scholarly journals A new mechanism for void-cascade interaction from nondestructive depth-resolved atomic-scale measurements of ion irradiation–induced defects in Fe

2020 ◽  
Vol 6 (31) ◽  
pp. eaba8437 ◽  
Author(s):  
S. Agarwal ◽  
M. O. Liedke ◽  
A. C. L. Jones ◽  
E. Reed ◽  
A. A. Kohnert ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Ion Irradiation ◽  
Atomic Scale ◽  
High Porosity ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Transmission Electron ◽  
Nondestructive Investigation ◽  
Cascade Interaction ◽  
Induced Defects

The nondestructive investigation of single vacancies and vacancy clusters in ion-irradiated samples requires a depth-resolved probe with atomic sensitivity to defects. The recent development of short-pulsed positron beams provides such a probe. Here, we combine depth-resolved Doppler broadening and positron annihilation lifetime spectroscopies to identify vacancy clusters in ion-irradiated Fe and measure their density as a function of depth. Despite large concentrations of dislocations and voids in the pristine samples, positron annihilation measurements uncovered the structure of vacancy clusters and the change in their size and density with irradiation dose. When combined with transmission electron microscopy measurements, the study demonstrates an association between the increase in the density of small vacancy clusters with irradiation and a remarkable reduction in the size of large voids. This, previously unknown, mechanism for the interaction of cascade damage with voids in ion-irradiated materials is a consequence of the high porosity of the initial microstructure.

scholarly journals Thermal kinetics of micro-defects in He-ion implanted W and W5Re alloys

Tungsten ◽  
2021 ◽  
Author(s):  
Yong-Li Liu ◽  
Ya-Min Song ◽  
Lei Li ◽  
Ruo-Yu Bai ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Annealing Temperature ◽  
Thermal Evolution ◽  
Ion Irradiation ◽  
Positron Annihilation Spectroscopy ◽  
Vacancy Cluster ◽  
Dislocation Loops ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Nucleation Sites

AbstractTo investigate the thermal evolution of vacancy-type defects in He-ion irradiated W and W5Re alloy, different isochronal annealing treatments from 373 to 1273 K were conducted on the irradiated materials. Positron annihilation spectroscopy including positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy were mainly used to characterize the micro-defects evolution. The results showed that the thermal evolution characteristics of defects in both W and W5Re were similar. After He-ion irradiation, mono-vacancies with positron annihilation lifetime of ~ 190 ps were detected in W, together with a large amount of dislocation loops with positron annihilation lifetime of ~ 150 ps in W5Re alloys. The coarsening of vacancy clusters at the expense of small vacancy clusters was the main thermal evolution feature of vacancy-type defects in both W and W5Re when annealing temperature increased to 1073 K. In this progress, the positron annihilation lifetime increased to ~ 350 ps (clusters composed of 4 –8 mono-vacancies) in both W and W5Re. As the temperature increased to 1273 K, the positron annihilation lifetime decreased to ~ 240 ps, which was attributed to a significant population reduction of the dislocation loops, the dissociation of large HenVm complexes and the annealing of micro-voids in both W and W5Re. The vacancy-type defects in W5Re were more susceptible to the annealing temperature because of the formation of vacancy cluster-Re complexes. Re clusters in irradiated W5Re alloy could serve as the nucleation sites of He bubbles, which promoted the swelling and protrusion formation on the surface.

Transmission Electron Microscopy Observation of 11MEV B5+ Ion Irradiation in Bi2Sr2CaCu2O7-x Single Crystal

1999 ◽  
Vol 5 (S2) ◽  
pp. 758-759
Author(s):  
W.L. Zhou ◽  
Y. Sasaki ◽  
Y. Ikuhara ◽  
C.J.O’Connor
Keyword(s):  
Single Crystal ◽  
Ion Irradiation ◽  
Target Material ◽  
Heavy Ion ◽  
Zone Melting ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Different Types ◽  
Induced Defects ◽  
Irradiation Induced Defects

Artificial defects generated by ion irradiation have been considered an efficient method to enhance the critical current density in superconducting materials. The mechanism of producing defects as flux pining centers is still an important issue since the efficiency of irradiation-induced defects in flux pinning strongly depends on their microstructures. Different types of defects have been found in heavy ion irradiation. However, there are few results that show light ion irradiation due to the target material selected, the type of light ion and energy, and the incident ion angle. Another factor is the difficulty of cross-sectional sample preparation. In this paper, a single crystal Bi2Sr2CaCu2O7-x with 11 MeV B5+ ion irradiation was observed by transmission electron microscope (TEM) from both plan and cross-sectional view.The Bi2Sr2CaCu2O7-x single crystals used for ion irradiation were prepared using the floating-zone melting method. The crystals were cleaved into thin sheets of about 20 μm thickness along the a-b plane and cut to about 2mmx2mm size.

