1. ZCT 532/4 Radiation Physics
Lecturer: Eid M. E. Abdel_Munem
B.Sc. Mutah Univ. Jordan, M.Sc. & Ph.D. USM Malaysia
Language: English
Meet 27 times for lectures and tests
2 Tests
Assignments
Tests will contribute 30 %

2. Lecture schedule Wed. 9/7 11:00 am Fri. 11/7 3:00 pm
Midterm Break 16-24/8

3. Syllabus Introduction to radiation and nuclear physics Radioactivity.
Decay schemes and energy level diagrams
Naturally occurring isotopes.
Radiation sources including accelerators.

4. Interaction of radiation with matter.
Interaction of photons with matter. Photoelectric effect. Compton process. Coherent scattering. Pair production. Annihilation radiation. Attenuation coefficients

5. Interaction of electrons and heavy charged particles with matter
Interaction of electrons and heavy charged particles with matter. Absorption process. Scattering ionisation and excitation. Bethe’s equation. Bremsstrahlung. Range of beta particles. Back scatter and self-absorption.
Energy loss by collision. Range-Energy relation and Bragg Curve. Specific ionisation. Stopping power.

6. Detection of radiation.
Scintillation detectors.
Gas detectors
Semiconductor detectors.
Other detectors of radiation.

7. Neutron sources.
Interaction of neutrons with matter. Neutron capture. Elastic scattering. Energy transfer. Inelastic scattering. Dependence on E and Z.
Neutron activation.

8. Textbooks Knoll G.F. “Radiation Detection and Measurement” Wiley
Attix F.H. “Introduction to Radiological Physics and Radiation Dosimetry” Wiley
James Martin “Physics for Radiation Protection” Wiley
Abdul Ghaffar Ramli “Keradioaktifan: Asas dan Penggunaan” DBP

9. If the “Available” time overlaps with your classes, try to see me during any of the labs or in my room “304”.
You can me at: or preferably at:
In case of emergency only, you can call me at:

10. Introduction to Structure of matter and Nuclear transformation

11. Discovery of the electron
Joseph John Thomson 1897 B x E

12. Discovery of „X-Strahlen“
Röntgen 1895

13. Discovery of radioactivity
Henri Bequerel 1896

14. Discovery of the proton as a product of a nuclear reaction Ernest Rutherford 1919

15. Discovery of the neutron
James Chadwick 1932

16. Nuclear nomenclature
Embedded within the atom is a small but massive core of matter – the nucleus
Diameter of atom ~ m
Diameter of nucleus ~ m (i.e. ~ 10 fm)
Nucleus comprises of neutrons and protons (nucleons). {These particular constituents of the nucleus are more broadly categorized as hadrons, i.e. certain combinations of quarks, antiquarks and gluons, and in terms of their quark constituency they are of the sub-category baryons}.
The nuclei X are differentiated by use of the symbolic representation , Z being the number of protons in a particular nucleus (referred to as atomic number) and A being the number of nucleons in that nucleus (i.e the total number of protons and neutrons – referred to as the mass number). As such, there are A − Z neutrons in a nucleus.
e.g. 23Na has Z = 11 and (A − Z) = 12. The atomic weight of this element is close to 23 u (where 1 u is 1 atomic mass unit, sometimes also written as amu). The atomic weight takes account of the weight fraction of the various isotopes comprising an element.

