A radiographic technique to measure tissue density by measuring the amount of absorbed radiation.

One use is to detect bone loss in the spine and hips.

1. A stream of electrons emitted from a given source and traveling under the influence of an electric or magnetic field in the same direction and at approximately the same speed.
2. A stream of electrons, or electricity, that is directed towards a receiving object.
3. A narrow stream of electrons moving in the same direction, all having about the same velocity.

The electron beam of the super-microscope has become a basic tool in the research of diseases.

1. The process by which high-energy, high-current electron beams are transported from an accelerator through a medium of high-pressure gas directly to an intended target.
2. A device used in atomic physics to produce highly charged ions by bombarding atoms with a powerful electron beam.
3. The technique of transporting high-energy, high-current electron beams from an accelerator to a target through a region of high-pressure gas by creating a path through the gas where the gas density may be temporarily reduced.

The gas may be ionized; or a current may flow whose magnetic field focuses the electron beam on the target.

Ultrafast computed tomography done with a scanner in which the patient is surrounded by a large circular anode that emits X-rays as the electron beam is guided around it.

1. A device; such as, a klystron, in which the velocity of an electron beam is kept at a constant level in order to produce exceedingly high radio frequencies.
2. Velocity-modulated generator, such as a klystron tube (type of vacuum tube used as an amplifier), used to generate extremely high radio frequencies.

A klystron is an evacuated electron-beam tube in which an initial velocity modulation imparted to electrons in the beam results subsequently in density modulation of the beam. A klystron is used either as an amplifier in the microwave region or as an oscillator.

A process using a stream of electrons to heat and to bond two conductors within a vacuum.

1. The process of boring tiny holes into a material; such as, a ferrite or semiconductor, with a tightly focused electron beam.
2. Drilling of tiny holes in a ferrite, semiconductor, or other material by using a sharply focused electron beam to melt and evaporate or sublimate the material in a vacuum.

1. An evaporation technique in which the evaporant is heated with electron bombardment.
2. An electronic transducer, either fixed or adjustable, that reduces the amplitude of a wave without causing significant distortion.

Electron beam evaporation is a commonly used process for coating lenses and filters with anti-reflection, scratch-resistant or other specialized coatings.

The process is also commonly used for coating insulating and resistor films on electronic components.

1. A process in which strong electron beams implode tiny pellets of deuterium and tritium, causing them to attain the temperature and density needed to initiate a fusion reaction.
2. The use of intense beams of electrons to implode small pellets of deuterium and tritium so that they reach the temperature and density required for initiating a fusion reaction.

A device generally used in a cathode-ray or camera tube to emit a stream of electrons moving at uniform velocity in a straight line.

It consists of an emitting cathode and an anode, with an aperture for passage of some of the electrons.

A tool in which a beam of electrons is deflected by an electric or magnetic field (or both).

Usually the beam is made to strike a fluorescent screen so the deflection can be observed.

1. A source of multiple charged heavy ions used by a highly energized electron beam to ionize injected gas.
2. A source of multiple charged heavy ions which uses an intense electron beam with energies of five to ten kiloelectronvolts to successively ionize injected gas.

A semiconductor laser in which the electron beam that provides pumping action in a thin plate of cadmium sulfide or other material is swept electrically in two dimensions by a deflection yoke, much as in a cathode-ray tube.

The resulting laser output beam moves correspondingly, to provide high-speed scanning for data retrieval and imaging applications.

The beam can be electronically blanked, unblanked, or modulated with analog video signals for the projection of picture or other graphic data.

1. Lithography in which radiation-sensitive film is exposed to an electron beam.
2. The practice of scanning a beam of electrons in a patterned fashion across a surface covered with a film called the resist, exposing the resist, and of selectively removing either exposed or non-exposed regions of the resist called, "developing".
3. Lithography in which the radiation-sensitive film or resist is placed in the vacuum chamber of a scanning-beam electron microscope and exposed by an electron beam under digital computer control.

After exposure, the film is removed from the vacuum chamber for conventional development and other production processes.

1. A process in which controlled electron beams are used to weld or to shape a piece of material.
2. A machining process which takes place in a vacuum.

Heat is produced by a focused and controlled electron beam at a sufficiently high temperature to volatilize and so to remove metal in a specified manner.

Drilling and cutting are examples of specific applications.

1. An instrument that measures the magnetic intensity of a magnetic field according to the movement and intensity of an electron beam, which passes through the field.
2. An instrument which measures the intensity and direction of magnetic forces by the immersion of an electron beam into the magnetic field.

A melting process which takes place in a vacuum, the heat being produced by a focused electron beam.

It's used principally for refining metals to a higher degree of purity than is possible with conventional vacuum-melting techniques.

Its chief advantage is the ability to control the temperature of the molten material and the time it remains melted because both affect the degree of volatilization of impurities.

Volatilization is the conversion of a chemical substance from a liquid or solid state to a gaseous or vapor state by the application of heat, by reducing pressure, or by a combination of these processes. It is also known as vaporization.

A form of discharge produce by a perforated-wall hollow cathode operating under conditions of pressure, voltage, and geometry which is usually associated with the abnormal glow discharge.

1. A device that boosts a signal by varying the energy pumped from an electrostatic field into an electron beam traveling down the length of a tube, and then manipulating the beam at either end of the tube.
2. A parametric amplifier in which energy is pumped from an electrostatic field into a beam of electrons traveling down the length of the tube, and electron couplers impress the input signal at one end of the tube and translate spiraling electron motion into electric output at the other end.

