Radiography in Modern Industry - Kodak

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Relative ExposureLog RelativeExposure1 0.05 0.702 0.3010 1.0030 1.48150 2.18Interval in Log RelativeExposure0.700.700.70This illustrates another useful property of the logarithmic scale. Figure 43 shows that theantilogarithm of 0.70 is 5, which is the ratio of each pair of exposures. Hence, to find the ratio ofany pair of exposures, it is necessary only to find the antilog of the log E (logarithm of relativeexposure) interval between them. Conversely, the log exposure interval between any twoexposures is determined by finding the logarithm of their ratio.Figure 47: Characteristic curves of three typical x-ray films, exposed between lead foilscreens.As Figure 47 shows, the slope (or steepness) of the characteristic curves is continuouslychanging throughout the length of the curves. The effects of this change of slope on detailvisibility are more completely explained in "The Characteristic Curve". It will suffice at this point togive a qualitative outline of these effects. For example, two slightly different thicknesses in theobject radiographed transmit slightly different exposures to the film. These two exposures have acertain small log E interval between them, that is, have a certain ratio. The difference in thedensities corresponding to the two exposures depends on just where on the characteristic curvethey fall, and the steeper the slope of the curve, the greater is this density difference. Forexample, the curve of Film Z (See Figure 47), is steepest in its middle portion. This means that acertain log E interval in the middle of the curve corresponds to a greater density difference thanthe same log E interval at either end of the curve. In other words, the film contrast is greatestRadiography in Modern Industry 70
where the slope of the characteristic curve is greatest. For Film Z, as has been pointed out, theregion of greatest slope is in the central part of the curve. For Films X and Y, however, the slope--and hence the film contrast continuously increases throughout the useful density range. Thecurves of most industrial x-ray films are similar to those of Films X and Y.Use Of The Characteristic CurveThe characteristic curve can be used to solve quantitative problems arising in radiography, in thepreparation of technique charts, and in radiographic research. Ideally, characteristic curves madeunder the radiographic conditions actually encountered should be used in solving practicalproblems. However, it is not always possible to produce characteristic curves in a radiographicdepartment, and curves prepared elsewhere must be used. Such curves prove adequate formany purposes although it must be remembered that the shape of the characteristic curve andthe speed of a film relative to that of another depend strongly on developing conditions. Theaccuracy attained when using "ready-made" characteristic curves is governed largely by thesimilarity between the developing conditions used in producing the characteristic curves andthose for the film, whose densities are to be evaluated.A few examples of the quantitative use of characteristic curves are worked out below. In theexamples below, D is used for density and log E for the logarithm of the relative exposure.Example 1: Suppose a radiograph made on Film Z (See Figure 48) with an exposure of 12 mAminhas a density of 0.8 in the region of maximum interest. It is desired to increase the density to2.0 for the sake of the increased contrast there available.1. Log E at D = 2.0 is 1.622. Log E at D = 0.8 is 1.003. Difference in log E is 0.62Antilogarithm of this difference is 4.2Therefore, the original exposure is multiplied by 4.2 giving 50 mA-min to produce a density of 2.0.Radiography in Modern Industry 71
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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
Page 19 and 20: Table III - Industrial Gamma-Ray So
Page 21 and 22: 1. The source of light should be sm
Page 23 and 24: B and H in the Figure 13 show the e
Page 25 and 26: Figure 14: Geometric construction f
Page 27 and 28: Figure 17: Pinhole pictures of the
Page 29 and 30: The kilovoltage applied to the x-ra
Page 31 and 32: Figure 21: Schematic diagram of som
Page 33 and 34: kind of material radiographed, the
Page 35 and 36: instance, the kilovoltage may be fi
Page 37 and 38: The technique need not be limited t
Page 39 and 40: Chapter 5: Radiographic ScreensWhen
Page 41 and 42: Contact between the film and the le
Page 43 and 44: Figure 29: The number of electrons
Page 45 and 46: lead foil screens ran be retained w
Page 47 and 48: Figure 33: The sharpness of the rad
Page 49 and 50: Figure 34: Low density (right) is a
Page 51 and 52: such as a wall or floor, on the fil
Page 53 and 54: from this source. Since scatter als
Page 55 and 56: A filter reduces excessive subject
Page 57 and 58: Definite rules as to filter thickne
Page 59 and 60: 0.010-inch front screen of value be
Page 61 and 62: Example: Suppose that with a given
Page 63 and 64: If the milliamperage remains consta
Page 65 and 66: espectively. In other words, a cons
Page 67 and 68: Any given exposure chart applies to
Page 69: Figure 46: Typical gamma-ray exposu
Page 73 and 74: Figure 49: Characteristic curves of
Page 75 and 76: Figure 51: Characteristic curve of
Page 77 and 78: Nomogram MethodsIn Figure 54, the s
Page 79 and 80: Figure 56: Transparent overlay posi
Page 81 and 82: Figure 58: Overlay positioned so as
Page 83 and 84: The problem of radiographing a part
Page 85 and 86: Figure 62: System of lines drawn on
Page 87 and 88: Chapter 8: Radiographic Image Quali
Page 89 and 90: Film contrast refers to the slope (
Page 91 and 92: Hole Type PenetrametersThe common p
Page 93 and 94: of the same thickness as the specim
Page 95 and 96: Chapter 9: Industrial X-ray FilmsMo
Page 97 and 98: Figure 70 indicates the direction t
Page 99 and 100: the lead letters on a radiation-abs
Page 101 and 102: Therefore, protection requirements
Page 103 and 104: 5. Avoid pressure damage caused by
Page 105 and 106: Paddles or plunger-type agitators a
Page 107 and 108: slow, and the development time reco
Page 109 and 110: ubbles make their way to the surfac
Page 111 and 112: When development is complete, the f
Page 113 and 114: soften considerably with prolonged
Page 115 and 116: Figure 77: The roller transport sys
Page 117 and 118: Rapid Access to Processed Radiograp
Page 119 and 120: 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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The radiograph exposed in the right
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To illustrate, let us assume that t
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Figure 95: High-speed x-ray picture
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Figure 97: Two methods of neutron r
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Duplicating RadiographsSimultaneous
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Sometimes, as when sets of referenc
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PhotofluorographyIn photofluorograp
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discontinuities or of segregation i
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from the camera or by reaching down
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Figure 106: Schematic diagram of th
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valuable technique, for instance, i
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The position of the spots is determ
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Powder Diffraction File, Internatio
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Processing TechniquesRadiographs on
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Since this formula applies only to
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such that it does not distort the i
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Figure 113: A: Representation of a
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Figure 115: Characteristic curve of
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film fairly well. If high densities
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Density = 1.5 Density = 2.5Film Rel
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In most industrial radiography, the
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e noted here. Although the average
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Chapter 17: Film Graininess; Signal
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The ratio of signal to noise has a
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Chapter 18: The Photographic Latent
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Thus, the change that makes an expo
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Figure 130: Stages in the developme
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electrons by successive Compton int
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Development is essentially a chemic
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Chapter 19: ProtectionOne of the mo
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duct is brought into the x-ray room
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