scholarly journals Source for In Situ Positron Annihilation Spectroscopy of Thermal—And Hydrogen-Induced Defects Based on the Cu-64 Isotope

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6693
Author(s):  
Iurii Bordulev ◽  
Roman Laptev ◽  
Denis Kabanov ◽  
Ivan Ushakov ◽  
Viktor Kudiiarov ◽  
...  

This work aims to investigate the 64Cu isotope applicability for positron annihilation experiments in in situ mode. We determined appropriate characteristics of this isotope for defect studies and implemented them under aggressive conditions (i.e., elevated temperature, hydrogen environment) in situ to determine the sensitivity of this approach to thermal vacancies and hydrogen-induced defects investigation. Titanium samples were used as test materials. The source was obtained by the activation of copper foil in the thermal neutron flux of a research nuclear reactor. Main spectrometric characteristics (e.g., the total number of counts, fraction of good signals, peak-to-noise ratio) of this source, as well as line-shaped parameters of the Doppler broadening spectrum (DBS), were studied experimentally. These characteristics for 64Cu (in contrast to positron sources with longer half-life) were shown to vary strongly with time, owing to the rapidly changing activity. These changes are predictable and should be considered in the analysis of experimental data to reveal information about the defect structure. The investigation of samples with a controlled density of defects revealed the suitability of 64Cu positron source with an activity of 2–40 MBq for defects studies by DBS. However, greater isotope activity could also be applied. The results of testing this source at high temperatures and in hydrogen atmosphere showed its suitability to thermal vacancies and hydrogen-induced defects studies in situ. The greatest changes in the defect structure of titanium alloy during high-temperature hydrogen saturation occurred at the cooling stage, when the formation of hydrides began, and were associated with an increase in the dislocation density.

1995 ◽  
Vol 73 (1-2) ◽  
pp. 11-17 ◽  
Author(s):  
D. W. Lawther ◽  
R. A. Dunlap

A Doppler-broadening positron-annihilation-spectroscopy experiment that utilizes an in situ 64Cu source for the study of Cu and Cu-containing materials is described. This technique is particularly useful for the investigation of defect structure at elevated temperatures, and the present instrumentation provides reliable results up to about 1000 °C. The method described is applicable to Cu-containing samples with as little as about 0.1 at.% Cu. Results from measurements on a single crystal of elemental Cu are compared with literature results obtained using other positron-annihilation methods and electrical-resistivity studies.


2010 ◽  
Vol 666 ◽  
pp. 99-102 ◽  
Author(s):  
Maria Fatima Ferreira Marques ◽  
A.M.G. Moreira Da Silva ◽  
P.M. Gordo ◽  
Z. Kajcsos

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.


2005 ◽  
Vol 34 (3) ◽  
pp. 181-186
Author(s):  
V. I. Grafutin ◽  
O. V. Ilyukhina ◽  
G. G. Myasishcheva ◽  
V. V. Kalugin ◽  
E. P. Prokopiev ◽  
...  

2020 ◽  
Vol 137 (2) ◽  
pp. 205-208 ◽  
Author(s):  
S.W.H. Eijt ◽  
T.W.H. de Krom ◽  
D. Chaykina ◽  
H. Schut ◽  
G. Colombi ◽  
...  

2019 ◽  
Vol 517 ◽  
pp. 148-151 ◽  
Author(s):  
O.V. Ogorodnikova ◽  
L. Yu Dubov ◽  
S.V. Stepanov ◽  
D. Terentyev ◽  
Yu.V. Funtikov ◽  
...  

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