Important of Health care Physics and Radiation Physics students. It gives gross knowledge about interaction of radiation.

1. INTERACTIONOFRADIATION
WITHMATTER
Presented by- Satish Kumar
MSc. Nuclear Medicine Technology
SGPGIMS, Lucknow

2. RADIATION
• It is a form of energy in motion through space. It is emitted by
one object and absorb or scattered by another.
• On the basis of ionization it is of two types that is
1.Ionizing radiation
2.Non ionizing radiations .

3. IONISIZING RADIATION AND
NON IONISING RADIATION.
• Ionizing can ionize the matter because its quanyum
energy exceeds the ionization potential of atoms.
• It is also of two types that is - Directly ionizing radiations
and Indirectly ionizing radiations example of ionizing
radiations are X-rays, Y-rays, neutrons, electrons, protons
and heavier particles.
• Non ionizing radiations it cannot ionize matter because it's
potential energy per Quantum is below than ionization
potential of atom example of such radiations are
ultraviolet radiations visible light infrared photos
microwaves and radio waves.

4. • Further- we divide radiation in two types
1.Particulate radiations (Non-Penetrating Radiation)
2. Electromagnetic radiations (Penetrating Radiation)

5. Particulate and Electromagnetic Radiation
• Particulate radiation is a type of radiation having mass
and charge except neutrons which are neutral particles
the velocity of their motion depends upon the kinetic
energy the particulate radiations originate from radioactive
decay, cosmic race, nuclear reaction and show fourth.
• Electromagnetic radiation are of form of energy in motion
that doesn't have mass and charge and propogate as
either wave or discrete packet of energy called the
photons or quanta this radiation travel with the velocity of
light examples of electromagnetic radiations are radio
waves visible waves heat waves gamma radiations and
so forth.

6. Interaction with matter
• The mechanism of interactions with matter is of two types
• From charged particles and second from gamma
radiations
• From charged particles- Crenkov radiations, specific
ionization, LET, Range, Bremsstrahlung, Annihilation.
• From Gama radiations- photoelectric effect and
Crompton scattering, pair production, Raleigh scattering ,
photo disintegration occurs.

7. Interaction of Gamma rays with matter
• Interaction of gamma radiations with matter occurs when
penetrating gamma rays pass through matter, they lose
energy by interaction with the orbital electron or the
nucleus of the absorber atom.

8. Photo Electric Effect
• Generally it occurs with the inner shell electron. Incident
gamma rays transfer all its energy to an orbital elements of the
absorber atom when by the electron called the photo electron
is ejected with kinetic energy equal to energy of gamma ridge
minus binding energy.
• Generally it occurs in material having higher atomic mass and
number it is proportional to Z3/E3.
• The photo electron effect occurs primarily in the low energy
range and decreases sharply with increasing photon energy.
• It is then followed by emission of a characteristic x ray or auger
electron analogous to the situation in internal conversion or
electron capture decay. The photoelectric effect occurs mostly
in k shell 80% only 20% contributes of any higher cells.

10. Compton scattering
• In compton scattering gamma rays photons transfer only
a part of its energy to an electron in the outer shell of the
absorber atom and the electron is ejected.
• Energy decrease and wavelength increases deflected
from its original direction called Crompton scattering.
• The scattered photon of low energy may then undergo
further photoelectric or Crompton interaction and the
Compton electron may cause ionization or excitation.
• Compton scattering is almost independent of the atomic
number Z of the absorber. It contributes primarily in the
energy range of 0.1 - 10 mev depending on the type of
absorber.

12. Pair production
• Pair production When the gamma ray photon is greater
than 1.02 Mev the photon can interact with the nucleus of
the absorber atom during its passes through it and a
positive electron and a negative electron are produced at
expense of the photon.
• The energy is excess of 1.02 mev appears as the kinetic
energy of the two particles. This process is called pair
production.
•
• It varies almost linearly with Z2 of the absorber and
increase slowly with the energy of the photon.

14. RALEIGH SCATTERING
• It is also known as coherent or clasical scattering. In
Raleigh scattering a gamma rays can interact with the
atom as a whole atom instead of individual orbital
electrons , whereby the photons energy is spent for the
atom to oscillation in phase.
• The atom then releases the energy in the form of the
gamma ray with the same energy as the initial gamma ray
which is emitted at the slightly different angle then the
emitted gamma ray. It occurs with low energy photons
<40 kev.

