Varian Linatron High-Energy X-ray Applications 2007

D/T RATIO
Ratio of the distance between the source (Linatron target)
and the front surface of the object being radiographed to
the distance from the front surface of the object to the film
(usually the object thickness).
DEFECTS
Usually discontinuities and imperfections in the object
being examined, considered deleterious to the service of the
object, and which are revealed in Linatron radiography.
Depending on the object and service requirements, Voids,
Gaps, Separations, Cracks, Misassemblies, and other
homogeneities may be identified as DEFECTS in a
specification. (See Table 5-2, p. , also Table 5-3, p. )
DEFINITION
Fidelity in x-ray film images of sharp edges of the object,
and the degree with which the detail of small defects and
discontinuities are clearly shown. (See also:
UNSHARPNESS)
DENSITY (Film)
Degree of blackening of the exposed and developed x-ray
film; DENSITY is usually expressed in terms of the H&D
scale. (See H&D UNIT)
DENSITY (Film) GRADIENT
Amount of density change in the exposed and developed
film per unit of change in the logarithm of the exposures.
Film manufacturers also refer to density Gradient as the
GAMMA ( y ) of the film at the particular density
specified.
DIFFERENTIAL ABSORPTION
Differences in the x-ray absorption (and therefore the
transmission through) various adjacent sections of an
object being radiographed, which result in differences in
the exposure to the film behind those areas.
EDGE ENHANCEMENT
TV scanning and electronic processing of radiographic
(Real-Time or Film) images, that produce highlighting of
edges of the object, defects, etc., in the final image. The
resulting processed (edge-enhanced) images are displayed
on a TV monitor.
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ELECTRON EQUILIBRIUM
Occurs in an x-ray measurement arrangement when, for
electrons (set in motion by the x-rays) leaving the
measuring cavity, electrons of equal total energy enter.
ELECTRON LINEAR ACCELERATOR
A system containing an electron source, power supply,
accelerator section, and metal target (when x-rays are to be
produced). The system generates high-energy x-rays by
accelerating the electrons to high energies and by directing
the electrons in a linear path to collide with the metal target
which results in producing x-rays.
ENERGY SPECTRUM (Photon)
Distribution of x-ray intensity (or quantity of x-ray
photons) as a function of the x-ray energy in an x-ray
beam.
EXPOSURE CURVE
Plot of the exposure Rads vs material thickness, that gives
the exposure conditions to obtain a radiograph with
specific film density.
FIELD COVERAGE
Size of the area that can be exposed in a single radiographic
exposure, for a particular source, collimator, and
distance from the x-ray target.
FIELD FLATNESS
Degree of constancy of radiation intensity level across the
field of an x-ray beam usually measured in a plane normal
to the beam central axis.
FIELD HALF-WIDTH
Distance measured at the film plane outward from the
central ray of the x-ray beam, to the outer edge of the x-ray
beam.
FILM CHARACTERISTIC CURVE
Plot of the relationship between exposure time and image
density for a specific film and exposure strength. This term,
in practice, is used only by the film manufacturer as one
specification of the film’s properties. Film users who make
measurements to determine this relationship with their xray
source, exposure procedure, and film processing, refer
to their results as: FILM RESPONSE CURVES.
Varian Linatron applications