velocity when the bomb explodes.

Free-running explosives: group of blasting agents consisting of NCN in small pellet or granular form.

Ft/s: feet per second, the standard unit for detonation velocities.

Gamma rays: high-energy electromagnetic radiation emitted by certain atoms when they are properly stimulated, as in the technique of TNA.

Gelatin dynamites: a class of dynamites with an explosive base of water-resistant gel, formed by combining nitrocellulose and nitroglycerin.

Granulation: the grain size of an explosive powder, such as black powder.

Guncotton: nitrocellulose.

Handler: the individual controlling a dog that is trained to sniff out explosives or narcotics.

HE: high explosive.

High explosives: explosives that are capable of detonation. Common examples include TNT, RDX, PETN, NG, and EGDN.

High-explosive train: an explosive train involving high explosives.

High-order detonation: complete detonation of an explosive at its highest possible detonation velocity.

HMX: a high explosive, chemically related to RDX. HMX (Her Majesty’s Explosive) is an eight membered ring of alternating carbon and nitrogen atoms, with nitro (NO2) groups attached to the nitrogens. Molecular formula C4H8N8O8, molecular weight = 296. HMX has an extremely low vapour pressure and hence is very difficult to detect using any vapour sniffing technique.

Hydrazine: liquid component of the two-part explosive Astrolite. Hydrazine is also used in rocket fuel.

Hygroscopic: readily absorbing moisture, as from the atmosphere.

Immunochemical: relating to antibody-based techniques applied to trace chemical detection.

Improvised device: a homemade device filled with explosive or incendiary material and containing the components necessary to initiate the device.

Incendiary device: a device constructed with flammable materials designed to produce a burning effect.

Incendiary thermal effect: the burning effect of an explosion. It is relatively insignificant compared to the blast pressure effect.

Infrared radiation: electromagnetic radiation that is less energetic than visible light and more energetic than microwaves.

Instantaneous combustion: a colloquial term for detonation. Detonation is in reality not truly instantaneous, but occurs in a matter of microseconds.

Interference, interferent: any chemical compound that serves to mask the presence of an explosive from a given explosives detection system.

Ion mobility spectrometer (IMS): a trace chemical detector which detects explosives and other chemical compounds using the technique of ion mobility spectrometry.

Ion mobility spectrometry: a technique for the trace detection of explosives and other chemical compounds. In this technique, compounds are first ionized, then identified based on the time that it takes them to travel through a region with an applied electric field.

Jet: the extremely hot, swiftly moving bundle of gases and concentrated power resulting from a directionally directed explosion.

Jet-Axe: a commercially available linear-shaped charge, used to cut through doors, roofs, and walls to obtain access into a building.

Kine-Pak: a commercially available two-part explosive, having excellent shock resistance even after mixture of the two components.

KV: kilovolts, a unit of energy.

KVp: kilovolts potential, x-ray source voltage descriptor.

Lead azide: a primary high-explosive compound, Pb(N3)2.

Lead styphnate: a primary high explosive, often used in blasting caps, C6H3N3O9Pb.

Linear-shaped charge: a type of shaped charge used to cut or slice a target.

Low explosives: explosives which do not detonate, but rather explode via the process of deflagration.

Low-explosive train: an explosive train employing only low explosives.

Low-order detonation: incomplete detonation of an explosive, or detonation at less than maximum detonation velocity.

Magnetic moment: a property of the nucleus of atoms that have a non-zero nuclear spin. These atoms are affected by the application of an external magnetic field, and can give rise to an NMR spectrum.

Mail bomb: any bomb that is sent through the postal service in a letter or package. It is usually designed to detonate when the letter or package is opened.

Mass spectrometer: an instrument that performs mass spectrometry.

Mass spectrometry: a chemical analysis technique in which the molecules to be studied are first ionized and then separated and identified based on their charge-to-mass ratio. Mass spectrometry is performed under conditions of high vacuum, in contrast to IMS which is performed at atmospheric pressure.

Mechanical explosion: an explosion caused by the buildup of excessive pressure inside a solid container, the pressure buildup resulting from the application of heat and hence vaporization of a material inside the container.

Mercury fulminate: a primary high-explosive compound, Hg(OCN)2.

Metal detection: the detection of metals and other conducting materials, usually based on the detection of eddy currents in an applied magnetic field.

Microgram: one millionth of one gram, usually written as mg.

Microrem: a unit of radiation dosage, equal to one millionth of a rem.

Microsecond: one millionth of 1 second, usually written as ms.

