Varian Linatron High-Energy X-ray Applications 2007

LINEAR ATTENUATION COEFFICIENT
Constant used to describe the degree of x-ray attenuation
per unit path length in a specified material. It is a function
of x-ray energy and is usually expressed in units of
reciprocal inch or centimeter.
MAGNIFICATION
Degree of projection and enlargement of regions of the
object being radiographed in the developed film that result
from the choice of distances between the source, object,
and film in the radiography setup.
NARROW BEAM
(See BROAD BEAM)
NDT
An acronym of NONDESTRUCTIVE TESTING, and
the name given to a test, inspection, or examination of
materials to determine specific properties or characteristics,
or to locate defects without causing damage to the object
under test.
PENETRAMETER
Same as IQI.
PAIR PRODUCTION
An absorption process for photons of energies greater than
1.02 MeV, in which the photon transforms into a pair of
particles (an electron and a positron).
PHOTOELECTRIC ABSORPTION
An absorption process for photons of energies under
1 MeV in which the photon loses all of its energy to an
atomic electron. The electron leaves its atomic orbit and
continues to move though the material.
RAD
Unit of radiation dose; 1 rad equals the absorption of 100
ergs of (any form of) radiation per gram of absorbing
material.
RADIOGRAPHIC COVERAGE
That section and area of the object that is radiographed,
exposed and imaged on the x-ray film. The
RADIOGRAPHIC COVERAGE is usually stated as part
of the specifications for the radiography work.
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REAL-TIME IMAGING
X-ray radiography that produces instantaneous and
continuous images on a TV monitor. The images obtained
can be electronically processed to enhance their quality,
and can be recorded (e.g., on videotape) for later playback.
ROENTGEN
Unit of radiation exposure (the ability of an x-ray beam to
ionize air) corresponding to producing 1.610 x 1012 ion
pairs per gram air.
SCATTER mRADIATION
Secondary x-rays and electrons produced whenever a
primary x-ray beam irradiates an object. Also includes
objects not being examined such as the floor, walls, tables,
etc. Secondary radiations are emitted in all directions, and
are of lower energy than the primary rays.
SENSlTIVITY
Refers to the degree to which images of wires (Wire
Sensitivity), drilled holes in plaques (Plaque Sensitivity),
steps (Contrast or Thickness Sensitivity), and actual defects
in materials (Radiographic Sensitivity) are displayed and
capable of being discerned in an x-ray film or other
imaging device. Sensitivity is usually expressed as a
percentage of the thickness of the object being examined.
SOURCE-TO-FILM DISTANCE
The actual distance between the focal spot of the x-ray
source and the plane of the x-ray film in the specific
exposure. This distance affects the amount of exposure
used in every application of radiography.
22˚ PYRAMID
Refers to the size and shape of the collimator used in the
Linatron Model 200A, 400 and 1000. The collimator
provides a cone (four-sided pyramid) of radiation with the
focal spot as apex, the base a square, and with the sides
forming a 22˚ interior angle.
Varian Linatron applications