scholarly journals A new approach to near-surface positron annihilation analysis of ion irradiated ferritic alloys

2021 ◽  
Author(s):  
Vladimir Krsjak ◽  
Petr Hruška ◽  
Jarmila Degmova ◽  
Stanislav Sojak ◽  
Pavol Noga ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Ion Beam ◽  
Positron Beam ◽  
Ion Beam Irradiation ◽  
Near Surface ◽  
Slow Positron ◽  
New Approach ◽  
Ferritic Alloys ◽  
Positron Annihilation Lifetime ◽  
Variable Energy

The present work provides an innovative approach to the near-surface slow-positron-beam (SPB) study of structural materials exposed to ion-beam irradiation. This approach enables the use of variable-energy positron annihilation lifetime...

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.

Positron spectroscopy of bulk and near-surface defects in semiconductors

1989 ◽  
Vol 67 (8) ◽  
pp. 813-817
Author(s):  
P. Hautojārvi
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Surface Defects ◽  
Positron Beam ◽  
Near Surface ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Positron Lifetime Spectroscopy ◽  
Defects In Semiconductors ◽  
Ion Implanted

The use of positron annihilation to study defects in semiconductors is discussed. Positron-lifetime spectroscopy reveals As vacancies in as-grown GaAs and gives information on ionization levels. The vacancy profiles in ion-implanted Si are investigated by slow positron beam.

Temperature Dependence of Radiation Damage in ODS Steel Studied by Triple Beam Irradiation and Positron Annihilation Techniques

2017 ◽  
Vol 373 ◽  
pp. 91-95 ◽  
Author(s):  
Da Qing Yuan ◽  
Qiao Li Zhang ◽  
Ping Fan ◽  
Xian Ping Wang ◽  
Bin Long ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Ion Beam ◽  
Positron Beam ◽  
Doppler Broadening ◽  
Beam Irradiation ◽  
Single Beam ◽  
Positron Annihilation Lifetime ◽  
Ods Steel ◽  
S Parameter

The oxide dispersed strengthened (ODS) ferritic-martensitic steel was irradiated by 100MeV iron ion whose energy was degraded by using a Ta foil of 4 μm thick, 100 keV Hydrogen and 200 keV Helium at 480, 515, 550 and 580 °C. The irradiation fluences were 1×1016, 1.1×1015 and 6.8×1013/cm2, respectively for Fe, H and He. The techniques of positron annihilation lifetime and Doppler broadening of slow positron beam were utilized to examine the produced radiation damage. At 550 °C the maximal positron annihilation lifetime and S parameter of Doppler broadening were observed, implyin g tha t 550 °C is the pea k temperature of swelling. The S parameter and annihilation lifetime of the sample irradiated at 515 °C by the single Fe ion beam were smaller compared to the triple beam irradiation at the same temperature, implying that the triple beam irradiation caused more severe damage than the single beam irradiation.

Variable Energy Positron Annihilation Spectroscopy of Perovskite Oxides

2012 ◽  
Vol 331 ◽  
pp. 201-233 ◽  
Author(s):  
David J. Keeble
Keyword(s):  
Positron Annihilation ◽  
Oxygen Deficiency ◽  
Single Layer ◽  
Positron Annihilation Spectroscopy ◽  
Perovskite Oxide ◽  
Near Surface ◽  
Vacancy Defects ◽  
Positron Annihilation Lifetime ◽  
Primary Focus ◽  
Variable Energy

The application of variable energy positron annihilation spectroscopy (VE-PAS) methods to the study of perovskite oxide, ABO3, material thin films and near-surface regions is reviewed. The primary focus is on ferroic perovskite titanate oxide materials SrTiO3and Pb (ZrxTi1-x)O3, but studies of BaTiO3, LaxSr1-xCoO3, La0.67Sr0.33MnO3and YBa2CuO7-δare also included. Characterization of single layer and multilayer structures is discussed. The methods, in particular positron annihilation lifetime spectroscopy, allow the identification of cation vacancy defects at both the A-and B-sites with parts per million sensitivity. Varying oxygen deficiency is often observed to result in marked changes in PAS spectra; these effects are reviewed and discussed.

Slow Positron Beam Probe for the ZnO/Silicone under Proton Irradiation

2008 ◽  
Vol 607 ◽  
pp. 108-110
Author(s):  
Ying Ping Hao ◽  
Hui Min Weng ◽  
Chun Dong Li ◽  
Wei Feng Guo ◽  
Jian Dang Liu ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Crosslink Density ◽  
Proton Irradiation ◽  
Diffusion Length ◽  
Effective Diffusion ◽  
Positron Beam ◽  
Coating System ◽  
Slow Positron ◽  
Silicone Coating ◽  
Variable Energy