17. The nucleus A the mass number (Nproton+ Nneutron)
Z the atomic number (Nproton )
isotope same Nproton, different Nneutron
isotone same Nneutron, different Nproton
isobar same (Nneutron+ Nproton), different Nproton
isomer  same Nproton, same Nneutron,
different nuclear energy state

18. Isotopes:
e.g.
Z 17 17
N 18 20
(Note that both isotopes are stable – those that are not are referred to as radionuclides.)
Isotones:
Z 1 2
N 1 1
Isobars:
3He 3H (tritium, an unstable istotope of hydrogen)

19. Charts of isotopes
Z=N
Isotone
Isotope
Isobar

20. The nuclear chart

22. Atomic mass 1 amu = mass of = 1.660510-27 kg
Close to actual mass of proton
1.672610-27 kg
Or the neutron
1.674910-27 kg

23. Energy Units 1 eV =1 V1.602 10-19 C =1.602 10-19 J
Einstein’s principle of equivalence of mass and energy

24. 1.2 Nuclear Mass
Mass of nucleus ~ mass of the atom (note that the electron mass
me = −31 kg and is almost negligible compared to the mass of a nucleon)
mp ~ 1836 me
mn ~ 1839 me
The mass of a nucleus (in g) is given by:
where is Avogadro’s number.

25. Nuclear Mass Consider a free, atomic electron:
me = 9.1x10-31 kg with equivalent energy = mec2 = 9.1x10-31 (3.0 x 108)2 joules
= 511 keV
This can be compared with the energy equivalent of a nucleon of ~ 931 MeV
[1 u = MeV].

26. Radioactive decay law
The radioactive decay law was first established experimentally near the beginning of the 20th century by Rutherford and Soddy and states that the activity of a radioactive sample decays exponentially in time. In terms of modern QM, this can be derived by considering the fact that a nuclear decay process is governed by a transition probability per unit time, , characteristic of the nuclear species.

27. Decay constant ()

28. Activity
Activity, or intensity of radioactive emission, is the number of atoms that undergo transformation to new atoms per unit time.

29. Activity
1 Ci =3.71010 disintegrations/sec
=3.71010 dps
=3.71010 Bq

30. The half-life (T1/2) & the mean life (T)

31. Radioactive equilibrium
Equilibrium is established in a parent/daughter mixture when the daughter’s half-life is shorter than that of the parent.

32. Radioactive equilibrium

33. Secular Equilibrium
A condition reached when the half-life of the parent is many many times greater than the half-life of the daughter, (T1  T2),
eg., times greater. To keep things in perspective, during 10 half-lives of the daughter, decay of the parent is negligible. Decay of the parent is represented by the flat line in the figure in the next slide.

34. Secular equilibrium T1>>T2 (1<<2) A2 = A1 activity
time
activity

35. Transient equilibrium
A condition reached when the half-life of the parent is greater than the half-life of the daughter, (T1  T2), eg., 10 times greater.

36. Transient equilibrium
T1>T2 (1<2)
Transient equilibrium
time
activity

37.  particle decay Q = the disintegration energy
= the difference in mass between the parent
nucleus and product nuclei
E   5  10 MeV (discrete energy)

38. ….theory of alpha decay
To come out of the nucleus the alpha particle must either surmount or tunnel through a Coulomb barrier.
Only possible, with appreciable probability if α-particle has energy of a few MeV.
Alpha particles have well defined mean range R in air, given by:
referred to as Geiger-Nuttall Law

40. ….theory of alpha decay
For α’s in the energy range from ~ 3 to 8 MeV, the range in air (in cm) is given by:
with E in MeV.
Hence
(with A, B, C, D as constants).

41. Fermi Theory of Beta Decay
Continuous nature of β-spectrum suggests that individual nucleons in decay do not always emit electrons (negatrons and positrons) of the same energy.
Leads to problem of conservation of energy.
A further problem is the conservation of angular momentum.

43. Pauli, in 1927, suggested the existence of a new particle, created and emitted during each β-decay process, with attributes as follows:

44. Electron (-) emission
An excessive number of neutrons or a high neutron-to-proton (n/p) ratio
anti-neutrino
Q = the difference in mass between and the
sum of the masses of and the particles
emitted.

45. Electron emission
A negatively charged electron is emitted by the nucleus, Z increases by one and N decreases by one and A remains fixed:
where mZ,A and mZ+1,A are the mass of the parent and product nucleus respectively and M signifies the respective atomic masses. The mass of the electron added to the atom is compensated by the mass of the electron emitted.

