Microstructure evolution in tungsten during low-energy helium ion irradiation

Iwakiri, Hirotomo; Yasunaga, Kōjirō; Morishita, Kazunori; Yoshida, N.

doi:10.1016/s0022-3115(00)00289-0

Cited by 351 publications

(199 citation statements)

References 17 publications

Supporting

Mentioning

180

Contrasting

Unclassified

Order By: Relevance

“…The most stable configuration for He atoms, all of them in interstitial position, is in a platelet configuration at 0 K [66]. The high binding energies indicate that these clusters are stable at temperatures under 500 K. This is in agreement with platelets experimentally observed by Iwakiri et al [45], after irradiating W with 0.25 keV He ions at 293 K, as they observed platelets formed by He atoms. In the case of mixed He-SIA clusters (He n I m ), the binding energies proposed by Becquart et al [66] have been used, i.e., single He atoms bind to SIA (I) and SIA clusters (I n ) with a binding energy of 0.94 eV.…”

Section: Helium In Tungstensupporting

confidence: 89%

“…A possible solution could be the use of nanostrucutred W [43], due to its high grain boundary (GB) density. Nanostructured W is expected to present higher irradiation tolerance [44], as GBs may act as defect sinks for vacancies, SIAs and light species [45][46][47][48]. GBs, on the one hand, might increase the annihilation rate between vacancies and SIAs and, on the other hand, might trap He and H atoms, decreasing their number in the interior of the grains.…”

Section: Acknowledgementsmentioning

confidence: 99%

“…In Ref. [44] it has been reported that grain boundaries act as defect sink for vacancies, SIAs and He atoms, thereby presenting nanostructured W with high grain boundary density is a candidate as material to prove whether it presents superior radiation tolerance than monocrystalline W. At grain boundaries, vacancies and SIAs annihilate [45]. Nanocolumnar W has recently been fabricated with a high grain boundary density [43] and it has been experimentally observed that high grain boundary density has a direct influence in the retention of light species [49].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

Alberdi¹

View full text Add to dashboard Cite

Section: Helium In Tungstensupporting

confidence: 89%

Section: Acknowledgementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

Alberdi¹

View full text Add to dashboard Cite

“…In addition, we have to determine the plasma and device operations that affect the reflectivity. Various plasma-surface interactions contribute to the degradation of the reflectivity: deposition of impurities (metal, carbon) on the surface [1], sputtering by ions and charge exchange particles [2], and the formation of bubbles and blisters on the surface layer [3]. These interactions depend on the plasma conditions (main discharge, glow discharge cleaning and working gas), in-vessel conditions (wall and divertor materials and the wall temperature), and mirror location.…”

Section: Introductionmentioning

confidence: 99%

Impurity Deposition on a First Mirror Surface during Hydrogen Discharges in LHD

Akiyama

Yoshida

Tokitani

et al. 2013

Plasma and Fusion Research

View full text Add to dashboard Cite

First mirrors in fusion devices have to retain the reflectivity and the degradation mechanism and dominant plasma operations that affect the reflectivity have to be understood. The reflectivity of visible laser light (635 nm) of a corner cube mirror is almost entirely determined by the initial hydrogen glow discharges for wall conditioning before conducting a main plasma experiment in the Large Helical Devices (LHD). The hydrogen glow discharge forms a carbon deposition layer on the mirror surface, which degrades its reflectivity. A neon glow discharge and subsequent main discharges had less effect.

show abstract

“…[9], in a linear divertor plasma simulator device, it should be noted that bombarding helium atoms could create bubbles on the surface of tungsten even if their energy (< 50 eV) was much below the sputtering threshold energy (~ 0.4 keV). It was also found that the bubbles could be formed even at high temperature (~ 1,000 K) [10]. The fact that helium bubbles are remarkably formed at high temperature in tungsten even if the energy of the helium is less than or near the threshold energy for displacement damage suggests the enhancement of hydrogen trapping and difficulty controlling the recycling process for the hydrogen isotope during the burning plasma discharge.…”

Section: Introductionmentioning

confidence: 99%

Physics and Technological Issues for Steady-State Tokamak Operation on TRIAM-1M

Zushi

Itoh

Yoshida

et al. 2003

J. Plasma Fusion Res.

View full text Add to dashboard Cite

Subjects on TRIAM-1M are presented from the viewpoint of plasma physics and reactor technology associated with 'steady state operation' (SSO). For a future fusion power plant, for burning plasma, complete steady state operation is required. Control of the density under the complicated plasma-wall interaction, non-inductive current start-up, and sustainment of high performance are key areas in the present and future investigations.The following experimental results are reviewed. First, it is shown that the co-deposition of the metallic impurity and oxygen plays an important role in the temporary change in the wall pumping rate, and a model of the co-deposition probability agreed with the observation. It was also noticed that the thermal release of the hydrogen from the plasma-facing components affects the steady state density operation in the ultra long discharge. It was found that enhanced influx of metal impurities from the hot spot affect the steady state operation of the high performance plasma. Second, helium effects on microscopic damage on metals were studied in helium/hydrogen mixture discharges. A large quantity of dislocation loops and dense fine bubbles were observed by means of TEM even for exposure only 125 seconds in duration. From TDS for the specimens, the amount of retained helium was evaluated to be 3.9 × 10 20 He/m 2 . Third, the physics understanding for the enhanced current drive (ECD) mode around the threshold power level progressed from the viewpoint of transition probability. The forward transition frequency from a non-ECD plasma state to the ECD state was precisely determined under fixed LHCD power. Thus, a statistical probability for ECD transition was determined; that is, the transition behavior around the threshold power could be described in a statistical manner. Transition frequency showed a strong power dependence. Fourth, the current ramp-up scenario without using centre solenoid coils was reinvestigated at higher density, and controllability of the current ramp-up rate was studied. The plasma was initiated by ECH (fundamental O-mode at 170 GHz with 200 kW) at B = 6.7 T, and a ramp-up rate below the technical limit of 150 kA/s for ITER could be achieved by choosing LH power. A model to describe the ramp-up is proposed.

show abstract

Microstructure evolution in tungsten during low-energy helium ion irradiation

Cited by 351 publications

References 17 publications

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

Impurity Deposition on a First Mirror Surface during Hydrogen Discharges in LHD

Physics and Technological Issues for Steady-State Tokamak Operation on TRIAM-1M

Contact Info

Product

Resources

About