15. PHOTO DISINTEGRATION
• PHOTO DISINTEGRATION is also known as photo
nuclear reaction.
• When the gamma ray photon is very high (>10) mev the
photon may interact with the nucleus of the absorber atom
and transfer sufficient energy to the nucleus such that one
or more nucleus may be emitted. This process is called
photodisintegration and produces new nuclides.

16. ATTENUATION OF GAMMA RADIATIONS
LINEARAND MASDATTENUATION COEFFICIENT
• Gamma rays and x rays photons are either attenuated or
transmitted as they travel through an absorber.
Attenuation results from the absorption by the
photoelectric effect, Crompton scattering and pair
production of high energy.
• It is an important factor in radiations protection.
• If a photon beam of initial intensity I passes through an
absorber of thickness x then the transmitted beam is
given by

18. HALF VALUE LAYER & TENTH VALUE LAYER
• Half value layer of an absorbing material for gamma d and
x radiations is important in the design of ceiling for
radiation protection does it reduce the intensity to 1/2 it
depends on the energy of the radiation and the atomic
number of the absorber. It is greater for high energy
photons and is smaller for high atomic number materials.
• TENTH VALUE LAYER
It is the thickness of and absorber died reduces the initial
beam by a factor of 10. It is given by ..

19. INTERACTION OF CHARGED
PARTICLES WITH MATTER
• Interactions of charged particles with matter such as alpha
particles protons deuterons and beta particles interact with the
absorber atom while passing through it.
• Interaction occurs primary with the orbital electron rarely with
the nucleus both are ionization and excitation may occur.
• In ionization the energy transferred may be sufficient to
overcome the binding energy of orbital electrons ultimately
ejecting from the atom by the incident charged particles are
called primary electrons.
• The higher energy secondary electron from the secondary
ionization are referred to as delta rays. Increasing occurs in this
process continues on till incident particles and electron come to
rest.

20. CRENKOV RADIATION
• Then charged particles travel through or medium at a
speed greater than the speed of light they polarized
molecules of the medium which then turn back rapidly to
their ground state by emitting radiation in the process that
is blue is in color it's called Cerenkov radiations it creates
a phonic shock wave...

21. SPECIFIC IONIZATION
• Specific ionization (SI) is the total number of ion pairs
produced per unit length of the path of the incident
radiation. The SI values of α-particles are slightly greater
than those of protons and deuterons, which in turn are
larger than those of electrons.
• Specific ionization increase with decreasing energy of the
charged particles and create a peak on end that is called
bragg ionization

22. LINEAR ENERGY TRANSFER
• The linear energy transfer (LET) is the amount of energy
deposited per unit length of the path by the radiation.
From the preceding, it is clear that
• LET= SI X W
• It is expressed in units of keV/μm and is very useful in
concepts of radiation protection.

23. RANGE
• Range of a charged particle in abure is the straight line
distance traversed by the particle in the direction of
particle it depends on mass charge kinetic energy density.
Heavy ions have short range. It occurs of two types
straight and zigzag..

24. BREMSSTRAHLUNG
• When energetic charged particles particularly electron,
pass through matter and come close to the nucleus of the
atom they lose energy as a result of deceleration in the
coulomb field of atomic nuclei. The loss in energy appears
as a X ray that is called Bremsstrahlung.
• It's production increase with the kinetic energy of the
particle and atomic number Z of the absorber atom.
• It in inversely proportional to the mass of the charged
particles and therefore is insignificant for heavy particles,
alpha particles and proton because the probability of
penetrating close to the nuclei is inversely low due to their
heavy masses.

26. ANNIHILATION
• When energetic beta particles pass through an absorber
they lose energy via interaction with orbital electron of the
atom of the absorber. When the beta particles comes to
close rest after losing all energy it combines with an
orbital electron of the absorber atom and produces two
511 kev annihilation radiations that are emitted in opposite
direction.
• It is used in PET instrument in Nuclear medicine

28. INTERACTION OF NEUTRONS WITH
MATTER
• Because neutrons are neutral particles, their interactions
in the absorber differ from those of the charged particles.
They interact primarily with the nucleus of the absorber
atom and very little with the orbital electrons.
• The neutrons can interact with the atomic nuclei in three
ways:
• 1.Elastic scattering
2.Inelastic scattering,
3.Neutron capture.

29. THANK YOU