[Triumf-seminars] TRIUMF Seminar today at 15:00

[postmaster@admin.triumf.ca]

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Date/Time: Tue 2005-03-08 at 15:00

Location:  Auditorium          

Speaker:   Sharon May-Tal Beck (Nuclear Research Center-Negev, Israel)

Title:     Probing point defects in materials using Positron Annihilation Spectroscopy

Abstract: Measurements of positron annihilation processes in matter enable studies of electronic structures in materials and radiation damage in its initial stages. Since an annihilation process evolves a positron and an electron, the emerging gamma particles carry information about the momentum of the participating electron and about the density of the electrons in the vicinity of the positron before it is annihilated. Positrons from a radioactive source penetrate into the bulk material and annihilate either in the bulk or in point defects that trap them. Mean positron lifetimes in the material vary with defect size and content. Thus, positron lifetimes are used as a probe to identify and characterize vacant defects, such as vacancies, vacancy clusters, voids and bubbles.

In the talk I will describe the different measuring methods in positron annihilation spectroscopy, with a special emphasis on lifetime measurements. Prelimenary results from measurements of positron lifetimes (PL) in irradiated Sapphire will be discussed. To demonstrate the sensitivity of this measuring method I will show also prelimenary results of PL measurements in Perovskite samples (SrRuO3 and CaMnO3).

Stimulants available 15 minutes before the talk.

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