scholarly journals Effect of He-appm/DPA ratio on the damage microstructure of tungsten

MRS Advances ◽  
2016 ◽  
Vol 1 (42) ◽  
pp. 2893-2899 ◽  
Author(s):  
R.W. Harrison ◽  
H. Amari ◽  
G. Greaves ◽  
J.A. Hinks ◽  
S.E. Donnelly
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
Dislocation Loops ◽  
Vacancy Clusters ◽  
Transmission Electron ◽  
Damage Structure ◽  
Ordered Array ◽  
20 Nm

AbstractIn-situ ion irradiation and transmission electron microscopy has been used to examine the effects of the He appm to DPA ratio, temperature and dose on the damage structure of tungsten (W). Irradiations were performed with 15 or 60 keV He+ ions, achieving He-appm/displacements per atom (DPA) ratios of ∼40,000 and ∼2000, respectively, at temperatures between 500 and 1000°C to a dose of ∼3 DPA. A high number of small dislocation loops with sizes around 5–20 nm and a He bubble lattice were observed for both He-appm/DPA ratios at 500°C with a bubble size ∼1.5 nm. Using the g.b=0 criterion the loops were characterised as b = ±1/2<111> type. At 750°C bubbles do not form an ordered array and are larger in size compared to the irradiations at 500°C, with a diameter of ∼3 nm. Fewer dislocation loops were observed at this temperature and were also characterised to be b = ±1/2<111> type. At 1000°C, no dislocation loops were observed and bubbles grew as a function of fluence attributed to vacancy mobility being higher and vacancy clusters becoming mobile.

scholarly journals Detection of Atomic Scale Changes in the Free Volume Void Size of Three-Dimensional Colorectal Cancer Cell Culture Using Positron Annihilation Lifetime Spectroscopy

PLoS ONE ◽  
2014 ◽  
Vol 9 (1) ◽  
pp. e83838 ◽  
Author(s):  
Eneko Axpe ◽  
Tamara Lopez-Euba ◽  
Ainara Castellanos-Rubio ◽  
David Merida ◽  
Jose Angel Garcia ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Cell Culture ◽  
Positron Annihilation ◽  
Free Volume ◽  
Cancer Cell ◽  
Three Dimensional ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Atomic Scale ◽  
Void Size ◽  
Positron Annihilation Lifetime

Non Destructive Examination of Helium Implanted Fe-Cr Model Alloys

2009 ◽  
Author(s):  
V. Krsjak ◽  
S. Sojak ◽  
M. Petriska ◽  
J. Veternikova
Keyword(s):  
Chromium Content ◽  
Local Damage ◽  
Martensitic Steels ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Cr Content ◽  
Helium Implantation ◽  
Displacement Per Atom ◽  
Induced Defects ◽  
Non Destructive

The helium implantation has been successfully used for the obtaining of radiation damage in different Fe-Cr ferritic/martensitic steels. Implanted doses within the range 6.24×1017 – 3.12×1018 cm−2 corresponding to local damage up to 90 DPA (Displacement per Atom) were acquired in a thin (&lt;1 μm) region. For observing the dependence of vacancy-type defects on the load and the chromium content, positron annihilation lifetime spectroscopy (PALS) has been used. Experiments showed that chromium had a significant effect on the radiation treated microstructures of the materials. In particular, chromium influences the size and density of the implantation induced defects and specific Cr content should prevent the formation of vacancy clusters.

Speciation of uranium and doping induced defects in Gd1.98U0.02Zr2O7: Photoluminescence, X-ray photoelectron and positron annihilation lifetime spectroscopy

2017 ◽  
Vol 669 ◽  
pp. 245-250 ◽  
Author(s):  
Santosh K. Gupta ◽  
C. Reghukumar ◽  
Nimai Pathak ◽  
K. Sudarshan ◽  
D. Tyagi ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
X Ray ◽  
Positron Annihilation Lifetime ◽  
Induced Defects

Recent Progress on the Positron Annihilation Experiments on Irradiated Ferritic/Martensitic Steels Containing Helium

2021 ◽  
Vol 1024 ◽  
pp. 1-12
Author(s):  
Vladimir Krsjak
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Neutron Irradiation ◽  
Early Stage ◽  
High Sensitivity ◽  
Positron Annihilation Spectroscopy ◽  
Martensitic Steels ◽  
Positron Annihilation Lifetime ◽  
Induced Defects

