1.
The Nature of
Radiation
January 10, 2001
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2.
Learning Objectives
Know basic constituents of the atom
Define and give an examples of:
Isotopes
Nuclides
Radionuclides
Radioisotopes
Radiations
Know major radiation interactions in
matter
Become familiar with and use
equations to describe radiation
interactions
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3.
Learning Objectives
List charged and uncharged particles
Write the equation that describes how
uncharged particles are attenuated
Describe/draw an image of how
uncharged particles penetrate into
matter
Calculate the:
Range of an alpha particle in air
Range of a beta particle in a known
material
Attenuation of a photon beam
Attenuation of a neutron beam
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4.
Basic Nuclear Particles
Atom: consists of protons,
neutrons & electrons
Proton, mass = 1.007277 amu
Neutron, mass = 1.008665 amu
Electron, mass = 0.000549 amu
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5.
Basic Nuclear Particles
Beta ( ), mass = 0.000549 amu
Positron ( +), mass = 0.000549 amu
Alpha (), mass = ~4 amu
Gamma ray, no mass
X ray, no mass
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6.
b er
num
ass N
M +
=Z
A
Z
Nuclear Terms
XN
At
nu om
m ic
be
r
ron
t
eu ber
N m
nu
Nucleons
Protons and neutrons
Nuclide
Species of atom defined by Z and A
1
H, 238U, 2H are all nuclides
Isotopes
Nuclides of same element (Z),
different number of neutrons (N)
1
H, 2H, 3H are isotopes of H
Isotones
Nuclides with same number of
neutrons
206
Pb and 204Hg
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7.
b er
num
ass N
M +
=Z
A
Z
Nuclear Terms,
continued
XN
At
nu om
m ic
be
r
ron
t
eu ber
N m
nu
Radionuclide
Radioactive nuclide
Radioisotope
Radioactive isotope
Radiation
Particles or waves with
sufficient energy to interact
with or cause ionization of the
atoms with which they interact
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8.
Classification of Nuclear Particles
ged
r
ha
C
art
P
s
cle
i
alpha (), + 2 charge
Proton, +1 charge
Electron, 1 charge
beta ( ), 1 charge
positron ( +), + 1 charge
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9.
Classification of Nuclear Particles
nc
U
ar
h
le s
tic
ar
dP
ge
Neutron
Gamma ray
X ray
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10.
Charged Particle Interactions
alpha ()
e
e
e
e
e
ionization
e
e
e
e
beta ( )
e
ionization
ee
e
e
positron ( )
Ionization
and
annihilation
radiation
e

+
ee

e
e
annihilation radiation
0.511 MeV
ee
e

e
e+
annihilation radiation
0.511 MeV
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11.
Uncharged Particle Interactions
photons
eeee
recoil nuclei
fast neutron
recoil nuclei
thermal neutron
diffusion
recoil nuclei
elastic scattering
of nuclei and
production of
recoil nuclei
photon
Absorption with
(n,) reaction
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12.
Important Radiation
Interactions in Matter
Production of Bremsstrahlung
Photon Interactions
Photoelectric Effect
Compton Effect
Pair Production
Positron Annihilation
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13.
Bremsstrahlung
Radiation
Electrons are
deflected and
accelerated in the
Coulomb field of
the nucleus.
e
Accelerated
electric
charges emit
electromagnetic
waves (Xrays)
e
e
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14.
Photon Interactions Photoelectric Effect
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15.
Photon Interactions Compton Effect
eJump to first page
16.
Photon Interactions –
Pair Production
e+
e
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17.
Photon Interactions –
Positron Annihilation
e+
e
e
e+
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18.
Important Equations
Alpha Particle Range
Beta Particle Range
Proton Range
Photon Absorption
Neutron Absorption
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19.
Alpha Particle Range
Rα = 0.318 E
3/ 2
Where:
Rα =
range in cm of air at 1
atm and 15oC
E =
energy in MeV
Note…this is an empirically derived
equation, the units don’t “work out”
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20.
pes
: Ty s
bar tion
ide ua
S eq Dimensionally correct
of
Internally consistent
May be physics based
May include empirically derived
Example:
Velocity (m/s) = distance (m) / time (t)
Units “work out”
Examples
Radiation attenuation equations
Radioactive decay
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21.
pes
: Ty s
bar tion
ide ua
S eq
Empirically derived
f
o
Experimental method of science
applied to the creation of equations.
Hypotheses generated to test theory
Data collected and analyzed.
Patterns extracted to describe
observed behavior
Units may not “work out”
Examples
Many “rules of thumb”
Range equations
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22.
Beta Particle Range
Rβ = 412 E
1.265 − 0.0954 ln E
For particles 0.01<E<2.5 MeV
Where
Rβ =
range expressed in mg/cm2
E =
maximum energy in MeV
Note…this is also an empirically
derived equation, the units don’t
“work out”
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23.
Proton Range
1.8
Rp
E
=
9 .3
Where
Rp =
E =
range expressed in
meters of air
energy in MeV (few MeV to 200
MeV)
Note…this is also an empirically
derived equation, the units don’t “work
out”
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24.
The “onesize fits all”
equation
N = N0e
−λ t
Activity decay equation
I = I0e
−µ x
Atom decay equation
A = A0 e
−λ t
Photon attenuation equation
And many more….
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25.
I=
Photon Absorption
− µx
I 0e
Where
I0 is the original exposure rate or beam
fluence or flux
I is the attenuated exopsure rate,
fluence or flux
µ is the linear absorption coefficeint
(cm1)
x is the thickness of the absorber
e is the base of the natural logarithm
(2.718..)
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26.
Neutron Absorption
I = I 0e
−σNx
Where
= I 0e
− Σx
I0 is the original neutron intensity
I is the attenuated neutron intensity
N is the number of atoms per cm3 in the
absorbing material
σ is the cross section of the abosrber
(capture coefficient (cm2)
x is the thickness of the absorber (cm)
e is the base of the natural logarithm
(2.718..)
Σ is the macroscopic cross section of the
absorber
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27.
Behavior of Exponential Functions
Linear plot
N0
Semilog plot
ln (N0)
N
ln N
t, x, or Z
t, x, or Z
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28.
The Chart of the Nuclides
Still available
See Jean Robinson, NE Office
A portable resource
Known elements
Stable and radioactive forms
Periodic table
Brief description of nuclear
properties
Conversion tables!
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34.
Summary
Basic constituents of the atom
Defined and give an examples of
nuclear terms
Described major radiation
interactions in matter
Listed equations to describe
radiation interactions
Layout of the Chart of the
Nuclides
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