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7/28/2019 1Charged Particulate Radiation.ppt
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PNRA Course onRadiation Safety
Dr. Muhammad Tufail(Izaz-i-Fazeelat)
2
SOURCES/ORIGIN OF RADIATION
Radiation
Types
ChargedParticulate
Radiation
Uncharged
Radiation
Heavy
Charged
Particles
Light
Charged
Particles
Electro-
magnetic
Radiation
Neutrons
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Light charged particles
Beta decay
Beta negative
Beta positive
Electron capture (Competitive process)
Internal conversion electrons
Auger electrons
Heavy charged particles (m 1 amu)
Proton Alpha particle
Fission fragments
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Electromagnetic radiation
Gamma rays following radioactive decay
Annihilation radiation
Gamma rays follow N-reaction
Bremsstrahling
X-rays
Neutrons
Fast neutrons
Slow neutrons Thermal neutrons
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LIGHT CHARGED PARTICLE SOURCES
Light
ChargedParticles
Beta
Decay
InternalConversion
Electrons
Auger
Electrons
Beta
Negative
Beta
Positive
Electron
capture
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LIGHT CHARGED PARTICLES
Beta () Decay
It is a process of emission of a charged
particle (-ve or +ve) from the nucleus of an
atom whose mass is equal to that of an
electron. The emission of -vely charged electron
(negatron) from the nucleus is decay
The emission of +vely charged electron
(positron) from the nucleus is called +
decay
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The decay process is given as follows:
and decay process is given as follows:
where X and Y are the initial and final nuclear species, and are neutrino and antineutrino,and Q represents the amount of energy releasedin the decay process, called the Q-value of thereaction
Q=(M X +M e -M Y ) amu
The Q-value is shared between particleand or -
1
A A
Z Z X Y Q
1
A A
Z Z X Y Q
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particle Energy
Continuous spectrum
E max = Q value
Negligible energy is taken by the recoil
nucleus
Accompanying process of beta decay is the
emission of Bremsstrahlung
max3
1 E E
X e
e M M
Q E /1
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- Decay
A neutron in the nucleus is converted into a
proton
Example
Qe pn
0
0
0
1
1
1
1
0 )(
0
1
3
2
3
1 He H
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+ Decay
A proton in the nucleus is converted into a
neutron Example Qen p
0
0
0
1
1
0
1
1 )(
0
1
11
5
11
6 BC
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Accompanying process of + decay
Electron capture Annihilation of positron and electron
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Electron capture
An atom shell electron is capture by the nucleus
ExampleQne p
0
0
1
0
0
1
1
1
Lie Be7
3
0
1
7
4
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Internal Conversion Electrons
Conversion ProcessThe process in which the energy of an excited
nucleus state is transferred to an atomic
electron ejecting it from
the atom
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IC Electron Energy
Energy of internal conversion electron
where Ee- is kinetic energy of electron, EB is binding
energy of the electron in its atomic shell
Energy spectrum
Electron is emitted with
discrete energy as is
shown in figure
* B Ee E E
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IC Electron conti.
Conversion coefficient
where Ne is number of conversion electrons and N
is number of competing gamma photonsAssociated processes
X-rays
From vacancy filling
Bremsstralung
From electron slowing
Ne
N
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Auger Electrons
The process in which
the excitation energyof an atom is
transferred to atomic
shell electrons
This process is in
completion with
emission of X-rays
The process is favored
in low Z-materials
Electron energy is
discrete in nature
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HEAVY CHARGED PARTICLE
SOURCES
Heavy
Charged
Particles
ProtonsAlpha
Particles
Fission
Fragments
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Protons
There is no radionuclide that decay by
proton emission Protons are produced as a result of nuclear
reactions
There is not any laboratory proton source
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Alpha () Decay
An alpha particle is a highly energetic
helium nucleus that is emitted from the
nucleus of the radioactive isotope when the
neutron-to-proton ratio is to low
It is positively charged, massive particle,consisting of two protons and two neutrons
Almost all the naturally occurring alpha
emitters are heavy elements with Z 83
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Alpha () Decay Process
The decay process is written schematically
as follows:
where X and Y are initial and final nuclear species
The principal features of alpha decay arecan be learnt from the following example
4 4
2 2
A A
Z Z X Y Q
226 226 4
88 86 2 Ra Rn Q
22686 0.186r Rn r E MeV
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Alpha particle energy
Energy of alpha
particle Mono energetic
Discrete energy
spectrum
Energy relation with
half life
Alpha particles with
the highest
energies are those
with shortest half
life
1 x
Q
E m M
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Spontaneous Fission
The fission process is the only
spontaneous source of energetic heavycharged particles with mass greater than
that of the alpha particle.
The most widely used laboratory source is252Cf
Effective half life is 2.65 y.
QY X y
65.2
Q s sn Z Y X y
'' 85
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SF Conti.
Each fission gives rise
to two fissionfragments, which by
conservation of
momentum are emitted
in opposite direction. Mass and energy
distributions are shown
by figures