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25 Cards in this Set
- Front
- Back
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Ionization |
Ionization is any process that results in the removal of a bound electron (negative charge) from an electrically neutral atom or molecule by adding enough energy to the electron to overcome it's binding energy |
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Excitation |
Electron excitation is any process that adds enough energy to an electron of an atom or molecule so that it occupies a higher energy state (smaller binding energy) then its lowest bound energy state (ground state) |
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Bremsstrahlung |
Bremsstrahlung is the radioactive energy loss of moving charged particles as they interact with the matter through which they are moving |
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Specific ionization |
(Average number of) ion pairs produced (by a charged particle) per unit distance traveled in an absorbing medium.
Abbreviation: S.I.
Units: Ion pairs/cm |
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L.E.T- linear energy transfer |
(average value of) energy locally deposited by a (charged particle) in an absorbing medium per unit distance (kev/cm) |
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Stopping power |
Stopping power of an absorber is its ability to remove energy from a beam of charge particles. Stopping power is measured as the average energy lost by charged particle per unit distance traveled
Abbreviation: S
Units: Kev/cm |
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Range |
RANGE (R)- Average distance traveled by radiation in an absorbing medium
Abbreviation: R
Units: cm |
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W-Value |
The average amount of energy needed to produce an ion pair in a given medium
Abbreviation- W
Units- eV/ion pairs |
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Identify the two major mechanisms of energy transfer for alpha radiation |
1- IONIZATION 2- EXCITATION |
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3 major mechanisms of energy transfer for beta particulate radiation |
1- Bremsstrahlung 2- ionization 3- excitation |
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The photoelectric effect |
The photo electric effect is an all at once energy loss. The Photon imparts all of its energy to an electron of an atom. The photon since it consisted only of energy in the first place simply vanishes. The photoelectric effect is only significant for initial photon energies that are less than 1 MeV. |
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Compton scattering |
In Compton scattering there is a partial energy loss for the incoming photon. The photon interacts with an orbital electron of some Atom and only part of the energy is transferred to the electron. Compton scattering is the dominant interaction for most materials for photon interactions between 200 KeV and 5 MeV |
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Pair production |
Pair production occurs when all the energy of the photon is converted to mass. This conversion of energy to mass only occurs in the presence of a strong electric field which can be viewed as a catalyst. Pair production is impossible unless the gamma rays are greater than 1.022 MeV of energy to make up the rest mass of the particles. |
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Neutron energies categories |
Thermal ~.025eV - .5eV
intermediate. .5eV - 100KeV
Fast. 100KeV - 20MeV
Relativistic >20MeV |
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Beta particles |
beta particles are high speed electrons or positrons, usually emitted by an atomic nucleus undergoing radioactive decay. A Beta particle is a free (unbound) electron with kinetic energy (e.g. Unbound electron) |
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Photoelectron |
Is a high velocity electron. Photoelectron is a directly ionizing particle and typically has sufficient energy to knock out the electrons from orbit of other atoms and it goes on its way to produce a secondary ion until all the energy is expended |
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Identify the three major mechanisms by which gamma photon radiation interacts with matter |
1 - the photoelectric affect
2 - Compton scattering
3 - pair production |
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3 possible results of neutron capture for slow neutrons. |
1: Radioactive capture with gamma emission
2: charged particle emission
3: fission |
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Elastic scattering |
The Neutron strikes a nucleus of approximately the same size and is deflected off at a lower energy. The nucleus recoils off with the energy lost by the neutron. |
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Inelastic scattering |
Neutron strikes a large nucleus. The neutron is absorbed and then emitted at a lower energy. The nucleus is left in an excited state and emits a gamma photon |
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Alpha shielding material |
Thin amounts of most any material (paper,unbroken dead cell layer of skin, a few cm of air) |
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Beta shielding material |
Low Z and low density material. (Rubber, aluminum, plastic) |
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Gamma shielding material |
High Z and high density material (lead, depleted uranium) |
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Neutron shielding material |
Hydrogenous material for moderation (oil, plastic, water) and capture material for absorption (boron,cadmium) |
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Indirectly ionizing radiation |
The types of radiation they have no charge (electromagnetic radiation and neutrons) have no: force field extending beyond their physical dimensions to interact with electrons. They must come sufficiently close to particles such as protons so that their physical dimensions contact and interact with these particles |
