Ionizing Radiation Flashcards
Radiological physics
The science of ionizing radiation and its interactions with matter, with special interests in the energy absorbed by matter
Radiation dosimetry
Has to do with the quantitative determination of energy
Energy needed to cause a valence electron to escape from an atom
4-25 eV
Types and sources of ionizing radiation
Gamma rays X Rays Fast electrons Heavy charged particles Neutrons
Gamma ray
Electromagnetic radiation emitted from a nucleus or an annihilation reaction between matter and antimatter (electron and positron)
Planks constant
h =6.626E-34J.s=4.136E-15keV.s
X-ray
Electromagnetic radiation emitted by electrons changing atomic levels (characteristic x Ray) or slowing down in a coulomb field (bremsstrahlung)
Energy range of x Ray
0.1-20 kv: low energy or soft x ray 20-120 kv: diagnostic x ray 120-300 kv: orthovoltage 200 kv - 1 Mv: intermediate 1 Mv and up: megavoltage
Fast electors and positrons
Photoelectrons Compton electrons Pair production electrons Megavoltage electrons β Rays Auger electrons IC electrons δ Rays
Photoelectrons
Electrons generated in a medium by photoelectric effect
Compton electrons
Electrons released in a medium by Compton effect
Pair production electrons
Electrons or positrons produced in a medium by pair production
Megavoltage electrons
Electrons produced by linear accelerator sixth kinetic energy 4 MeV to 30 MeV
β Rays
Electrons or positrons emitted from a nuclei
Auger electrons
Electrons from Auger effect
IC electrons
Electrons from internal conversion effect
δ Rays
Electrons resulted from a charged particle collision
Heavy charged particles
(Nuclei or ions) are usually obtained from acceleration by a Coulomb force field in a cyclotron or a linear accelerator
Types of heavy charged particles
Proton Deuteron Triton Helium Alpha Pions Neutrons Other
Types of ionizing radiation
Direct and indirect
Directly ionizing radiation
Fast charged particles which deliver their energy to matter directly through Coulomb force interactions along the particles track Single stage process The absorption of energy occurs by the ionization or excitation of atoms in the medium
Examples of directly ionizing radiation
Fast electrons and positrons, pions, heavy charged particles
Indirectly ionizing radiation
Uncharged particles - photons or neutrons Two step process: Transfer kinetic energy to charged particles in matter Resulting charged particles transfer energy to the medium through ionization and excitation of atoms
Examples of indirectly ionizing radiation
Neutrons, bremsstrahlung photons, annihilation photons, gamma ray, characteristic x ray
Stochastic quantity
Values occur randomly and cannot be predicted. A particular value is determined by a probability distribution. Defined for finite domains
Non stochastic quantity
Value can be predicted by calculation
Planar fluence
The number of particles crossing a fixed plane in either direction per unit area of the plane (summed by scalar addition)
Planar flux density
The number of particles per unit time passing through unit area of the plane on one side minus those going the other way.
Ionizing radiation
Subatomic particles or electromagnetic waves that are energetic enough to detach the electrons from atoms or molecules
Types of errors
Systematic Random
Systematic Error
comes from the measuring instrument affect accuracy of a measurement
Accuracy
Degree of closeness of a measurement of quantity to the quantities true value
Random errors
Caused by unknown and unpredictable changes of the experiment associated with precision
Precision
Degree to which repeated measurements under unchanged condition show the same results
Fluence
Fluence density (fluence rate)
Energy Fluence
Energy Fluence Density (Energy Fluence Rate)
Differential fluence density
Fluence Density Formula
Planar Fluence below the medium planar detector
Planar Fluence below the medium Sperical Detector
Gamma ray equation
gamma rays vs x-rays
gamma rays (nuclear process)
emitted from nuclear decay
annihilation of matter and antimatter
x-rays (atomic process)
when an electron transits from higher energy level to lower energy level
electron in the nuclear field loses kinetic energy
Radiant energy (R)
isotropic field planar fluence
