INTERACTIONS OF IONIZING RADIATION WITH MATTERS DR. CHAU VAN TAO DEPARTMENT OF NUCLEAR PHYSICS NATURALSCIENCES UNIVERSITY
Dec 30, 2015
INTERACTIONS OF IONIZING RADIATION WITH MATTERS
DR. CHAU VAN TAODEPARTMENT OF NUCLEAR PHYSICS
NATURALSCIENCES UNIVERSITY
Questions
What is radiation?
What is ‘ionizing’ radiation?
How do we measure radiation?
Where does radiation come from?
What are the effects of radiation?
Is radiation good for anything?
nucleusnucleus
proton
neutron
electronelectron
Atomic Structure and Radioactive DecayAtomic Structure and Radioactive Decay
Atomic StructureAtomic Structure
RöntgenRöntgen
18951895
Discovery Discovery of X-rayof X-ray
Pierre & Marie Pierre & Marie CurieCurie 18981898 Discovery ofDiscovery of Ra, Ra, PoPo
Becquerel Becquerel
18961896
SpontaneouSpontaneous s radioactivitradioactivityy
Hahn Hahn
19381938
Discovery Discovery of fissionof fission
Discovery of Radiation Discovery of RadiationDiscovery of Radiation
Ernest Rutherford(1871-1935) Albert Einstein(1879- 1955)
Types of Radiation and Nuclear Energy
Atomic Structure and Radioactive DecayAtomic Structure and Radioactive Decay
Atoms and IsotopesAtoms and Isotopes
XN
A
Z
X: Chemical SymbolX: Chemical Symbol
AA: : Atomic mass numberAtomic mass number
ZZ: : Atomic numberAtomic number
N: Neutron numberN: Neutron number
or X-A
He4
2 He-4
A=Z+N4 2 2
electronelectron
Atomic Structure and Radioactive DecayAtomic Structure and Radioactive Decay
Co-60
Proton : 27Neutron: 33
Ni-60*
Proton : 28Neutron: 32
-decay and -decay and -ray emission-ray emission
Ni-60
Proton : 28Neutron: 32
electromagneticelectromagneticradiationradiation
More Radioactivity
+60Co Beta ray(electron)
++226Ra Alpha ray
(helium nucleus)
7BeGamma ray
+-electron
7Be 7Li +
11C 11B + +
60Co 60Ni + –
226Ra 222Rn +
+11C Positron
Antoine Henri Becquerel
(1852—1908)
Antoine Henri Becquerel
(1852—1908)
Discovered radioactivity of uranium
Discovered radioactivity of uranium
proton
neutron
Atomic Structure and Radioactive DecayAtomic Structure and Radioactive Decay
-decay-decay
U-238
Proton : 92Neutron: 146
Th-234
Proton : 90Neutron: 144
nucleusnucleus
-ray
Lead block
Radioactive substance
-ray
-ray
-ray
(+)
(-)
Electrically charged plates
Photographic plate
Types of RadiationTypes of RadiationTypes of RadiationTypes of Radiation
Types of RadiationTypes of Radiation
Types of radiation Charge
Mass
(amu)Remarks
-ray +2 4Very short range
Highly ionizing
-ray -1 0.0005 Short range
-ray 0 0 Long range
neutron 0 1 Long range
Types of RadiationTypes of Radiation
Half-life Time of RadionuclideHalf-life Time of Radionuclide
Characteristics of RadiationCharacteristics of Radiation
A = A0e-t
: Probability of disintegration per unit time
Half Life, T 1/2 = log2 /
Half-life Time of RadionuclideHalf-life Time of Radionuclide
Characteristics of RadiationCharacteristics of Radiation
Nuclide Half-life24Na 15.0 h
222Rn 3.8 d131I 8.0 d
60Co 5.3 y90Sr 28.8 y
137Cs 30 y226Ra 1600 y239Pu 24000 y238U 4.5x109 y
Characteristics of RadiationCharacteristics of Radiation
Penetrating DistancesPenetrating Distances
and X
neutron
Paper Plastic Lead ConcreteSkin Aluminum Iron Water
Electromagnetic Radiation
f = c/f = c/
Speed of lightBUT:
Radiation can also be interpreted as particles (photons) with energy E
E = hfE = hf
Planck’s constant
‘Ionizing’ Radiation
+
++
+
-
-
Radiation that is energetic enough to remove a tightly bound electron from a neutral atom
Radiation that is energetic enough to remove a tightly bound electron from a neutral atom
RadiationElectron
Ion
‘Ionizing’ Radiation
Different kinds of radiation produce different patterns of ionizationDifferent kinds of radiation produce different patterns of ionization
+++ + + +
+++ + + +
+++ + + +
+++ + + +
Electromagnetic Spectrum
IonizingNon ionizing
AA
Measuring Radiation (Ion Chamber)
Measuring Radiation (Geiger Counter)
Geiger–Müller Tube
Geiger–Müller Tube
Measuring Radiation (Scintillator)
1024…
4096… 410 = 1,048,576
ScintillatorScintillator Light guideLight guide
Photomultiplier tube
Photomultiplier tube
DynodesDynodes
Electrical pulse
Electrical pulse
1
4
16
64
256
PhotocathodePhotocathode
The Gamma Spectrometer
Lesson 1 - Inverse Square Law of Gamma Radiation
I0
x1
I1
I0
21
01 x
IkI
x2
I1I2
I0
2
1
x
mm mm
logk-2logx
oI/I
2o
x
IkI
oI/I
2o x
k
I
I xlog2klog]I/Ilog[ o
x x
Io
Lesson 2 –The Decrease Of Gamma Intensity
Interaction of Radiation with MatterInteraction of Radiation with Matter
Interaction ofInteraction of Electromagnetic RadiationElectromagnetic Radiation withwith Matter Matter
Photoelectric Effect
photoelectron
raye-
E: energy of the incident photonEs: energy of the scattered photonq : the scattering anglem: electron mass
Interaction of Radiation with MatterInteraction of Radiation with Matter
Interaction ofInteraction of Electromagnetic RadiationElectromagnetic Radiation withwith Matter Matter
Compton Scattering
ray
’ray
electron
e-
Pair Production
Interaction of Radiation with MatterInteraction of Radiation with Matter
E = 2mc2 + E+ + E-
m: electron rest massc: the speed of lightE+: kinetic energies of the positron E-: kinetic energy of the electron
Interaction ofInteraction of Electromagnetic RadiationElectromagnetic Radiation withwith Matter Matter
positron
electron
raye-
e+
Interaction of Radiation with MatterInteraction of Radiation with Matter
Photoelectric Effect
Pair Production
Compton Scattering
µ
xo e.II
Ix
xe
mm mm
-x
oI/I
xo e.II
oI/I
xo eI/I x]I/Iln[ o
x x
electronelectron
Co-60
Proton : 27Neutron: 33
Ni-60*
Proton : 28Neutron: 32
Lesson 3 - The Gamma Spectrum
Ni-60
Proton : 28Neutron: 32
electromagneticelectromagneticradiationradiation
Lesson 3 - The Gamma Spectrum
Cobalt Spectrum
THANK YOU FOR ATTENTION