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





3

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





4

Electromagnetic radiation

Gamma rays following radioactive decay

Annihilation radiation

Gamma rays follow N-reaction

Bremsstrahling

X-rays

Neutrons

Fast neutrons

Slow neutrons Thermal neutrons





5

LIGHT CHARGED PARTICLE SOURCES

Light

ChargedParticles

Beta

Decay

InternalConversion

Electrons

Auger

Electrons

Beta

Negative

Beta

Positive

Electron

capture





6

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





7

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





8

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





9

- 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





10

+ 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





11

Accompanying process of + decay

Electron capture Annihilation of positron and electron





12

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





14

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





15

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





16

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





17

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





18

HEAVY CHARGED PARTICLE

SOURCES

Heavy

Charged

Particles

ProtonsAlpha

Particles

Fission

Fragments





19

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





20

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





21

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





22

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





23

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




Dr. Muhammad Tufail(Izaz i Fazeelat)

24

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

1charged particulate radiation.ppt

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