1. A process in which an electron beam provides the energy necessary to move the majority of electrons in a semiconductor out of a ground condition.
2. The use of an electron beam to produce excitation for population inversion and lasing action in a semiconductor laser.

1. An instrument in which an electron beam places signals or data on film in a vacuum chamber.
2. A recorder in which a moving electron beam is used to record signals or data on to photographic or thermoplastic film in a vacuum chamber.
3. A device that transfers computer data onto microfilm using an electron beam.

The recording of the information contained in a modulated electron beam onto photographic or silicon resin-coated materials.

1. An instrument; such as, a klystron (type of vacuum tube used as an amplifier), oscilloscope tube, or television picture tube, which functions through the generation of one or more electron beams.
2. An electron tube whose performance depends on the formation and control of one or more electron beams.

1. The process of using a focused beam of electrons to heat materials to the fusion point.
2. A process in which a welder generates a stream of electrons traveling at up to 60 percent of the speed of light as it focuses the beam to a small, precisely controlled spot in a vacuum, and converts the kinetic energy into an extremely high temperature on impact with the piece being worked on.
3. A welding process which takes place in a vacuum.

Heat is produced by a focused electron beam that can produce welds having depth-to-width ratios of up to twenty to one.

Applications include welding of thin metal foils to thicker metal without burning, sealing of metal cans containing uranium fuel elements for reactors, and direct fusion welding of ceramic objects.

1. A narrow stream of electrons moving in the same direction under the influence of an electric or magnetic field.
2. A stream of electrons, emitted by a single source, which move in the same direction, and at the same speed.
3. A stream of electrons which can "write" on phosphor surfaces; such as, a CRT screen expose photoresistent-coated semiconductor wafers by direct writing or exposure through a mask, or magnify objects by passing through magnetic "lenses".

It can also be a cutting tool.

A cathode-ray tube, or CRT, produces images when its phosphorescent surface is struck by electron beams.

In nuclear energy, a method of internal confinement fusion in which an energy beam of electrons or other particles is directed onto a tiny pellet of a deuterium-tritium mixture, causing it to explode like a miniature hydrogen bomb, fusing the deuterium and tritium nuclei within a time span too short for them to repel each other.

1. The use of a beam of high-energy ions to remove foreign or undesirable materials from a surface.
2. Use of a high-velocity ion beam to remove material from a surface.

1. A magnet mounted to the neck of a kinescope to prevent ions from striking the kinescope screen.
2. A system that prevents an ion spot from forming on a cathode-ray tube screen, generally by using a magnetic field to divert the beam. 3. An arrangement whereby ions in the electron beam of a cathode-ray tube are prevented from bombarding (hitting with high-energy particles) the screen and producing an ion spot, usually employing a magnet to bend the electron beam so that it passes through the tiny aperture of the electron gun, while the heavier ions are less affected by the magnetic field and are trapped inside the gun.

A metal electrode, usually of titanium, into which ions from an ion pump are attracted or absorbed.

The separation of ions according to their mass is accomplished with static magnetic fields, time-varying electric fields, or methods that clock the speeds of ions having the same energies—the time-of-flight method.

Static electric fields cannot separate ions by their mass but do separate them by their energy and so provide an important design element by functioning as an energy filter.

In ion-beam machining, a stream of charged atoms (ions) of an inert gas; such as, argon, is accelerated in a vacuum by high energies and directed toward a solid workpiece.

The beam removes atoms from the workpiece by transferring energy and momentum to atoms on the surface of the object.

When an atom strikes a cluster of atoms on the workpiece, it dislodges between 0.1 and 10 atoms from the workpiece material.

Ion-beam machining, IBM, permits the accurate machining of virtually any material and is used in the semiconductor industry and in the manufacture of aspheric lenses.

The technique is also used for texturing surfaces to enhance bonding, for producing atomically clean surfaces on devices; such as, laser mirrors, and for modifying the thickness of thin films and membranes.

1. The bombardment of a substance with high-energy ions so as to cause the intermixing of atoms of two different phases in the near-surface region.
2. A process in which bombardment of a solid with a beam of energetic ions causes the intermixing of atoms of two separate phases originally present in the near-surface region.

1. The process of analyzing the mass spectrum of an ion beam in a mass spectrometer either by changing the electric or magnetic fields of the mass spectrometer or by moving a probe.
2. The process by which the mass spectrum of an ion beam is analyzed, generally by altering the electric or magnetic fields or by moving a probe in a mass spectrometer.

1. Treatment in which doctors use nuclear technology and magnets to fire protons into tumors at about two thirds the speed of light.

Proton therapy's promise lies in its ability to destroy cancerous cells while sparing healthy cells half a millimeter away, reducing side effects. It also allows doctors to ramp up the radiation dose, theoretically improving cure rates.

The precise targeting is possible because the subatomic particles release the bulk of their destructive energy beneath the skin, at the tumor's depth, rather than near the surface, as X-rays do; and while standard radiation tends to cause damage to healthy tissues on the far side of tumor, protons slow and stop as they release their energy pulse, eliminating a harmful exit dose.

2. A precise form of radiation treatment for cancer and other conditions.

It is said to minimize damage to healthy tissue and surrounding organs, and such proton treatment is considered to be highly successful and it results in fewer side effects.