Evidence for shallow positron traps in a neutron-irradiated Al single crystal as studied with variable-energy positrons
A monoenergetic ( +- 1 eV), variable energy (0.5 to 4 keV) beam of positrons has been used to study the dependence on temperature (40 to 350 K) of positron diffusion out of a neutron-irradiated single crystal of Al. The results are interpreted in the context of a one-dimensional diffusion model which encompasses annihilations as well as trapping at voids and other microstructural defects in the bulk material by way of a removal rate kappa/sub eff/ of positrons from freely diffusing states. kappa/sub eff/ is found to have a slightly positive dependence on temperature above 125 K, as would be expected from previous measurements of the position trapping rate into large voids. The data suggest a strongly negative dependence on temperature below 125 K for kappa/sub eff/, indicating the presence of some additional phenomenon which we attribute to positron localization in shallow, presumably radiation-induced, traps in the crystal. The results of our analyses provide support for conclusions reached previously for neutron-irradiated Mo. During preliminary annealing treatments of the samples we found, by Auger-electrons spectroscopy, that Si produced by neutron-induced transmutation migrated to the crystal surface. It is conjectured that redistribution of Si within the sample is responsible for a recovery stage previously observed in neutron-irradiated Al between 400 and 470 K.
- Research Organization:
- Brookhaven National Laboratory, Upton, New York 11973
- OSTI ID:
- 5595071
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 25:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM
PHYSICAL RADIATION EFFECTS
TRAPS
POSITRONS
ANNIHILATION
DIFFUSION
ANNEALING
LOW TEMPERATURE
MEDIUM TEMPERATURE
MONOCRYSTALS
NEUTRONS
POSITRON BEAMS
TEMPERATURE DEPENDENCE
TRAPPING
VERY LOW TEMPERATURE
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYONS
BASIC INTERACTIONS
BEAMS
CRYSTALS
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRONS
HEAT TREATMENTS
INTERACTIONS
LEPTON BEAMS
LEPTONS
METALS
NUCLEONS
PARTICLE BEAMS
RADIATION EFFECTS
360106* - Metals & Alloys- Radiation Effects