Microwaves: electromagnetic radiation that is less energetic than infrared radiation but more energetic than radio waves.

Military dynamite: an explosive (not a true dynamite) used in military construction and demolition work. It is composed of 75 percent RDX, 15 percent TNT, 5 percent motor oil, and 5 percent cornstarch.

Military explosives: explosives manufactured primarily for military applications. Examples include TNT, tetrytol, and C-4.

Milking: a dangerous process by which nitroglycerin is extracted from dynamite.

Milligram: one-thousandth of one gram, usually written as mg.

Millimetre waves: electromagnetic radiation (microwaves) having a wavelength on the order of a few millimetres.

Mine detection: the detection of land or sea mines that are buried or submerged. The detection may be made using metal detection, explosives detection, or some other detection technique.

Nanogram: one-billionth of one gram, usually written as ng.

NCN: nitro-carbo-nitrates.

Negative-pressure phase: the time period following an explosion and after the passing of the outward-going blast pressure wave, during which the pressure at a given point is below atmospheric pressure and air is sucked back into the area. Also called the suction phase. It is less powerful than the positive-pressure phase, but of longer duration.

Nerve agents: chemical agents that harm humans by attacking the nervous system.

Neutron: an elementary particle; along with protons and electrons, one of the three particles that make up atoms. Used as a probe to look for explosives in the technique of thermal neutron activation. Neutrons are neutral (i.e., they have no electrostatic charge).

NG: nitroglycerin.

Nitro-carbo-nitrates: a type of blasting agent, composed primarily of ammonium nitrate and oil.

Nitrocellulose: a cotton-like polymer treated with sulfuric and nitric acids, and used in the
manufacture of certain explosives.

Nitroglycerin, nitroglycerine: a high vapour pressure (vapour pressure approximately one part per million) high-explosive compound that is the explosive ingredient in certain types of dynamite. Molecular formula C3H5N3O9; molecular weight = 227.

NMR: nuclear magnetic resonance.

Non-electric blasting cap: a blasting cap in which the primary explosive material is set off using a flame.

Nuclear detection system: any bulk explosives detection system based on the properties of the nuclei of the individual atoms within the explosives material, including TNA, NMR, and QR systems.

Nuclear magnetic resonance: a bulk explosives detection technique based on the magnetic
properties of the hydrogen atoms within the explosive being detected.

Nuisance alarm: In trace detection, an alarm caused by the detection of explosive material, but where the detection results not from a bomb or other contraband explosives but rather from a non threat item. For example, in a portal that screens personnel for explosives, detection of NG on a heart patient using NG tablets would be a nuisance alarm. A nuisance alarm is different from a false alarm, since in the case of a false alarm no explosive material is actually present.

Oxidizer: any substance that chemically reacts with another substance to increase its oxygen content.

Particulate: contamination in the form of residual particles attached to clothing, furniture, luggage, skin, or some other surface.

Parts per billion: a quantitative measure of pressure and certain other quantities. When used in reference to explosives vapour pressures, one part per billion means that under equilibrium conditions the air above the explosive material will contain one molecule of explosive vapour for every billion molecules in the air itself.

Parts per million: a measure of explosive vapour concentration analogous to parts per billion, but a thousand times more concentrated. Thus one part per million of explosives vapour in air means one molecule of explosive vapour per every million molecules in the air itself.

Parts per trillion: a measure of explosives vapour concentration analogous to parts per billion, but a factor of one thousand less concentrated. Thus one part per trillion of explosives vapour in air means one molecule of explosive vapour per every trillion molecules in the air itself.

Pentolite: a commonly employed booster explosive, composed of 50 percent TNT and 50 percent PETN.

Percussion primer: a primer that converts mechanical energy into a flame, such as the primer that is set off by the firing pin in a gun.

PETN: pentaerythritol tetranitrate, a common high explosive. It is used in plastic explosives such as Detasheet and Semtex, and has a low vapour pressure (a few parts per trillion at room temperature and atmospheric pressure). Molecular formula C5H8N4O12; molecular weight =

PFNA: pulsed fast neutron analysis.

Phosphor: any substance that can be stimulated to emit light by incident radiation.

Picogram: one-trillionth of 1 gram, usually written as pg.

PINS: portable isotopic neutron spectroscopy.

Pipe bomb: a homemade bomb in which explosive material is packed into a section of (usually metal) pipe. Upon explosion, the pipe may shatter, and the propelled fragments thus produced can do much damage to people and property.

Pixel: the smallest resolvable spot on a computer or television screen.

