Radiography in Modern Industry - Kodak

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intimate contact. In particular, the pressure supplied by a conventional spring-backed cassettemay be insufficient to produce adequate contact if the specimen--for instance, a leaf or a wrinkledpiece of stiff paper--is not itself flat.A method related to electron radiography is electron-emission radiography--sometimes referred toin Europe as "reflection microradiography." This method is based on the fact that electronemission from a substance exposed to x-rays depends on the atomic number of the material,among other factors. When a photographic or radiographic film is placed in intimate contact with aspecimen and the whole irradiated from the film side with hard x-rays such as are used inelectron radiography, differences in electron emission resulting from differences in atomic numberand variations in concentration of components are recorded on the developed film, as is shown inFigure 107.Figure 107: Schematic diagram of the technique for making electron-emissionradiographs. More electrons are emitted from the areas of the specimen that containmateials of high atomic number. (For illustrative clarity, the electron paths have beenshown as straight and parallel; actually, the electrons are emitted diffusely.)Hard x-rays are required in this technique for the same reason as in electron radiography: It isnecessary to maximize the ratio between the electron exposure, which produces the image, andthe uniform overall exposure produced by the direct x-rays.Specimens to be examined by electron-emission radiography need to be smooth and plane onone side only and can be quite massive--significant factors when the specimen cannot be cut.An electron-emission radiograph resembles a photomicrograph in that it shows details only of thesurface of a specimen whereas microradiography shows the distribution of a componentthroughout the thickness of the specimen. For this reason, and because electron emission is lesssensitive to differences in atomic number than is soft x-ray absorption, an electron-emissionradiograph of a specimen contains markedly less information than a microradiograph of a thinsection of the same specimen.Image definition is also poorer than in a microradiograph because of the diffuse emission ofelectrons from the surface and because of the increased graininess of the film associated with thehigh-energy x-ray and electron exposures. Nevertheless, electron-emission radiography is aRadiography in Modern Industry 170
valuable technique, for instance, in the examination of printed matter to distinguishnondestructively between inks containing metallic pigments and those containing aniline dyes.The photographic materials used for microradiography are also useful for electron-emissionradiography. However, the maximum enlargements possible are considerably less than thoseattained in microradiography with the same film because of the diffuse nature of the electronemission and the greater graininess. As in the case of electron radiography, the back emulsion ofa double-coated film should be protected from the action of the developer or it should be removedafter processing (See "Removal Of One Emulsion From Double-Coated Film").It is necessary to insure good contact between specimen and film because of the diffuse emissionof the electrons that produce the image. In the case of small specimens, a vacuum cassette, intowhich both specimen and film can be put, is very useful.Figure 108: Bavarian stamp of 1920 (Scott No. O52). A: Photograph. The design is greenand the"Deutsches Reich" overprint is black. B: Soft x-ray radiograph. Details of bothdesign and paper are visible. Design is "negative," indicating absorption of the x-rays bythe ink. C: Electron radiograph. Only the details of the paper are shown. D: Electronemissionradiograph. The design is "positive," indicating a relatively high electronemission from some heavy element in the ink. The overprint cannot be seen.The three techniques--soft x-ray radiography (microradiography), electron radiography, andelectron-emission radiography--can be compared using the postage stamp (See Figure 108A) asa specimen. The design of the stamp is green and the "Deutsches Reich" overprint is black.Figure 108B above is a soft x-ray radiograph, which could be greatly enlarged if necessary,showing details of both design and paper. The image of the design is a negative indicating theabsorption of the x-radiation by the ink. The electron radiograph (See Figure 108C) was madewith the design of the stamp away from the recording film, and contains details of the paperstructure only. The "wavy line" watermark shows very clearly. The electron-emission radiograph(See Figure 108D) shows the details of the design alone, indicating that the green ink has a highelectron emission and hence that it contains a metallic pigment, rather than aniline dye. No traceof the black overprint is visible because the carbon-based ink has negligible electron emission.Radiography in Modern Industry 171
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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
Page 119 and 120: Figure 78: Film-feeding procedures
Page 121 and 122: Chapter 11: Process ControlUsers of
Page 123 and 124: 3. Age of the developer replenisher
Page 125 and 126: Figure 80: Control chart below for
Page 127 and 128: DiscussionDensitometric data and pr
Page 129 and 130: Figure 82: Plan of a manual x-ray p
Page 131 and 132: Figure 83: A schematic diagram of a
Page 133 and 134: loading-bench activities are carrie
Page 135 and 136: KODAK Quinone-Thiosulfate Intensifi
Page 137 and 138: Methylene-Blue MethodTwo variations
Page 139 and 140: KODAK Hypo Test Solution HT-2Avoird
Page 141 and 142: In summary, use of the test papers
Page 143 and 144: narrow angle would be very thick, e
Page 145 and 146: When radiation passes through a spe
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149 and 150: Figure 90: The amount of gamma radi
Page 151 and 152: The radiograph exposed in the right
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: Figure 106: Schematic diagram of th
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 and 202: Thus, the change that makes an expo
Page 203 and 204: Figure 130: Stages in the developme
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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Radiography in Modern Industry - Kodak

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