Short positron lifetime at vacancies observed in electron-irradiated tungsten: Experiments and first-principles calculations

Yabuuchi, Youichi; Tanaka, Minoru; Kinomura, A.

doi:10.1016/j.jnucmat.2020.152473

Cited by 16 publications

(5 citation statements)

References 51 publications

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“…As the fluence increases the defect concentration also increases leading to a higher k d and a lower τ 1 , which is observed in the 3 MeV He-irradiated samples. Similar results were also observed in electron-and neutron-irradiated samples [31][32][33]. The τ 2 value of the low fluence He-irradiated (HeLF) sample was 202 ± 6 ps with an intensity I 2 of about 66%.…”

Section: Defect Analysis Using Pals and Temsupporting

confidence: 81%

Studies on the role of ion mass and energy in the defect production in irradiation experiments in tungsten

et al. 2021

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Experimental investigations on the role of ion mass and the primary knock-on atoms (PKA) spectrum in the defect type, structure and defect production efficiency is presented in ion-irradiation experiments in tungsten using a combination of positron annihilation spectroscopy, transmission electron microscopy and secondary ion mass spectroscopy. Recrystallized tungsten foils were irradiated using low- (helium), medium- (boron) and high-mass (gold) ions of MeV energy for a comparable dpa and implantation range at room temperature. Depending on the ion mass and the PKA spectrum, distinctly different defect structures were observed at the atomistic as well as meso-scales. While no indication of dislocation lines was observed in 3 MeV helium irradiated samples, the boron and gold ions showed extensive dislocation line formation. The cluster shape depends on the PKA energy and the cluster density depends on the irradiation fluence. The depth profile analysis of the defects in the helium-irradiated samples showed extensive helium trapping throughout the implantation range. Significant sub-surface helium trapping is observed within 700 nm from the surface, indicating that they moved towards the surface from their mean implantation depth of 4500 nm. The study also shows a correlation between carbon and helium profiles in the samples.

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Section: Defect Analysis Using Pals and Temsupporting

confidence: 81%

Studies on the role of ion mass and energy in the defect production in irradiation experiments in tungsten

et al. 2021

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“…Its value was found (171±16) ps for the sheet and (185±8) ps for the bar with relative intensity, I 1 , of (75±16)% and (45±3)% (figure 1(b)), respectively. The lifetimes for mono-vacancy and dislocation defects are reported in the range of 160-200 ps and 130-180 ps, respectively [33,34,[38][39][40]. Also, the positron lifetime of a vacancy associated with either screw or edge dislocation was calculated in the range from 188 to 192 ps [36].…”

Section: Positron Annihilation Lifetime Spectroscopy (Pals)mentioning

confidence: 99%

Neutron irradiation effects in different tungsten microstructures

et al. 2021

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In this work the correlation of the neutron radiation damage and tungsten (W) microstructure is investigated. Further, the modification of the structure as a result of the neutron irradiation is assessed and its effect on the mechanical properties is determined. Forged bar (ITER grade), cold rolled sheet, and single crystalline tungsten materials were neutron irradiated at 600 °C to a damage of 0.12 displacements per atom. Neutron irradiation results in the formation of voids of almost the same size (larger than 1 nm) and dislocations detected by positron annihilation lifetime spectroscopy. All W grades have similar total dislocation densities, in the range of (1.6-2.4)×10 14 m −2 , as determined by electrical resistivity measurements. After irradiation the hardness of all tungsten grades increases and the largest increase is that of the single crystal (47%), whereas the smallest that of the sheet (13%). Increase in the yield strength, correlated to the increase of the hardness, is also found. The largest increase is observed for the single crystal (25%) and the smallest for the sheet (6%). The different degrees of hardening and strengthening indicate that the microstructure of the different tungsten grades has a significant influence on their neutron radiation damage resistance.

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“…The lifetime that corresponds to the defect-free W materials is reported to be in the range 100-116 ps [53,54,55,56,57,58,59]. The lifetimes for mono-vacancy and dislocation defects are reported in the range of 160-200 ps and 130 -180 ps, respectively [42,55,56,60,61]. The low lifetime value of 130 ps corresponds to screw dislocation as calculated by Staikov et al [58].…”

Section: Open Volume Defects Using Palsmentioning

confidence: 88%

“…The lifetime, 1  , after irradiation at 600 C is (163 ± 1) ps, close to that found for the unirradiated sample ((170 ± 1) ps). The defects associated with this lifetime in both the unirradiated and irradiated samples are dislocations [42,55,56,60,61]. As the irradiation temperature increases to 800 C 1  increases to (205 ± 2) ps.…”

Section: Open Volume Defects Using Palsmentioning

confidence: 96%

“…Yabuuchi at al. [61] calculated a positron lifetime of ~170 ps for the V-C, V-N, and V-O complexes and a lifetime of 169 ps for a monovacancy decorated with two hydrogen atoms (V-2H) and 164 ps for a monovacancy decorated with three hydrogen atoms (V-3H). However, at the irradiation temperature of 1200 C vacancy-hydrogen (V-nH) clusters are not expected to be present because the dissociation of hydrogen from vacancy takes place at much lower temperatures according to thermal desorption spectroscopy studies [65].…”

Section: Open Volume Defects Using Palsmentioning

confidence: 99%

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Evolution of microstructure in neutron irradiated cold rolled tungsten and its correlation with hardness

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et al. 2021

Fusion Engineering and Design

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Short positron lifetime at vacancies observed in electron-irradiated tungsten: Experiments and first-principles calculations

Cited by 16 publications

References 51 publications

Studies on the role of ion mass and energy in the defect production in irradiation experiments in tungsten

Studies on the role of ion mass and energy in the defect production in irradiation experiments in tungsten

Neutron irradiation effects in different tungsten microstructures

Evolution of microstructure in neutron irradiated cold rolled tungsten and its correlation with hardness

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