Plastic explosives: high-explosive materials that have the general consistency of plastic. They are usually composed of RDX and/or PETN, along with a small amount of oil or elasticizing agent. Examples include C-4, Detasheet, and Semtex.

Portable isotopic neutron spectroscopy: a portable explosives detection system based on the emission of gamma rays when a material is bombarded with neutrons from a Cf source.

Portal: a walk-through, booth-like structure which serves the purpose of screening personnel for contraband. Examples include the metal detection portals currently deployed in airports, and various types of explosives detection portals that are now on the market or in development.

Positive-pressure phase: the brief time after a detonation in which the local pressure is much greater than atmospheric pressure, due to the outward-moving blast pressure wave.

Post-blast analysis: analysis of the site of an explosion to attempt to identify the type of explosive that was used.

Potassium chlorate: an explosive compound, KClO3.

Potassium nitrate: a crystalline compound, KNO3, used in the manufacture of explosives, pyrotechnics, and propellants.

Preconcentrator: any mechanical device designed to collect a dilute trace chemical sample and concentrate it, prior to delivery into a detector.

Prill: the loose, powder form of an explosive (as opposed to gel form) or a compressed pellet thereof. The ready made ANFO explosive is also marketed under the name “Prills.”

Primacord: a brand name for detonating cord.

Primary explosives: high-explosive compounds or mixtures that, when present in small quantities, can convert the process of deflagration into detonation. Primary explosives are used to induce detonation of a secondary explosive.

Primer: a cap or tube containing a small amount of primary explosive and used to detonate a secondary main charge.

Primex: a brand name for detonating cord.

Probability of detection – P(d): the probability that a certain EDS can detect a certain amount of a given type of explosive under a particular set of conditions. If a positive detection is always made under these conditions, the probability of detection would be 100 percent. If a detection is made only half the time, the probability of detection would be 50 percent. In general, a large number of experimental trials need to be conducted to accurately determine this parameter.

Propellants: explosive compounds or mixtures used for propelling projectiles or rockets.

Pulsed Fast Neutron Analysis: a nuclear screening technique which measures the elemental composition of the object being scanned through neutron interaction with elemental constituents of the object, resulting in characteristic gamma rays.

Pyrodex: a low-explosive material used as a filler in some improvised devices. Developed by Hodgdon Powder Company, this propellant is available in powder or pellet form. Pyrodex has 30 percent more power than common black powder.

Pyrotechnics: physical mixtures of fuel and oxidizer powders, used to produce light (e.g., fireworks), sound, heat, or smoke.

Q: quality factor, electronics-related term defining the selectivity of a resonant circuit.

QR: quadrupole resonance.

Quadrupole resonance: a bulk explosives detection technique in which the material under investigation is probed using rf radiation. This results in excitation of the nuclei of nitrogen atoms, which emit photons of a characteristic frequency when they relax. The resulting signal is specific for a certain type of nitrogen-containing compound.

Random screening: performing explosives detection on a randomly chosen fraction of a large number of people or items. For example, a security checkpoint might wish to screen every fourth person entering a secure facility. Random screening has the advantage of providing a deterrent against the illicit transport of explosives into a given area, while at the same time being less time consuming than uniform screening. RDX: a high explosive, cyclotrimethylenetrinitramine, also known as cyclonite. The abbreviation RDX stands for “research and development explosive.” RDX is the main ingredient of C-4, and is also used in Semtex. It has a low vapour pressure (low parts per trillion at room temperature and atmospheric pressure). It consists of a six-membered ring of alternating carbon and nitrogen atoms, with nitro (NO2) groups attached to the nitrogen atoms. Molecular formula C3H6N6O6; molecular weight = 222.

RF: radio frequency.

Safety fuse: a flame-producing source used in some non-electric blasting caps.

Saltpeter: potassium nitrate.

Secondary explosives: high-explosive compounds or mixtures that are generally initiated to detonation by intense shock. Secondary explosives are generally less sensitive than primary explosives, but pack more explosive power.

Secondary high-explosive boosters: explosives which provide the detonation link in an explosive train between the very sensitive primary high explosives and the comparatively insensitive main charge high explosives.

Secure area, secure facility: any area or facility where access is restricted by appropriate entry controls. Entry normally involves some form of identity verification for the entering individual. It may also include contraband screening.

Security checkpoint: any checkpoint at an entrance to a secure area that administers some sort of entry control. It may also involve screening for contraband, including explosives.

Semtex: a type of plastic explosive, normally containing both RDX and PETN.

Shaped charge: specially shaped explosive charges that are used to cut or punch holes in solid materials such as steel and concrete.

