Atoms are the fundamental units of matter. Composed of subatomic particles: protons, neutrons, and electrons. Unique identity determined by the number of protons (atomic number).

1. Atomic structure as applied to
generation of X-rays
Presenter: Dr. Dheeraj Kumar
MRIT, Ph.D. (Radiology and Imaging)
Assistant Professor
Medical Radiology and Imaging Technology
School of Health Sciences, CSJM University, Kanpur

2. An Atom
• Atoms are the fundamental units of
matter.
• Composed of subatomic particles:
protons, neutrons, and electrons.
• Unique identity determined by the
number of protons (atomic number).

3. Subatomic Particles
Protons:
• Positively charged particles found in the nucleus.
• Identify the element and determine the atomic number.
Neutrons:
• Neutral particles also located in the nucleus.
• Contribute to the mass of the atom.
Electrons:
• Negatively charged particles orbiting the nucleus.
• Determine the atom's size and participate in chemical reactions.

4. Electron Shells and Energy Levels
• Electrons organized into energy
levels or shells.
• Closer shells have lower energy
levels.
• Electrons in outer shells have
higher energy levels.

5. Atomic Number and Mass Number
• Atomic Number:
• Unique to each element.
• Equal to the number of protons.
• Mass Number:
• Sum of protons and neutrons in
the nucleus.
• Determines the mass of the atom.

6. The Nucleus
Title: The Core of Matter
• Central Role of the Nucleus:
• Nucleus at the center of the atom.
• Contains protons and neutrons.
• Dictates the element's properties

7. Protons and Neutrons
• Protons:
• Positively charged particles.
• Determine the atom's
identity.
• Neutrons:
• Neutral particles.
• Contribute to the mass.

8. Strong Nuclear Force
• Force binding protons and
neutrons together.
• Overcomes electromagnetic
repulsion between protons.
• Maintains stability within the
nucleus.

9. Electron Cloud
Electrons in Motion
• Electrons Orbiting the Nucleus:
• Electrons move in orbits around the
nucleus.
• Described by electron cloud or
probability density.
• Locations of electrons uncertain due to
quantum mechanics.

10. Quantum Mechanics and Uncertainty
Principle
• Quantum mechanics governs the
behavior of subatomic particles.
• Uncertainty principle: It's impossible
to simultaneously know the exact
position and momentum of a particle.
• Electron cloud provides a statistical
likelihood of electron location.

11. Electron Configuration and Energy Levels
• Electrons arranged in shells.
• Electrons in the outermost
shell determine chemical
properties.
• Movement between energy
levels involves absorption or
emission of energy.

12. Fundamental Forces
Forces Shaping the Atomic World
Overview of Four Fundamental
Forces:
• Gravity, electromagnetic, strong
nuclear, and weak nuclear
forces.
• Focus on electromagnetic force.
• Governs interactions between
charged particles.

13. Electromagnetic Force
• Attractive for opposite charges,
repulsive for like charges.
• Holds electrons in orbit around
the nucleus.
• Key in understanding atomic
interactions and X-ray
generation.

14. X-rays - An Overview
• Definition and Properties of X-rays:
• X-rays are high-energy electromagnetic waves.
• Invisible to the human eye.
• Penetrating ability through matter.
• Discovered in 1895 by Wilhelm Roentgen.
• Accidental discovery while experimenting with
cathode rays.
• Paved the way for medical imaging and various
applications.

15. Applications of X-rays
• Medicine:
• Diagnostic radiography, CT scans, fluoroscopy.
• Industry:
• Non-destructive testing, material analysis.
• Research:
• Crystallography, diffraction studies.

16. X-ray Production
Behind the Scenes of X-ray
Generation
• Two Primary Methods:
Bremsstrahlung and
Characteristic X-rays:
• Bremsstrahlung: Slowing down of
high-speed electrons.
• Characteristic X-rays: Inner-shell
electron transitions.

17. Explanation of Bremsstrahlung Radiation
• Interaction between high-speed electrons and target material.
• Energy loss results in X-ray emission.
• Dependent on electron energy and target material.
• Bremsstrahlung radiation is produced when high-energy electrons bombard a target, especially targets that have a
high proton number (Z). When bombarding electrons penetrate into the target, some electrons travel close to the
nucleus due to the attraction of its positive charge and are subsequently influenced by its electric field. The course
of these electrons would be deflected, and a portion or all of their kinetic energy would be lost. The principle of the
conservation of energy states that in producing the X-ray photon, the electron has lost some of its kinetic energy
(KE): final KE of electron = initial KE of electron - energy of X-ray photon. The ‘lost’ energy is emitted as X-ray
photons, specifically bremsstrahlung radiation (bremsstrahlung is German for ‘braking radiation’). Bremsstrahlung
can have any energy ranging from zero to the maximum KE of the bombarding electrons (i.e., 0 to Emax),
depending on how much the electrons are influenced by the electric field, therefore forming a continuous spectrum.
The intensity of bremsstrahlung radiation is proportional to the square of the atomic number of the target (Z), the
number of unit charges of the bombarding particle (z) and inversely with the mass of the bombarding particle (m):
Z² z / m123 [fm]

