Understanding Neutron Radiography

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The Magical Book of <strong>Neutron</strong> <strong>Radiography</strong> Charlie Chong/ Fion Zhang
Charlie Chong/ Fion Zhang
Page 1 and 2: Understanding Neutron Radiography R
Page 3: Submarine Nuclear Pile Charlie Chon
Page 7 and 8: 3. Techniques/Calibrations • Bloc
Page 9 and 10: Charlie Chong/ Fion Zhang
Page 11 and 12: Greek Alphabet sound A a [a] nu B [
Page 13 and 14: A Alpha r Gamma NNu T Tau (al-fah)
Page 15 and 16: INTRODUCTION Radiography with neutr
Page 17 and 18: 1. PRINCIPLES AND PRACTICE OF NEUTR
Page 19 and 20: He had indentified a particle which
Page 21 and 22: BEPO stood for British Experimental
Page 23 and 24: They also demonstrated the applicat
Page 25 and 26: The radiographic process requires f
Page 27 and 28: 1.1.3. Neutron Sources Neutrons are
Page 29 and 30: This energy varies with both the ta
Page 31 and 32: The reaction takes place, that is a
Page 33 and 34: The life and output of the target u
Page 35 and 36: There is considerable variation in
Page 37 and 38: 1 .1 .3.2 Radioisotopes Radioisotop
Page 39 and 40: Fig. 1 .3 Isotopie Neutron Sources.
Page 41 and 42: Table 1.2 Radioisotopic Neutron Sou
Page 43 and 44: The nuclear reactor is an assembly
Page 45 and 46: or Cf 252 (spontaneous fission) //
Page 47 and 48: Neutron Source- Reactor .. "J ' ' '
Page 49 and 50: The Nuclear Chain Reaction Cs Neutr
Page 51 and 52: Source Radioisotopes, accelerator N
Page 53 and 54: Cf 252 (spontaneous fission) 1.0 af
Page 55 and 56:
Spontaneous fission (SF) NucUde Hal
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Figure 2: Spontaneous Fission Spect
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This fission process produces a con
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Keywords: • effective multiplicat
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Fig. 1.5 Increase in Neutron Flux a
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Table 1.3 Summary of the Properties
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The unit of cross section is the 'b
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Charlie Chong/ Fion Zhang 10 4 10
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One isotope of cadmium, 113 Cd, abs
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This is given by -dФ /dx = ФσN (
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The ratio between these two neutron
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Neutron Attenuation Incident lntens
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PART 5 NEUTRON CROSS SECTIONS AND A
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For photons: I = I o e -μx t For N
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If on the other hand, the material
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Charlie Chong/ Fion Zhang σ C σ H
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FIGURE 10. Half-Value Layers of Sel
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5.2 Half-Value Layers An important
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5.4 CONCLUSION Neutron radiography
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A prime requirement for a moderator
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1.1.4.3 Collimation Having produced
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An alternative method, widely used
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Charlie Chong/ Fion Zhang A. MULn-'
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As the flux gradient is usually sma
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Now the fraction of neutrons lost d
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for simplicity this can be expresse
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Hawkesworth found reasonable agreem
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To minimise unsharpness the apertur
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(f) the resolution improves with an
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Neutron generator Neutron collimato
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1 .1 .5 Neutrons Applied to Radiogr
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Neutrons will penetrate the body of
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Neutrons radiograph. I eutt·on(Gd/
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Neutrons radiograph. Charlie Chong/
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Neutrons radiograph Charlie Chong/
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100 I Ill 100 .. N E 10 u Ī- z w -
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Attenuation Coefficients for Neutro
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1 . 1 .6 Neutron Image Detectors Un
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The particular a dvantage of the ga
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Figure 2: (a) Silver Activated zinc
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1.1 .6.2 Transfer Technique This me
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With the transfer method only the f
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Fig. 1.10 Irradiation /Transfer Cur
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Table 1.4 The Characteristics of So
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1.1 .6.3 Dynamic Imaging Methods Th
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Fig. 1.11 Television System for Neu
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1.1.7 Image Recorders At present th
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Development, on the other hand, pro
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The relationship between exposure a
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Fig. 1.12 Typical Characteristic Cu
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The steeper the slope of the curve
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Type Kodak Ltd. (U .K.) IIford Ltd
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Farny [Ref. 36] has made the follow
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■ (a) (b) (c) (d) (e) (f) (g) Ind
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1. 1 .8 Film and Foil Relationships
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The literature often describes meth
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Fig. 1 . 1 3 Measu rement of Unshar
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There are three types of unsharpnes
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This is a frequence response method
