scholarly journals Positron annihilation spectroscopy study of radiation-induced defects in W and Fe irradiated with neutrons with different spectra

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
O. V. Ogorodnikova ◽  
M. Majerle ◽  
J. Čížek ◽  
S. Simakov ◽  
V. V. Gann ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Radiation Effects ◽  
Defect Formation ◽  
Wide Spectrum ◽  
High Energy ◽  
Primary Radiation ◽  
Vacancy Clusters ◽  
Mean Size ◽  
Radiation Induced ◽  
Fission Neutrons

Abstract The paper presents new knowledge on primary defect formation in tungsten (W) and iron (Fe) irradiated by fission and high-energy neutrons at near-room temperature. Using a well-established method of positron-annihilation lifetime-spectroscopy (PALS), it was found that irradiation of W in the fission reactor and by high-energy neutrons from the p(35 MeV)-Be generator leads to the formation of small radiation-induced vacancy clusters with comparable mean size. In the case of Fe, smaller mean size of primary radiation-induced vacancy clusters was measured after irradiation with fission neutrons compared to irradiation with high-energy neutrons from the p(35 MeV)-Be generator. It was found that one of the reasons of the formation of the larger size of the defects with lower density in Fe is lower flux in the case of irradiation with high-energy neutrons from the p(35 MeV)-Be source. The second reason is enhanced defect agglomeration and recombination within the energetic displacement cascade at high energy primary knock-on-atoms (PKAs). This is consistent with the concept of the athermal recombination corrected (arc-dpa) model, although the measured dpa cross-section of both fission neutrons and wide-spectrum high-energy neutrons in W is between the conventional Norgett–Robinson–Torrens (NRT-dpa) and arc-dpa predictions. This means that the physics of the primary radiation effects in materials is still not fully known and requires further study through a combination of modeling and experimental efforts. The present data serve as a basis for the development of an improved concept of the displacement process.

RADIATION EFFECTS ON OPTICAL CHARACTERISTICS OF PbWO4

2008 ◽  
Vol 22 (21) ◽  
pp. 3695-3707 ◽  
Author(s):  
V. YEVSEYEV
Keyword(s):  
Optical Properties ◽  
Radiation Effects ◽  
Large Scale ◽  
Essential Role ◽  
Proton Irradiation ◽  
Defect Formation ◽  
High Energy ◽  
Radiation Defects ◽  
Lead Tungstate ◽  
High Energy Particles

The results of a study on the effect of γ- Co 60, fast (1 MeV) reactor neutron and 1 GeV proton irradiation on optical properties of lead tungstate ( PbWO 4) are presented. The peculiarities of optical absorption in PbWO 4 under these three types of irradiation are revealed. It is shown that in the case of irradiation of PbWO 4 with high energy particles 1 GeV protons, an essential role is played by large-scale radiation defects — disordered regions — and, related to it, fluctuating electrostatic potential. It is established that the efficiency of defect formation increases at the transition from gamma to neutron and further to proton irradiation.

High energy oxygen irradiation-induced defects in Fe-doped semi-insulating indium phosphide by positron annihilation technique

2017 ◽  
Vol 31 (04) ◽  
pp. 1750019
Author(s):  
S. Pan ◽  
A. Mandal ◽  
Md. A. Sohel ◽  
A. K. Saha ◽  
D. Das ◽  
...  
Keyword(s):  
Indium Phosphide ◽  
Positron Annihilation ◽  
Room Temperature ◽  
High Energy ◽  
Average Lifetime ◽  
Defect States ◽  
Positron Trapping ◽  
Radiation Induced ◽  
Induced Defects ◽  
Irradiation Induced Defects

Positron annihilation technique is applied to study the recovery of radiation-induced defects in 140 MeV oxygen (O[Formula: see text]) irradiated Fe-doped semi-insulating indium phosphide during annealing over a temperature region of 25[Formula: see text]C–650[Formula: see text]C. Lifetime spectra of the irradiated sample are fitted with three lifetime components. Trapping model analysis is used to characterize defect states corresponding to the de-convoluted lifetime values. After irradiation, the observed average lifetime of positron [Formula: see text] ps at room temperature is higher than the bulk lifetime by 21 ps which reveals the presence of radiation-induced defects in the material. A decrease in [Formula: see text] occurs during room temperature 25[Formula: see text]C to 200[Formula: see text]C indicating the dissociation of higher order defects, might be due to positron trapping in acceptor-type of defects ([Formula: see text]). A reverse annealing stage is found at temperature range of 250[Formula: see text]C–425[Formula: see text]C for [Formula: see text]-parameter probably due to the migration of vacancies and the formation of vacancy clusters. Increase in [Formula: see text]-parameter from 325[Formula: see text]C to 425[Formula: see text]C indicates the change in the nature of predominant positron trapping sites. Beyond 425[Formula: see text]C, [Formula: see text], [Formula: see text]-parameter and [Formula: see text]-parameter starts decreasing and around 650[Formula: see text]C, [Formula: see text] and [Formula: see text]-parameter approached almost the bulk value showing the annealing out of radiation-induced defects.

