Interaction of nuclear radiation with matter

Its about nuclear radiation

1. Unit4: Interaction of Nuclear Radiation with matter: JAYASHRI KORI

2. CONTENT Gamma Ray Interaction with Matter Photoelectric Effect Compton Scattering Pair Production Energy Loss Due to Ionization (Bethe-Bloch Formula) Energy Loss of Electrons Introduction to Cerenkov Radiation

3. Gamma Ray Interaction with Matter Introduction Gamma rays, as high-energy electromagnetic radiation, interact with matter in several distinct ways. Understanding these interactions is critical for fields such as medical imaging, radiation therapy, and nuclear physics. Mechanisms of Interaction Photoelectric Effect : Gamma photon ejects an electron from an atom. Compton Scattering : Gamma photon scatters off a free or loosely bound electron. Pair Production : Gamma photon creates an electron-positron pair when interacting with a nucleus. Importance These interactions are foundational for technologies that rely on detecting or using gamma rays.

4. Photoelectric Effect Definition The photoelectric effect occurs when a gamma photon is absorbed by an atom, resulting in the ejection of an electron. Principles The photon's energy is transferred to an electron, overcoming the electron's binding energy and providing it with kinetic energy. The ejected electron's kinetic energy is given by Ek= hν−EbE_k = h\nu - E_bEk ​= hν −Eb​, where EbE_bEb ​ is the electron's binding energy .

5. Photoelectric Effect Energy Dependence This effect is most significant at low gamma ray energies (up to a few hundred keV). The probability of occurrence is proportional to Z5/E3Z^5/E^3Z5/E3, where ZZZ is the atomic number and EEE is the photon energy. Applications Enhances contrast in diagnostic radiography. Essential in X-ray and gamma-ray detectors. .

6. Compton Scattering Definition Compton scattering is the inelastic scattering of a gamma photon by an electron. Principles The gamma photon collides with an electron, transferring part of its energy to the electron and scattering at a reduced energy and changed direction. The energy of the scattered photon can be calculated using .

7. Compton Scattering Energy Dependence Predominant at intermediate gamma ray energies (hundreds of keV to a few MeV). The interaction probability is proportional to the atomic number ZZZ. Applications Useful in gamma spectroscopy for energy and angle measurements. Important for radiation shielding design. .

8. Pair Production Definition Pair production occurs when a gamma photon converts into an electron-positron pair upon interaction with the nucleus of an atom. Principles Requires photon energy greater than 2mec22m_ec^22me​c2 (1.022 MeV). The excess energy of the photon above this threshold converts to the kinetic energy of the electron and positron. Energy Dependence Dominant at high gamma ray energies (above 1.022 MeV). The interaction probability increases with photon energy and atomic number Z. .

9. Pair Production Applications Used in high-energy particle detectors. Relevant in medical physics for radiation therapy. .

10. Energy Loss Due to Ionization (Bethe-Bloch Formula) Introduction Charged particles lose energy mainly through ionization and excitation of atoms in the medium they pass through. Bethe-Bloch Formula Describes the mean energy loss per unit distance: Variables include Z (atomic number), A(atomic mass), z(charge of particle), β ( velocity/c), γ ( Lorentz factor), and I (mean excitation potential). .

11. Energy Loss Due to Ionization (Bethe-Bloch Formula) Energy Dependence Applies primarily to heavy charged particles such as protons and alpha particles. Applications Critical for designing particle detectors and planning radiation therapy dosages. .

12. Energy Loss of Electrons Mechanisms Ionization and Excitation : Primary modes of energy loss for electrons. Bremsstrahlung : Significant at higher energies, especially in materials with high atomic numbers (Z). Bethe-Bloch for Electrons Similar to the formula for heavy charged particles but includes considerations for radiative losses at high energies. Radiative Loss Radiative loss increases with energy and atomic number, proportional to E⋅Z2E \ cdot Z^2E⋅Z2. Applications Electron microscopy for imaging at microscopic scales. Radiation protection by designing effective shielding for electron beams. .

13. Introduction to Cerenkov Radiation Definition Cerenkov radiation occurs when a charged particle moves through a dielectric medium faster than the speed of light in that medium. Principles Speed Threshold : The particle's speed must exceed c/ nc / nc /n, where nnn is the medium's refractive index. Cerenkov Angle : The angle of emitted light is given by cos⁡θc = cnv \cos \ theta_c = \frac{c}{ nv } cosθc ​= nvc ​. Characteristics Continuous emission spectrum, with intensity peaking at shorter wavelengths, resulting in a characteristic blue glow. .

14. Introduction to Cerenkov Radiation Applications Used in Cerenkov counters for particle detection. Cerenkov luminescence imaging in medical diagnostics. Detecting high-energy cosmic particles in astrophysics. .