46. Positron(+) emission
A deficit of neutrons or a low n/p ratio
neutrino
Annihilation
0.511 MeV photon +
positron 
free electron

47. Positron emission The nucleus emits a positively charged positron:
In positron emission, the atom must emit one electron since its nucleus emits one positron and has one less positive charge. Therefore the initial atomic mass must exceed the final atomic mass by 2me = u

48. ….positron emission
Eg.
Therefore the lithium nuclide is lighter and hence stable to beta decay (the mass difference is u) so that the decay proceeds via electron capture.

49. The -ray spectrum
The average energy of the  particles is approximately Emax/3.

50. Electron capture
The unstable nuclei with neutron deficiency may increase their n/p ratio by EC.
An alternative process to the positron decay
K capture characteristic x-rays
(L or M capture) Auger electrons

51. Electron capture
A nucleus captures a negatively charged atomic electron:
eg.

52. Characteristic radiation
An empty hole in a shell is filled by electron from outer shell with an emission of characteristic radiation.
discrete energy
h=EK - EL
hole K L M

53. Auger Electrons
The absorption of characteristic X-rays by orbital electrons and reemission of the energy in the form of monoenergetic electrons
discrete energy
E=h-EM=EK – EL-EM K L M
hole

54. Internal conversion
Conversion electron from K shell
E = h-Eb K
Nuclear  ray h
Hole in K shell
The excess nuclear energy is passed on to one of the orbital electrons which is then ejected from the atom.
To create a vacancy in the involved shell, resulting in the production of characteristic photons or Auger electrons

55. Nuclear Reactions Of the form:
with a the accelerated particle, X the target nucleus and Y and b the reaction products.
An alternative notation is X (a , b) Y.

56. …..nuclear reactions In X (a , b) Y ,
if a is a gamma ray, then the reaction is called a nuclear photoeffect.
If b is a gamma ray then the reaction is called radiative capture.

57. Reaction classification
If the incident and outgoing particles are the same (ditto X and Y), then this is a scattering process.
In addition, if Y and b are in the ground state then it is an elastic scattering process.
In an inelastic scattering process (with Y or b or both in an excited state) then de-excitation is generally by gamma emission.

58. …reaction classification
Sometimes a and b are the same particle, accompanied by a third particle (i.e. three particles in the final state): this is referred to as a knockout reaction.
An alternative is the transfer reaction eg incoming deuteron, outgoing proton or neutron, resulting in addition of a nucleon to target X, forming Y.

59. Nuclear reactions (1) The , p reaction The , n reaction
Threshold energy
AX (, p) A+3Y
The , n reaction
Proton bombardment
Deuteron bombardment

60. Nuclear reactions (2) Neutron bombardment Photon disintegration
Neutron, no electric charge
effective in penetrating the nuclei and producing nuclear reactions
n,  reaction
Photon disintegration
Fission
Chain reaction
Fusion

61. Activation of nuclides
The yield of a nuclear reaction
The number of bombarding particles (eg n flux)
The number of target nuclei (eg Weight)
The probability of the occurrence (eg n cross-section)
Cross-section
1 barn = cm2 = m2
The growth of activity
Saturation activity

62. Reaction Cross-Section
A measure of the relative probability of a reaction occurring.
Imagine a detector placed to record particles b emitted in direction (, ) with respect to the beam direction.

64. ...reaction cross-section
Let Rb be the production rate of the outgoing
particles:
with dimensions of area per nucleus.
Consider for instance a nuclear radius
R = 6 fm, yielding geometrical area R2 ~ 100 fm2 ~ 1b

65. Angular dependence of cross-section
Typically the outgoing particle will not be emitted isotropically and as such angular distribution will depend on  and ,
, so that:
referred to as the differential cross-section.

66. Integrated cross-section
Hence:
is the total cross-section, integrated over all angles.

67. Thank you for your attention!