Shock wave: a sharp discontinuous pressure disturbance travelling faster than the speed of sound. A shock wave is created when a high explosive detonates.

Shrapnel: precut or preformed objects (e.g., metal fragments, nails) placed in or attached to a bomb. When the bomb explodes, these objects are hurled at high velocity, with much potential damage to people and property.

Single-energy transmission x-ray scanner: an x-ray scanner using only a single x-ray beam, in which the portion of the beam that penetrates the object under investigation is detected and used to produce the x-ray image.

Smokeless powder: an explosive material (double-base propellant) in powder form, often containing nitroglycerin (typically 40 percent by weight) as the explosive ingredient.

Sodium chlorate: an explosive compound, NaClO3.

Sodium nitrate: a chemical compound, NaNO3. It is sometimes added to dynamite to increase the oxygen content and hence improve combustion.

Specificity: the ability of a chemical analysis technique to distinguish similar chemicals from one another. The greater the specificity, the more certain the identification of a particular compound can be.

Straight dynamites: a class of dynamites containing nitroglycerin as the explosive base.

Tandem mass spectrometry: a technique of chemical analysis, also referred to as mass spec/mass spec, or simply MS/MS. Essentially, it involves sending analyte molecules through two mass spectrometers consecutively, in order to increase the specificity of the system.

Tetramino nitrate: a highly sensitive primary high explosive, which can be formed from the reaction of ammonium nitrate with brass or bronze tools.

Tetryl: a high-explosive compound, similar in structure to TNT. Molecular formula C7H5N5O8; molecular weight = 287.

Tetrytol: a military explosive composed of approximately 75 percent tetryl and 25 percent TNT.

Thermal neutron: a neutron having an energy that is typical of neutrons at room temperature.

Thermal neutron activation: a bulk explosives detection technique, in which explosives are detected by the emission of characteristic radiation (gamma rays) that occurs when the explosive material is irradiated with thermal energy neutrons.

Threat: the event or occurrence which a protective measure is intended to guard against.

Threat consequence: the results of a particular threat event occurring, including death or injury to personnel, and damage to property.

Threat item: the item that an EDS is designed to detect, i.e., a bomb or contraband explosives material.

Threat probability: the likelihood of a particular threat event actually occurring, on a scale of 0 percent (no probability of occurring) to 100 percent (certainty that the event will occur).

Throughput rate: the rate at which an EDS can process the people or objects being screened. It is generally expressed in units such as people per hour for a personnel portal, or bags per hour for an x-ray baggage scanner.

TNA: thermal neutron activation.

TNT: 2,4,6-trinitrotoluene, a common high explosive with a moderate vapour pressure (near one part per billion at room temperature and atmospheric pressure). Molecular formula C7H5N3O6; molecular weight = 227.

Tovex: a trade name for certain water-gel based explosives.

Trace explosives detection system: any EDS that detects explosive materials by collecting and identifying trace residue from the material. This residue may be in the form of either vapour or particulate. Trace detection is in contrast to bulk detection.

Two-part explosives: explosives that consist of two separate components, which are sold together in separate containers and need to be mixed together prior to detonation.

Ultraviolet light: electromagnetic radiation that is less energetic than x-rays but more energetic than visible light.

Uniform screening: Performing explosives detection on all persons or items passing through a given security checkpoint, applying the same screening process to all of them. Uniform screening is in contrast to random screening.

Vapour generator: any device designed to produce calibrated amounts of vapour of a particular compound.

Vapour pressure: the quantity of vapour (usually expressed in terms of a concentration) of an explosive compound that exists above the compound in air at equilibrium under a specified set of conditions.

Water-gel explosives: explosive mixtures (slurries) consisting of saturated aqueous solutions of ammonium nitrates and other nitrates.

Wavelength: a property of electromagnetic radiation that is inversely proportional to its energy.

Working lifetime: the time period during which a given EDS is useful. For both a canine and an IMS, a typical working lifetime might be on the order of 10 years.

X-ray absorption coefficient: the fraction of incident x-rays that is absorbed by a given material.

X-ray backscatter coefficient: the fraction of incident x-rays that is backscattered (i.e.,
reflected) by a given material.

X-rays: high-energy electromagnetic radiation with wavelength in the approximate range of 0.05 angstroms to 100 angstroms (one angstrom = 1 A = 100 billionths of one centimetre). Less energetic than gamma rays.

X-ray transmission coefficient: the fraction of incident x-rays that pass through a given material.

Z: symbol for atomic number.


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