Chapter 6: Collisions Flashcards
At what levels is electronic stopping power domiannt?
Dominant High Energies
What happens when charged particles and electrons in a solid medium interact?
Electrons are excited (energized) and removed from the nucleus leading to ionization of the medium along ion-track
What happens to the most energetic electrons in a charged particle - electron interaction?
Thermalized and re-captured by nuclei where ionization energy is degraded into heat.
At what energy levels are nuclear interactions predominant?
Low energies
What do nuclear interactions produce mainly?
Permanent atomic displacements within the solid (V&I)
What do atomic displacements cause?
Physical and Mechanical property changes.
In particle collision what happens when T > Ec
Electronic energy loss and no atomic displacements
In particle collision what happens when T < Ec
Mainley atomic displacements (nuclear stopping) which produces V&I
What is the displacement energy?
Energy needed to displace a lattice atom from its site in the crystal which leaves a vacant lattice site.
What is the average value for the displacement energy?
25 to 50 eV
What happens when E > Ec?
all energy loss is by ionization therefore no displacements
What happens when E < Ec?
all energy loss by displacement collisions with atoms
What is the average energy of fast reactor neutrons?
1 MeV
What is the average energy of a fusion neutron?
14 MeV
What effect does Vacancies and Interstitials causes in the mechanical properties of the material? What other factors enhance this effect?
Hardening, Embrittlement and Swelling. These effects are enhanced due to radiation-induced/enhanced diffusion, precipitation and segregation.
