Radiography in Modern Industry - Kodak

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Figure 129: "Plain view" of a layer of ions of a crystal similar to that of the previous figure.A latent-image site is shown schematically, and two interstitial silver ions are indicated.The Gurney-Mott theory envisions latent-image formation as a two-stage process. It will bediscussed first in terms of the formation of the latent image by light, and then the specialconsiderations of direct x-ray or lead foil screen exposures will be covered.The Gurney-Mott TheoryWhen a photon of light of energy greater than a certain minimum value (that is, of wavelengthless than a certain maximum) is absorbed in a silver bromide crystal, it releases an electron froma bromide (Br-) ion. The ion, having lost its excess negative charge, is changed to a bromineatom. The liberated electron is free to wander about the crystal (See Figure 130). As it does, itmay encounter a latent image site and be "trapped" there, giving the latent-image site a negativeelectrical charge. This first stage of latent-image formation--involving as it does transfer ofelectrical charges by means of moving electrons--is the electronic conduction stage.Radiography in Modern Industry 202
Figure 130: Stages in the development of the latent image according to the Gurney-Motttheory.The negatively charged trap can then attract an interstitial silver ion because the silver ion ischarged positively (See Figure 130C). When such an interstitial ion reaches a negatively chargedtrap, its charge is counteracted, an atom of silver is deposited at the trap, and the trap is "reset”(See Figure 130D). This second stage of the Gurney-Mott mechanism is termed the ioniccondition stage, since electrical charge is transferred through the crystal by the movement ofions--that is, charged atoms. The whole cycle can recur several, or many, times at a single trap,each cycle involving absorption of one photon and addition of one silver atom to the aggregate.(See Figure 130, E to H)In other words, this aggregate of silver atoms is the latent image. The presence of these fewatoms at a single latent-image site makes the whole grain susceptible to the reducing action ofthe developer. In the most sensitive emulsions, the number of silver atoms required may be lessthan ten.Radiography in Modern Industry 203
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RadiographyinModernIndustry
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RadiographyinModernIndustryFOURTH E
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ContentsIntroduction...............
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Chapter 1: The Radiographic Process
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Intensifying ScreensX-ray and other
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makes it a very suitable material f
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Figure 6: Typical voltage waveforms
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Table I - Typical X-ray Machines an
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The wavelengths (or energies of rad
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Table III - Industrial Gamma-Ray So
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1. The source of light should be sm
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B and H in the Figure 13 show the e
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Figure 14: Geometric construction f
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Figure 17: Pinhole pictures of the
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The kilovoltage applied to the x-ra
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Figure 21: Schematic diagram of som
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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Figure 70 indicates the direction t
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the lead letters on a radiation-abs
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Therefore, protection requirements
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5. Avoid pressure damage caused by
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Paddles or plunger-type agitators a
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slow, and the development time reco
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ubbles make their way to the surfac
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When development is complete, the f
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soften considerably with prolonged
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Figure 77: The roller transport sys
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Rapid Access to Processed Radiograp
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Figure 78: Film-feeding procedures
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Chapter 11: Process ControlUsers of
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3. Age of the developer replenisher
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Figure 80: Control chart below for
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DiscussionDensitometric data and pr
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Figure 82: Plan of a manual x-ray p
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Figure 83: A schematic diagram of a
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loading-bench activities are carrie
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KODAK Quinone-Thiosulfate Intensifi
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Methylene-Blue MethodTwo variations
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KODAK Hypo Test Solution HT-2Avoird
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In summary, use of the test papers
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narrow angle would be very thick, e
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When radiation passes through a spe
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Figure 89: Demonstration of the eff
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Figure 90: The amount of gamma radi
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Page 153 and 154: To illustrate, let us assume that t
Page 155 and 156: Figure 95: High-speed x-ray picture
Page 157 and 158: Figure 97: Two methods of neutron r
Page 159 and 160: Duplicating RadiographsSimultaneous
Page 161 and 162: Sometimes, as when sets of referenc
Page 163 and 164: PhotofluorographyIn photofluorograp
Page 165 and 166: discontinuities or of segregation i
Page 167 and 168: from the camera or by reaching down
Page 169 and 170: Figure 106: Schematic diagram of th
Page 171 and 172: valuable technique, for instance, i
Page 173 and 174: The position of the spots is determ
Page 175 and 176: Powder Diffraction File, Internatio
Page 177 and 178: Processing TechniquesRadiographs on
Page 179 and 180: Since this formula applies only to
Page 181 and 182: such that it does not distort the i
Page 183 and 184: Figure 113: A: Representation of a
Page 185 and 186: Figure 115: Characteristic curve of
Page 187 and 188: film fairly well. If high densities
Page 189 and 190: Density = 1.5 Density = 2.5Film Rel
Page 191 and 192: In most industrial radiography, the
Page 193 and 194: e noted here. Although the average
Page 195 and 196: Chapter 17: Film Graininess; Signal
Page 197 and 198: The ratio of signal to noise has a
Page 199 and 200: Chapter 18: The Photographic Latent
Page 201: Thus, the change that makes an expo
Page 205 and 206: electrons by successive Compton int
Page 207 and 208: Development is essentially a chemic
Page 209 and 210: Chapter 19: ProtectionOne of the mo
Page 211 and 212: duct is brought into the x-ray room
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