The degradation of ZnO/Silicone coating system under 90keV proton irradiation varying from 5×1014cm-2 to 1×1016cm-2, was studied by slow positron annihilation spectrum. Effective diffusion length calculated by Variable energy positron fit (VEPFIT) shows a dramatically break in a dose of 1×1015cm-2. It is ascribed to the increase of crosslink density and decrease of free volume and hole during the proton irradiation. Furthermore, positron has shown a satisfying sensitivity in detecting the nano-scale defect on ZnO/Silicone system.

scholarly journals Microscopy studies on magnetron sputtered thin films with preferred orientation for positron moderation

2019 ◽  
Vol 1 (1) ◽  
pp. 62-63
Keyword(s):  
Thin Films ◽  
Positron Annihilation ◽  
Branching Ratio ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Structure Characterization ◽  
Near Surface ◽  
Positron Annihilation Lifetime ◽  
Pass Through ◽  
Intrinsic Characteristic

Doppler-broadening Spectroscopy (DBS) and positron annihilation lifetime spectroscopy (PALS) are two positron annihilation spectroscopy techniques used for identifying near surface vacancies and lattice dislocations. Positrons manifest a broad energy distribution of about several MeV and in order to generate a low-energy positron beam, the positrons need to pass through a material called “moderator” so that a narrow positron kinetic energy bandwidth can be obtained, without losing too much intensity. The moderator must possess certain properties, among which a large negative positron work function and a large branching ratio to free positrons. The first can be assessed to an intrinsic characteristic of the material, that is usually correlated to the material bandgap, and in order to attain the second, a defect free, epitaxial thin film should be obtained. Due to its 3.4 eV bandgap, GaN represents a very promising candidate for positron moderation and field assisted moderation, that might manage longer average positron diffusion lengths. The aim of the present study is to obtain semi-insulating GaN thin films by magnetron sputtering GaN on different substrates (ZnO, TiO2, Al2O3) with fewer impurities incorporated, which should hold promises of increasing the positron diffusion length in the material. Preliminary depositions made in this study are to be discussed, highlighting both their advantages and limitations derived from their structure characterization.

scholarly journals PLEPS: Pulsed low energy positron system

2015 ◽  
Vol 1 ◽  
Author(s):  
Werner Egger
Keyword(s):  
Positron Annihilation ◽  
Depth Profiling ◽  
Positron Beam ◽  
Low Energy ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Variable Energy

PLEPS, operated by the Universität der Bundeswehr München, located at NEPOMUC, is a unique tool for depth profiling of defects with positron annihilation lifetime spectroscopy using a pulsed positron beam of variable energy.

scholarly journals On the Limitations of Positron Annihilation Spectroscopy in the Investigation of Ion-Implanted FeCr Samples

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1689
Author(s):  
Vladimir Slugen ◽  
Jarmila Degmova ◽  
Stanislav Sojak ◽  
Martin Petriska ◽  
Pavol Noga ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Positron Annihilation ◽  
Neutron Irradiation ◽  
Surface Region ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Radiation Embrittlement ◽  
Nuclear Facilities ◽  
Near Surface ◽  
Slow Positron

New materials for advanced fission/fusion nuclear facilities must inevitably demonstrate resistance to radiation embrittlement. Thermal and radiation ageing accompanied by stress corrosion cracking are dominant effects that limit the operational condition and safe lifetime of the newest nuclear facilities. To study these phenomena and improve the current understanding of various aspects of radiation embrittlement, ion bombardment experiments are widely used as a surrogate for neutron irradiation. While avoiding the induced activity, typical for neutron-irradiated samples, is a clear benefit of the ion implantation, the shallow near-surface region of the modified materials may be a complication to the post-irradiation examination (PIE). However, microstructural defects induced by ion implantation can be effectively investigated using various spectroscopic techniques, including slow-positron beam spectroscopy. This method, typically represented by techniques of positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy, enables a unique depth-profile characterisation of the near-surface region affected by ion bombardment or corrosion degradation. One of the best slow-positron beam facilities is available at the pulsed low-energy positron system (PLEPS), operated at FRM-II reactor in Munich (Germany). Bulk studies (such as high energy ion implantation or neutron irradiation experiments) can be, on the other hand, effectively performed using radioisotope positron sources. In this paper, we outline some basics of the two approaches and provide some recommendations to improve the validity of the positron annihilation spectroscopy (PAS) data obtained on ion-irradiated samples using a conventional 22Na positron source.

scholarly journals Development of a Slow Positron Beam System for in-situ Lifetime Measurements During Ion Beam Irradiation

2012 ◽  
Vol 35 ◽  
pp. 111-116 ◽  
Author(s):  
A. Kinomura ◽  
R. Suzuki ◽  
T. Ohdaira ◽  
N. Oshima ◽  
B.E. O’Rourke ◽  
...  
Keyword(s):  
Ion Beam ◽  
Positron Beam ◽  
Beam Irradiation ◽  
Ion Beam Irradiation ◽  
Lifetime Measurements ◽  
Slow Positron ◽  
Beam System
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