INFLUENCE OF Mg CONTENT ON TRAPPING EFFICIENCY IN Al–Mg SYSTEM BY POSITRON ANNIHILATION SPECTROSCOPY

2006 ◽  
Vol 13 (04) ◽  
pp. 485-488
Author(s):  
EMAD BADAWI ◽  
M. A. ABDEL-RAHMAN ◽  
M. O. ABDELHAMED
Keyword(s):  
Positron Annihilation ◽  
Cross Section ◽  
Positron Annihilation Spectroscopy ◽  
Trapping Efficiency ◽  
Doppler Broadening ◽  
Deformation Degree ◽  
S Parameter ◽  
Mean Lifetime ◽  
The Mean ◽  
Mg Content

PLT and Doppler broadening S-parameter were used for Al – Mg alloy, namely 5005, 5051, 5052 and 5083. The trapping efficiency was estimated for the pervious alloys as 2.42 × 109, 2.29 × 109, 2.24 × 109 and 2.27 × 109 s -1 cm 3, respectively and the trapping cross-section was estimated to be as 2.66 × 10-16, 2.14 × 10-16, 2.10 × 10-16 and 3.51 × 10-16 cm 2, respectively. It is clear that the mean lifetime and S-parameter have the same behavior as a function of deformation degree and saturated at the same value of thickness reduction.

Effect of Mg Contents on Trapping Efficiency in Al-Mg System Using PAS

2007 ◽  
Vol 265 ◽  
pp. 7-11
Author(s):  
N.A. Kamel
Keyword(s):  
Cross Sections ◽  
Mg Alloys ◽  
Trapping Efficiency ◽  
Thickness Reduction ◽  
Doppler Broadening ◽  
Degree Of Deformation ◽  
S Parameter ◽  
Mean Lifetime ◽  
The Mean ◽  
Al Mg Alloys

PLT and the Doppler broadening S-parameter were used to characterize the Al-Mg alloys, AA5005, AA5051, AA5052 and AA5083. The trapping efficiencies of these alloys were estimated to be 2.42 x 109, 2.29 x 109, 2.24 x 109 and 2.27 x 109 s-1 cm3, respectively, and the corresponding trapping cross-sections were estimated to be 2.66 x 10-16, 2.14 x 10-16, 2.10 x 10-16 and 3.51 x 10-16 cm2. It was found to be very clear that the mean lifetime and S-parameter exhibited the same behaviour as a function of the degree of deformation, and that they saturated at the same degree of thickness reduction.

POSITRON ANNIHILATION AND XRD FOR DETECTING Al ALLOYS (50XX)

2004 ◽  
Vol 11 (02) ◽  
pp. 167-171 ◽  
Author(s):  
EMAD BADAWI
Keyword(s):  
Positron Annihilation ◽  
Al Alloys ◽  
Preferred Orientation ◽  
Doppler Broadening ◽  
Degree Of Deformation ◽  
Mean Lifetime ◽  
Mg Content

The positron annihilation parameter (mean lifetime) increases with increasing Mg contents for annealed and quenched samples (50 XX ). Positron parameter τ, s (Doppler broadening) increase with increasing Q.T for the same (50 XX ). The preferred orientation is one of the most important parameters that can be observed by XRD for materials, for such measurements in our observation: the dependence of the preferred orientation on the Mg content, the dependence of the preferred orientation on the Q.T, and the dependence of the preferred orientation on the degree of deformation.

Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

2012 ◽  
Vol 331 ◽  
pp. 41-52 ◽  
Author(s):  
Andreas Wagner ◽  
Wolfgang Anwand ◽  
Maik Butterling ◽  
Thomas E. Cowan ◽  
Fine Fiedler ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Linear Accelerator ◽  
Electron Accelerator ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Electron Linear Accelerator ◽  
Positron Annihilation Lifetime ◽  
Electron Bremsstrahlung ◽  
New Type ◽  
Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

A theory of incoherent scattering of radio waves by a plasma

1960 ◽  
Vol 259 (1296) ◽  
pp. 79-99 ◽  
Keyword(s):  
Cross Section ◽  
Thermal Fluctuations ◽  
Incoherent Scattering ◽  
Doppler Broadening ◽  
Radio Waves ◽  
Central Frequency ◽  
Resonance Effects ◽  
Doppler Shifts ◽  
The Mean ◽  
Free Plasma

A theory is developed which describes the scattering of radio waves by the random thermal fluctuations of electron density in a collision-free plasma. The frequency spectrum, as well as the amplitude, of the scattered radiation is calculated. Particular attention is paid to the part of the spectrum which corresponds to small Doppler shifts, this being the region of greatest significance in connexion with the phenomenon of incoherent scattering from the ionosphere. The calculations are based on a generalized version of Nyquist’s noise theorem, and they lead to the following conclusions: (1) The mean scattering cross-section for the ionosphere is equal to that which would exist if each of the electrons scattered independently with a cross-section of one-half the classical Thomson cross-section. (2) The mean Doppler broadening of the scattered signal corresponds roughly to the speed of the ions rather than to that of the electrons. (3) The spectral shape of this signal is not Gaussian. There is a mild maximum in the spectrum away from the central frequency, as can be seen in figure 1. (4) Plasma resonance effects contribute only negligibly to the scattering for frequencies currently of interest.