Radiation-Induced Defects in Si after High Dose Proton Irradiation

2017 ◽  
Vol 373 ◽  
pp. 209-212 ◽  
Author(s):  
Yurii V. Funtikov ◽  
Leonid Yu. Dubov ◽  
Yurii V. Shtotsky ◽  
Sergey V. Stepanov
Keyword(s):  
Bragg Peak ◽  
Proton Irradiation ◽  
Defect Formation ◽  
High Energy ◽  
High Dose ◽  
Number Density ◽  
High Energy Proton ◽  
Energy Proton ◽  
Radiation Induced ◽  
Induced Defects

Experiments on investigation of the radiation defects produced as a result of high energy proton irradiation of single crystal Si wafers are carried out. Parameters of the proton irradiation facility are presented. It is shown that the most efficient radiation defect formation correlates with the position of the Bragg peak of ionization losses. LT spectra were measured just after irradiation and then after keeping Si samples during 3 months of at room T. We did not observe any variation of the number density of the defects, except for the 7th wafer, where most part of protons was stopped. An efficient annealing of the vacancy-type defects starts at temperatures slightly lower than 100 °C (during 10 min). Annealing at about 700 °C leads to recovering of the monoexponrntial shape of the LT spectra.

Investigation of Dual-Beam-Implanted Oxide-Dispersed-Strengthened FeCrAl Alloy by Positron Annihilation Spectroscopy

2012 ◽  
Vol 331 ◽  
pp. 149-163 ◽  
Author(s):  
Reinhard Kögler ◽  
Wolfgang Anwand ◽  
Asta Richter ◽  
Maik Butterling ◽  
A. Mücklich ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Defect Formation ◽  
Positron Annihilation Spectroscopy ◽  
Vacancy Clusters ◽  
Open Volume ◽  
Dual Beam ◽  
Hardness Increase ◽  
Ods Alloy ◽  
Nuclear Applications

Oxide-dispersion-strengthened (ODS) FeCrAl steel is a class with promising materials to be applied for future nuclear applications. However, radiation damage, especially the formation of vacancy clusters or gas-filled bubbles, may result in hardness increase and the loss of ductility. Positron annihilation spectroscopy (PAS) is demonstrated to be a very useful and non-destructive analysis method to detect and to determine open volume defects of sub-nm size in ODS alloy. Synchronized dual beam implantation of Fe and He ions is performed to simulate the radiation damage caused by (n, α) reactions and to avoid induced activation. For room temperature implantation, i.e. without significant point defect recombination, the differences in the defect formation are shown by comparison between irradiation of ODS alloy and pure Fe bulk. The open volume defects created in ODS alloy are vacancy clusters closely connected with dispersed Y oxide nanoparticles. Their profiles are in reasonable qualitative agreement with the hardness profiles, indicating a relationship between sub-nm vacancy clusters or He bubbles and the hardness of the material. In heat-treated ODS alloy, containing larger vacancy clusters, the radiation induced hardness increase is more distinctive than for as-received ODS alloy. For irradiation at a moderately enhanced temperature of 300°C open volume defects are drastically reduced. The few remaining defects are vacancy clusters of the same type as in as-received ODS alloy. Close to the surface the open volume defects completely disappear. These results are in agreement with the hardness measurements showing little hardness increase in this case. The suitability of ODS-based materials for nuclear applications was verified.

Radiation-Induced Defect Formation in Ternary Ge-As-S Vitreous Semiconductors

2004 ◽  
Vol 230-232 ◽  
pp. 67-80 ◽  
Author(s):  
R.Ya. Golovchak ◽  
Oleg I. Shpotyuk
Keyword(s):  
Optical Properties ◽  
Positron Annihilation ◽  
Chemical Bond ◽  
Defect Formation ◽  
Topological Defect ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Mathematical Statistics ◽  
Positron Annihilation Lifetime ◽  
Radiation Induced ◽  
Using Data

A mechanism of g-induced (Co60 g-quanta of 1.25 MeV mean energy) changes in optical properties of ternary As-Ge-S chalcogenide vitreous semiconductors is analysed. It is connected with chemical bond re-switching accompanied by coordination topological defect formation. The origin of these defects for As-Ge-S system is discussed using data of positron annihilation lifetime spectroscopy, IR Fourier reflection measurements and mathematical statistics.

scholarly journals High Energies and Radiation Effects

2021 ◽  
pp. 135-149
Author(s):  
Donald V. Reames
Keyword(s):  
Radiation Dose ◽  
Radiation Effects ◽  
Radial Distance ◽  
High Energy ◽  
Upper Atmosphere ◽  
Energy Spectra ◽  
The Sun ◽  
Deep Space ◽  
Strong Function ◽  
Radiation Induced

AbstractIn this chapter we characterize the high-energy spectra of protons that can penetrate shielding and determine the radiation dose to humans and equipment in space. High-energy spectral breaks or “knees”, seen in all large SEP events, determine the contribution of highly penetrating protons. The streaming limit, discussed earlier, places an upper bound on particle fluences early in events and the radial variation of intensities is important for near-solar and deep-space missions. The streaming limit is a strong function of radial distance from the Sun. We also consider requirements for a radiation storm shelter for deep space, a mission to Mars, suitability of exoplanets for life, and radiation-induced chemistry of the upper atmosphere of Earth.

