Search results for "Positronium"
showing 3 items of 33 documents
The Effect of Impact Pressure on Positron Lifetime in Ultra High Molecular Weight Polyethylene (PE-UHMW)Chirulen®1120
2010
The paper presents the results of investigations of the effect of impact pressure (in the range of both elastic and plastic deformations) on the parameters of the positron lifetime spectra in PE-UMHW polymer known under the trade mark Chirulen1120. The changes in the long-living component of the positron lifetime spectrum, connected with the annihilation of o-Ps in the pick-off process, are analyzed in dependence on the impact energy. The impact duration in the Charpy’s tests depending on the impact energy was measured, too. The dependencies of the radius of the volume of empty spaces in which the positronium annihilates, on the impact pressure were determined applying the Eldrup-Tao model.
Positron Annihilation in Alkali Halides at Low Temperatures
1986
We report on low-temperature positron studies for pure, single crystals of the alkali halides KCl, NaCl and NaF. Strong temperature dependences are observed in the lifetime and angular correlation measurements in the temperature range 10–300 K. Delocalized para-positronium is observed at low temperatures in the three crystals. The broadening, with rising temperature, of the narrow peak in the angular correlation curve can be accounted for by the self-trapping model of positronium. The results are discussed in the light of this model, in terms of positronium localization at imperfections and in terms of positron interactions with imperfections created in the spur of the positron. The increas…
The influence of mechanical damaging on the lifetime of positrons In ultrahigh-molecular polyethylene
2013
We study the influence of damaging of ultrahigh-molecular polyethylene [(PE-UHMW) Chirulen®1120] applied, among other materials, in the production of hip endoprostheses on the spectra of positrons lifetime in this material. Polyethylene samples were damaged by the impacts, rolling friction, and collisions with metal balls in a planetary mill. The changes in the parameters of the spectra of positrons lifetime related to the annihilation of orthopositronium (o-Ps) were analyzed depending on the mechanical energy transferred to the sample. On the basis of the Eldrup–Tao model, the changes in the radii of voids in which positroniums are formed and annihilated and the changes in the degree of fi…