The well-known and often acceptable radiation tolerance of ferritic/martensitic (f/m) steels can be severely diminished when neutron irradiation is accompanied by the production of helium. The presence of helium in the irradiated materials changes the kinetics of the nucleation, recombination, and clustering of the radiation-induced defects. High production rates of helium may lead to a non-negligible volumetric bubble swelling at relatively low temperatures. Extrapolation of the knowledge gained from neutron irradiation experiments to fusion or spallation environments is additionally complicated due to the unknown and comprehensive effects of dpa rate, temperature, the presence of sinks in the crystal lattice and others. To improve the understanding of the microstructure and irradiation parameters effects, close attention must be paid to the early stages of the radiation damage. It is expected that the pre-existing vacancy-type defects, attributed to lattice distortion at the grain/subgrain boundaries and oxide-matrix interfaces, are effective sinks for primary defects and helium, i.e. they control the formation and growth of helium-vacancy agglomerations. This early-stage radiation damage, however, cannot be captured by conventional transmission electron microscopy, and thus other experimental techniques are called for. One of the most perspective experimental approaches to investigate small vacancy-type defects, with a high sensitivity to confined helium, is to utilize positron annihilation spectroscopy (PAS). In particular, two spectroscopy techniques, positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS) of the annihilation line, can be beneficially used for the characterization of helium-vacancy clusters. This paper reviews the recent positron annihilation spectroscopy characterization of various irradiation experiments involving helium. Mainly two types of irradiation experiments are addressed, helium implantation and spallation neutron source irradiation experiments. Discussion is aimed at the potential of PAS in the early-stage formation of helium bubbles and the investigation of the effects of irradiation parameters in defect production and accumulation.

EXPERIMENTAL VERIFICATION OF HEAVY ION IRRADIATION SIMULATION

2004 ◽  
Vol 18 (17) ◽  
pp. 881-885 ◽  
Author(s):  
SHENGYUN ZHU ◽  
T. IWATA ◽  
YONGJUN XU ◽  
YONGNAN ZHENG ◽  
DONGMEI ZHOU ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Experimental Verification ◽  
Proton Irradiation ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Equivalent Dose ◽  
Positron Annihilation Lifetime ◽  
Heavy Ion Irradiation ◽  
Good Agreement

The heavy ion irradiation simulation of neutron and/or proton irradiation has been verified experimentally by the detailed study of radiation damage in α- Al 2 O 3 irradiated at the equivalent dose by 5.28×1015 cm -285 MeV 19 F ions and by 3×1020 cm -2 En≥1 MeV neutrons, respectively. The radiation damage created by irradiation was examined by a positron annihilation lifetime technique. The positron annihilation parameters of lifetime and intensity obtained for both irradiations in α- Al 2 O 3 are all in good agreement. This demonstrates that the heavy ion irradiation can well simulate the neutron and/or proton irradiation.

Free-Volume Properties of Amorphous Polymers Probed by Positron Annihilation Spectroscopy

1990 ◽  
Vol 215 ◽  
Author(s):  
Y. C. Jean ◽  
F. Zandiehnadem ◽  
Q. Deng
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Amorphous Materials ◽  
Polymeric Materials ◽  
Positron Annihilation Spectroscopy ◽  
Atomic Scale ◽  
Annihilation Radiation ◽  
Positron Annihilation Lifetime ◽  
Additional Information ◽  
Volume Properties

AbstractPositron annihilation spectroscopy (PAS) has been developed to characterize the free-volume properties of polymers. Positron annihilation lifetime measurements give direct information about the dimension, content, and hole-size distributions of free-volume in amorphous materials. The angular correlation of positron annihilation radiation measurements give additional information about the shape of the free-volume holes in oriented polymeric materials. The unique capability of PAS to probe free-volume properties is from the fact that positronium atom is preferentially trapped in the atomic-scale holes which have a size ranging from 1 to 10 Å.

Studies of Defects in ZnO by Positron Annihilation

1995 ◽  
Vol 378 ◽  
Author(s):  
Werner Puff ◽  
Sebastian Brunner ◽  
Peter Mascher ◽  
Adam G. Balogh
Keyword(s):  
Positron Annihilation ◽  
Colour Change ◽  
Doppler Broadening ◽  
Positron Annihilation Lifetime ◽  
Dark Orange ◽  
Radiation Induced ◽  
Induced Defects ◽  
Annealing Experiments ◽  
Mev Protons ◽  
Yellowish White

AbstractIn order to investigate the basic properties of radiation-induced defects in ZnO crystals, positron annihilation lifetime and Doppler-broadening measurements were performed on crystals sinterd for 18 hours at 1200 °C and irradiated with 3 MeV protons at 223 K. The irradiation induced a colour change of the specimens from the original yellowish-white to dark orange or even brown. Isochronal annealing experiments showed three annealing stages, centred at about 150 °C, 500 – 550 °C, and 750 °C, respectively. These stages are related to the annealing of variously sized vacancy complexes.

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