Radiation Effects in Rare-Earth Permanent Magnets

1987 ◽  
Vol 96 ◽  
Author(s):  
J. R. Cost ◽  
R. D. Brown ◽  
A. L. Giorgi ◽  
J. T. Stanley
Keyword(s):  
Neutron Irradiation ◽  
Radiation Effects ◽  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Open Circuit ◽  
Fast Neutrons ◽  
Rapid Loss ◽  
Before And After ◽  
Radiation Induced ◽  
Fission Neutrons

ABSTRACTNd-Fe-B and Sm-Co permanent magnets have been irradiated with fission neutrons and gamma rays. Irradiated samples were periodically removed for room temperature measurements of the open-circuit remanence. Hysteresis loops were measured before and after irradiation. For neutron irradiation, two Nd-Fe-B magnets showed a rapid loss of remanence, while a third magnet from another manufacturer decayed more slowly, suggesting that the radiation hardness of Nd-Fe-B magnets may depend on microstructural details. Irradiation in the Omega West Reactor at Los Alamos with fast neutrons caused the fast-decay samples to have an Wtial loss of remanence of 1% for irradiation at 350 K to a fluence of 1015 n/cm2. Both SmCo5 and Sm2Co17 magnets showed excellent resistance to radiatifg-induied loss of remanence for neutron irradiation to a fluence of 2.6×1018 n/cm2. Results for gamma radiation showed no loss of remanence for a dose of about 49 Mrad using a 60Co source. Possible mechanisms for radiation-induced loss of magnetic properties are discussed.

In situ TEM studies of irradiation effects for materials improvement

1991 ◽  
Vol 49 ◽  
pp. 452-453
Author(s):  
Charles W. Allen
Keyword(s):  
Nuclear Reactor ◽  
Austenitic Stainless Steels ◽  
High Energy ◽  
Point Of View ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Tem Analysis ◽  
Radiation Induced ◽  
Analytical Tools

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.

Xenon ion irradiation of superconducting YBa2Cu3O7 thin films

1990 ◽  
Vol 48 (4) ◽  
pp. 92-93
Author(s):  
H. Watanabe ◽  
B. Kabius ◽  
B. Roas ◽  
K. Urban
Keyword(s):  
Defect Formation ◽  
Ion Irradiation ◽  
High Resolution Electron Microscopy ◽  
Structural Disorder ◽  
Flux Lines ◽  
Pinning Effect ◽  
Magnetic Flux Lines ◽  
Resolution Electron ◽  
Radiation Induced ◽  
Induced Defects

Recently it was reported that the critical current density(Jc) of YBa2Cu2O7, in the presence of magnetic field, is enhanced by ion irradiation. The enhancement is thought to be due to the pinning of the magnetic flux lines by radiation-induced defects or by structural disorder. The aim of the present study was to understand the fundamental mechanisms of the defect formation in association with the pinning effect in YBa2Cu3O7 by means of high-resolution electron microscopy(HRTEM).The YBa2Cu3O7 specimens were prepared by laser ablation in an insitu process. During deposition, a substrate temperature and oxygen atmosphere were kept at about 1073 K and 0.4 mbar, respectively. In this way high quality epitaxially films can be obtained with the caxis parallel to the <100 > SrTiO3 substrate normal. The specimens were irradiated at a temperature of 77 K with 173 MeV Xe ions up to a dose of 3.0 × 1016 m−2.

scholarly journals A comprehensive review of the influences of nanoparticles as a fuel additive in an internal combustion engine (ICE)

2020 ◽  
Vol 9 (1) ◽  
pp. 1326-1349
Author(s):  
Siti Nurul Akmal Yusof ◽  
Nor Azwadi Che Sidik ◽  
Yutaka Asako ◽  
Wan Mohd. Arif Aziz Japar ◽  
Saiful Bahri Mohamed ◽  
...  
Keyword(s):  
Combustion Engine ◽  
Wide Spectrum ◽  
High Energy ◽  
Combustion Efficiency ◽  
Fuel Properties ◽  
Future Research ◽  
Biodiesel Fuel ◽  
Fuel Additive ◽  
Engine Combustion ◽  
Research Findings

Abstract Nanofluid is a colloidal mixture consisting of nano-sized particles dispersed in a liquid medium. It improves heat transfer properties and promotes high energy efficiency in a wide spectrum of engineering applications. In recent years, particularly in the automotive industry, the addition of nanofluid in diesel/biodiesel as an additive for ICE has become an attractive approach to promote enhanced combustion efficiency and emission reduction due to their superior thermophysical properties. Many researchers have previously demonstrated that the addition of nanoparticles in diesel/biodiesel fuel improved the overall engine combustion characteristics. As a whole, this study aims to summarize the recent research findings related to the effect of nanoparticles on the fuel properties and engine combustion efficiency. Furthermore, different types of additive blended with varying fuel properties are also compared and discussed. Lastly, the advantages and prospects of using nanofluid as an additive fuel are summarized for future research opportunities.

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