The Evolution Behavior of Defects in the Nanofilms of W/Cu and W Probed by Doppler Broadening Positron Annihilation Spectroscopy

2017 ◽  
Vol 373 ◽  
pp. 104-107
Author(s):  
Ling Wang ◽  
Ai Hong Deng ◽  
Kang Wang ◽  
Yong Wang ◽  
Xiao Bo Lu ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Storage Time ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Radio Frequency Magnetron Sputtering ◽  
Helium Ions ◽  
Near Surface ◽  
Evolution Behavior

W/Cu multilayer nanofilms and pure W nanofilms were prepared in pure Ar and He/Ar mixing atmosphere by radio frequency magnetron sputtering method. The defect evolution of the samples was characterized by Doppler broadening positron annihilation spectroscopy (DB-PAS).The results show that plenty of defects can be produced by introducing helium (He) into W/Cu multilayer nanofilms. With the natural storage time increasing, the helium located in the near surface of W/Cu multilayer nanofilm would be released gradually and induce the coalescence of the helium related defects due to the diffusion of the helium and defects. In addition, the pure W nanofilms were irradiated by 30 keV helium ions and 40 keV hydrogen (H) ions in sequence at room temperature. From the DB-PAS analysis, it can be shown that a large number of vacancy-type defects are produced due to the He and/or H irradiation. H ions would be trapped by He related defects and produced He-H-V complexes.

DETECTING DEFECTS IN AIRCRAFT MATERIALS BY NUCLEAR TECHNIQUE (PAS)

2005 ◽  
Vol 19 (22) ◽  
pp. 3475-3482
Author(s):  
EMAD. A. BADAWI
Keyword(s):  
Aluminum Alloy ◽  
Dislocation Density ◽  
Material Science ◽  
Positron Annihilation Spectroscopy ◽  
Defect Concentration ◽  
Nuclear Technique ◽  
Nuclear Techniques ◽  
Mean Lifetime ◽  
The Mean ◽  
7075 Alloy

Positron annihilation spectroscopy (PAS) is one of the nuclear techniques used in material science. The present measurements are used to study the behavior of defect concentration in one of the most important materials — aluminum alloy — which is a 7075 alloy. It has been shown that positrons can become trapped in imperfect locations in solids and their mean lifetime can be influenced by changes in the concentration of such defects. No changes have been observed in the mean lifetime values after the saturation of defect concentration. The mean lifetime and trapping rates were studied for samples deformed up to 58.3%. The concentration of defect range varies (from 1015 to 1018 cm-3) at the thickness reduction, (from 2.3 to 58.3%). The range of the dislocation density varies (from 108 to 1011 cm/cm3).

POSITRON INTERACTION IN POLYMERS

2004 ◽  
Vol 19 (23) ◽  
pp. 3951-3959 ◽  
Author(s):  
CORINE BAS ◽  
N. DOMINIQUE ALBÉROLA ◽  
MARIE-FRANCE BARTHE ◽  
JÉRÉMIE De BAERDEMAEKER ◽  
CHARLES DAUWE
Keyword(s):  
Positron Annihilation ◽  
Chemical Structure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Hole Size ◽  
Doppler Broadening ◽  
Positron Source ◽  
Positron Annihilation Lifetime ◽  
Doppler Broadening Spectra ◽  
Variable Energy

A series of dense copolyimide membranes was characterized using positron annihilation spectroscopy. The positron annihilation lifetime spectroscopy performed on film with a classical positron source gives informations on the positronium fraction formed and also on the hole size within the film. The Doppler broadening spectra (DBS) of the gamma annihilation rays coupled with a variable energy positron beam allow the microstructural analyses as a function of the film depth. Experimental data were also linked to the chemical structure of the polyimides. It was found that the presence of the fluorine atoms strongly affects the positron annihilitation process and especially the DBS responses.

scholarly journals Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy

2008 ◽  
Vol 6 (4) ◽  
pp. 575-580 ◽  
Author(s):  
R. Bryaskova ◽  
R. Mateva ◽  
N. Djourelov ◽  
M. Krasteva
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Main Chain ◽  
Positron Annihilation Spectroscopy ◽  
Polyamide 6 ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Degree Of Crystallinity ◽  
Doppler Broadening ◽  
Annihilation Line ◽  
Positron Annihilation Lifetime

AbstractPositron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ3) and o-Ps intensity (I3) has been performed.

Effect of Irradiation Doses on AlCu6.5 Alloy Using Positron Annihilation Doppler Broadening Technique

2008 ◽  
Vol 278 ◽  
pp. 15-24
Author(s):  
M. Abdel-Rahman ◽  
Yahia A. Lotfy ◽  
M.A. Abdel-Rahman ◽  
Emad A. Badawi
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Dose Effect ◽  
Doppler Broadening ◽  
Γ Irradiation ◽  
Cu Alloy ◽  
Versatile Tool ◽  
Parameter Values ◽  
Line Shape Parameter

Positron Annihilation Spectroscopy (PAS) is a powerful and versatile tool for the study of the microscopic structure of materials. Doppler Broadening Positron Annihilation Technique (DBPAT) is the fastest technique used among positron annihilation techniques. The dose effect in Al-6.5at. % Cu alloy was investigated by means of DBPAT. An abrupt change in both the S and W line-shape parameter values occurred at 70 kGy of irradiation. The S- and W-Parameters of the trapped positrons at 70 kGy of γ−irradiation dose are about 48 % and 14 % respectively. The S- versus W-parameter reveals a linear relationship indicating the presence of only one type of defect. The S- and W-parameters have been used in the determination of the positron trapping rate and the grain size of the AlCu6.5 alloy.

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