19. Bremsstrahlung Radiation
Interaction between High-Speed Electrons and Target Material:
• High-speed electrons directed at the target.
• Electrons experience deceleration or braking.
• Energy loss converted into X-ray photons.
Energy Loss and X-ray Emission:
• As electrons slow down, they release energy.
• This energy is emitted as X-ray photons.
• The energy of emitted X-rays is variable.
Factors Affecting the Energy of Emitted X-rays:
• Electron energy: Higher energy results in higher-energy X-rays.
• Atomic number of the target material: Affects the braking effect.

20. Explanation of Characteristic X-rays
• Inner-shell electron ejection.
• Transition of outer-shell electrons to fill the vacancy.
• Emission of characteristic X-rays with specific energies.
• Characteristic radiation is a type of energy emission relevant for X-ray production. It is represented by a line
spectrum and is emitted when a fast-moving electron collides with a K-shell electron, the electron in the K-
shell is ejected (provided the energy of the incident electron is greater than the binding energy of K-shell
electron) leaving behind a ‘hole’. An outer shell electron fills this hole (from the L-shell, M-shell, etc. ) with an
emission of a single x-ray photon, sometimes called a characteristic photon, with an energy level equivalent to
the energy level difference between the outer and inner shell electron involved in the transition. When an
electron falls (cascades) from the L-shell to the K-shell, the x-ray emitted is called a K-alpha x-ray. Similarly,
when an electron falls from the M-shell to the K-shell, the x-ray emitted is called a K-beta x-ray 1.

22. Characteristic X-rays
Signature X-rays from Electron Transitions
• Inner-Shell Electron Ejection:
• High-energy photons eject inner-shell electrons.
• Creates vacancies in inner electron shells.
• Transition of Outer-Shell Electrons:
• Outer-shell electrons transition to fill vacancies.
• Energy released during transitions.
• Emission of Characteristic X-rays:
• Unique X-rays emitted with characteristic energies.
• Depend on the specific element and electron transitions.

23. X-ray Tubes
• Title: Engine of X-ray Production
• Description of X-ray Tubes:
• Essential devices for X-ray generation.
• Consist of cathode and anode components.
• Controlled environments for efficient X-ray production.
• Cathode and Anode Components:
• Cathode:
• Emits electrons through thermionic emission.
• Focuses and directs electrons towards the anode.
• Anode:
• Target material where X-rays are generated.
• Experiences the impact of high-speed electrons.
• Generation of X-rays within the X-ray Tube:
• High-speed electrons strike the anode.
• Bremsstrahlung and characteristic X-rays are produced.
• X-rays exit the tube for clinical or industrial use.

24. Atomic Structure in X-ray Generation
The Role of Atomic Structure:
• Atomic structure determines the
behavior of electrons.
• Electron interactions within the
target atom to X-ray production.
• The connection between electron
energy levels and X-ray energy.

25. Relation Between Electron Energy Levels
and X-ray Energy
• Electrons at higher energy
levels release more energy
upon deceleration.
• This energy is manifested as
higher-energy X-rays.
• Understanding electron
transitions helps tailor X-ray
production.

26. How Different Target Materials Affect X-
ray Production
• The atomic number of the target
material influences X-ray
production.
• Higher atomic numbers lead to
greater energy loss and higher-
energy X-rays.
• Tailoring target materials is crucial
for specific applications.

27. X-ray Spectrum
Definition of X-ray Spectrum:
• X-ray spectrum encompasses all
X-ray energies produced.
• Continuous and characteristic X-
ray spectra.
Continuous Spectrum:
• Created by Bremsstrahlung
radiation.
• Displays a range of energies.
Characteristic Spectrum:
• Displays specific energy peaks.
• Unique to the target material.

28. Influence of Tube Voltage and Current on
X-ray Spectrum
• Tube voltage affects the
maximum energy of X-rays.
• Tube current influences the
number of X-rays produced.
• Adjusting these parameters
shapes the X-ray spectrum.

29. References
1.Serway, R. A., Jewett, J. W., & Wilson, L. (2016). Physics for Scientists and
Engineers with Modern Physics. Cengage Learning. (For foundational
concepts in atomic structure and electromagnetic forces)
2.Bushberg, J. T., Seibert, J. A., Leidholdt, E. M. Jr., & Boone, J. M. (2018).
The Essential Physics of Medical Imaging. Lippincott Williams & Wilkins.
(For principles of X-ray production and applications in medical imaging)