Transcript Document

Basic Nuclear Physics - 2
Excitation, Ionisation, X-ray production
and Auger electrons
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Day 1- Lecture 2
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Objective
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To discuss the excitation and ionisation
which are processes by which electrons are
removed from their stable location
•
To learn about accelerated charged particles,
x-rays, Bremsstrahlung, Characteristic Xrays and Auger electrons
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Contents
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Binding Energy
Excitation and Ionisation
Accelerated charged particles and x-rays
X- ray units
Bremsstrahlung
Characteristic Radiation
Auger electrons
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Electron Shells
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Electron Shells
K
L
M
N
O
2n2
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Shell
n
Maximum No.
of Electrons
K
1
2
L
2
8
M
3
18
N
4
32
O
5
50
P
6
72
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Binding Energy
Shell Hydrogen Tungsten
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K
-13.5
-69,500
L
-3.4
-11,280
M
-1.5
-2,810
N
-0.9
-588
O
-0.54
-73
(Binding Energy in eV)
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Binding Energy
Binding Energy (keV)
110
100
90
80
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
Atomic Number (Z)
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Excitation
atom
excited state
electron
orbitals
energy
energy
nucleus
ground state
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Excitation
higher energy level
excited
electron
energy
normal energy level
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Excitation
nucleus
energy
electron
excited state
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Excitation
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Ionisation
Ionisation of an outer
shell electron
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Ionisation
Ionisation of a Kshell electron
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Accelerated Particles
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Bremsstrahlung
T u n gste n
n uc le u s
W
X-ra y
e-
In one process radiation is emitted by the high-speed
electrons themselves as they are slowed or
even stopped in passing near the positively charged
nuclei of the anode material. This radiation is
often called Brehmsstrahlung [Ger.,=braking radiation].
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Bremsstrahlung
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X-Ray Unit
G LA SS
EN V EL OP E
EL EC TR O N
ST RE AM
FILA M E N T
CA TH O DE
AN OD E
TU NG ST E N
TA RG ET
U S E F U L X -R A Y S
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F O C U S IN G
C UP
W IN D O W
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Diagnostic Medical X-Ray Unit
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Characteristic Radiation
incident
electron
vacancy
created
electron
transition
x-ray
emitted
In a second process radiation is emitted by the
electrons of the anode atoms when incoming
electrons from the cathode knock electrons near the
nuclei out of orbit and they are replaced by other
electrons from outer orbits
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Characteristic Radiation
O p tic a l e n e rg y l e ve ls
O p tic a l
ra d ia tio n
L ra d ia tio n
0
u n e x c ite d
a to m
O
N
N
M ra d ia tio n
M
25 00
M
LL
K
w
W
L
1 1 ,0 0 0
L ra d ia tio n
O p t ic a l
o rb its
K ra d i a tio n
E n e rg y
( 6v)
n o t to s c a le
K ra d ia tio n
V a le n c e
e l e c tro n
K
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7 0 ,0 0 0
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Polyenergetic vs
Monoenergetic X-Rays
Polyenergetic
E1
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E2
E3
E4
E5
E6
E7
E8
E9
Energy
E10 E11 E12 E13 E14
Emax
Polyenergetic vs
Monoenergetic X-Rays
missing
due to
filtration
Polyenergetic
E1
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E2
E3
E4
E5
E6
E7
E8
E9
Energy
E10 E11 E12 E13 E14
Polyenergetic vs
Monoenergetic X-Rays
Monoenergetic
Polyenergetic
E1
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E2
E3
E4
E5
E6
Eeff
E7
E8
E9
Energy
E10 E11 E12 E13 E14
Characteristic Radiation
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Characteristic Radiation
O p tic a l e n e rg y l e ve ls
O p tic a l
ra d ia tio n
L ra d ia tio n
0
u n e x c ite d
a to m
O
N
N
M ra d ia tio n
M
25 00
M
LL
K
w
W
L
1 1 ,0 0 0
L ra d ia tio n
O p t ic a l
o rb its
K ra d i a tio n
E n e rg y
( 6v)
n o t to s c a le
K ra d ia tio n
V a le n c e
e l e c tro n
K
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7 0 ,0 0 0
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Auger Electrons
 Auger electrons are a special case of Internal
Conversion.
 During the Internal Conversion Process, a gamma
photon from the nucleus interacts with and transfers
all of its energy to a tightly bound (K-shell) orbital
electron.
 The electron is ejected from the atom with
considerable energy, equal to that of the initial
gamma photon minus the binding energy.
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Auger Electrons
characteristic x-ray
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Auger electron
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Where to Get More Information
 Cember, H., Johnson, T. E, Introduction to Health Physics,
4th Edition, McGraw-Hill, New York (2009)
 International Atomic Energy Agency, Postgraduate
Educational Course in Radiation Protection and the Safety of
Radiation Sources (PGEC), Training Course Series 18,
IAEA, Vienna (2002)
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