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This resolution is at the expense o
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Fig. 1 . 1 5 Contrast Transfer Func
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Ф = Ф o e -Σx where Ф = transmi
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For a metal foil detector D e = G
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Hawkesworth [Ref. 23] considered th
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Furthermore thermal neutrons are at
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1. 1 .9 Neutron Beam Filters Neutro
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(a) (b) (c) the ratio of 1 .4 eV ne
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Fig. 1 . 1 6 Resonance Curves for a
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1) J KEY TO RESONANCE TYPES A 8 c 0
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1.2 THE DESIGN OF NEUTRON RADIOGRAP
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Let us assume that your resolution
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Fig. 1.17 Van Der Graaff Accelerato
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The Van De Graaff Accelerator. Char
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Neutron Source: Linac Charlie Chong
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Neutron Source: Accelerator . I ' r
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1 .2.2 The Collimator 1 .2.2.1 Coll
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The L/D ratio of the collimator can
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Cadmium ratio - the ratio of the re
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Fig. 1.16 Resonance Curves for a Cd
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1) J KEY TO RESONANCE TYPES A B c 0
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1 .2.2.2 Characteristics of Lining
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Cadmium is readily available in foi
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106 '1017 108 10'9 11110 1 11 1 111
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Table 1.9 shows that the natura l m
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Isotopic Composition Emission Trans
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The appropriate thicknesses can be
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1 .2.2.5 Geometric Enlargement and
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- Characteristics of Indium Indium
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Table 1.10 Data on Indium [Refs. 24
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- Characteristics of Dysprosium Dys
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1 Isoto pi ~c Compo:sition l.sotopi
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Table1 .12 Data on Gadolinium [Refs
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1 .2.3.2 Converter- Foil Thickness
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Fig. 1.18 Film Foil Geometry. EMULS
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So theoretically the unsharpness is
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Now, ignoring self-shielding, equat
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For the transfer data the foils wer
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Table 1. 14 Resolut ion Characteris
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Fig. 1.19 Build-Up of Activity i n
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1 .2.3.3 Film and Foil Resolution B
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Hot Charcoal Iron Charlie Chong/ Fi
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1 .3 A PPLICATIONS OF NEUTRON RADIO
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Fig. 1.20 Cross-Section of Pressure
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Fig. 1.21 Neutron Radiographs showi
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The detection technique is non-dest
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1.3.2 Industrial Applications Hydro
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Brazing and soldering meterials are
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Run-out on deep drilled holes occur
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F ig. 1. 25 X- Radiograph and Neutr
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1 .3.4 Other Applications Figure 1.
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Charlie Chong/ Fion Zhang http://ww
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• absorption coefficient: related
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• contrast agent: a material adde
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TABLE I. NeLib'ons Crasslrfled AA;c
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More Reading: (epithermal neutron)
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Neutron capture cross section for 1
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Maxwell-Boltzmann distribution In p
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Probability density function a=l 0"
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The Maxwell-Boltzmann distribution
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• filtered neutron beam: neutron
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• indirect exposure imaging: in t
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More reading on Mass absorption coe
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• neutron radiography: a process
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• sub-thermal neutrons:neutrons h
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Nuclei or Macroscopic Cross Section
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Nuclei or Maeto6CGpiC Cr066 Section
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where N =number density of stable i
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The required film density can be de
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N (number of nuclei cm -3 ) = ρN a
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Example of cellulose acetate C 6 H
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Charlie Chong/ Fion Zhang TABLE 9.
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Further Reading: Interesting Form h
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Peach - 我爱桃子 Charlie Cho
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Good Luck Charlie Chong/ Fion Zhang
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Understanding Neutron Radiography

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