2019, Tokitani, M., Ogorodnikova, O. V., Klimov, K. S., Poskakalov, A. G., Kaziev, A. V., Kharkov, M. M., Efimov, V. S., Gasparyan, Y. M., Volkov, N. V., Alimov, V. K., Огородникова, Ольга Вячеславовна, Климов, Николай Сергеевич, Казиев, Андрей Викторович, Харьков, Максим Михайлович, Ефимов, Виталий Сергеевич, Гаспарян, Юрий Микаэлович

© 2018 Elsevier B.V. In the present work, helium (He) was incorporated into tungsten (W) samples by inductively coupled plasma (ICP) source above the threshold of He-induced W ‘fuzz’ formation on W surface. Then, W samples with and without nano-structured W ‘fuzz’ were exposed to pulsed heat loads using deuterium (D) plasma in quasi-stationary high-current plasma gun QSPA-T. The pulse duration was 1 ms and number of pulses was varied from one to thirty to simulate ITER transient events with surface heat load parameters relevant to edge-localized-mode (ELM) impacts. The irradiation was performed below and above the W melting threshold. The D and He retention in each irradiated sample was measured by a method of thermal desorption spectroscopy. We examined the impact of (i) ELMs-like events and (ii) formation of He-induced nano-structured ‘fuzz’ on the D retention in W. We found that the D retention was the highest for samples irradiated by plasma gun above the melting threshold after thirty pulses. Moreover, the D retention after 10 pulses of deuterium plasma gun exposure was higher than that after stationary low-energy plasma exposure at sample temperature of either 600 or 700 K indicating the dominate influence of ELM's-like events on the D retention compared to normal operation regime. The D retention in W samples with the presence of He-induced W ‘fuzz’ was slightly smaller than without that after one pulse of plasma gun exposure with heat load below the W melting temperature. The W ‘fuzz’ was not disappear in this loading conditions, only the length and thickness of nano-structured W fibres were reduced by factors of ∼4 and ∼2, respectively. The He concentration in W with W ‘fuzz’ was decreased by a factor of about 3 after one pulse of plasma gun exposure. The results obtained give possibility to assess the particle retention in divertor areas subjected to high thermal loads at different operation regimes.

2021, Ogorodnikova, O. V., Klimov, N. S., Gasparyan, Yu. M., Harutyunyan, Z. R., Efimov, V. S., Kovalenko, D., Gutarov, K., Poskakalov, А. G., Kharkov, M. M., Kaziev, A. V., Харьков, Максим Михайлович, Гаспарян, Юрий Микаэлович, Казиев, Андрей Викторович, Ефимов, Виталий Сергеевич, Огородникова, Ольга Вячеславовна

In a thermonuclear reactor, materials will be irradiated with hydrogen isotopes and helium (He), neutrons, and heat fluxes. Tungsten (W) and dense nano-structured tungsten (CMSII) coatings are used as plasma-facing materials in current tokamaks and suggested to be used for future fusion devices. In this regard, the study of the accumulation of He and deuterium (D) in W based materials and corresponding surface modifications under normal operation conditions and transient events appears necessary for assessment of safety of fusion reactor due to the radioactivity of tritium and material performance and for the plasma fuel balance. Therefore, in this work, irradiation of W-based materials with D and He ions in stationary regime and in quasi-stationary high-current plasma gun QSPA-T below and above the melting threshold has been performed. In QSPA-T, a pulse duration was 1 ms and number of pulses was varied from one to thirty. In stationary plasma loads, ion energy was varied from 20 to 3 keV, temperature 300-1200 K and flux/fluence 1017-1021 at/m2s/1020-1025 at/m2.

2019, Kaziev, A. V., Kolodko, D. V., Ageychenkov, D. G., Tumarkin, A. V., Kharkov, M. M., Stepanova, T. V., Казиев, Андрей Викторович, Колодко, Добрыня Вячеславич, Агейченков, Дмитрий Григорьевич, Тумаркин, Александр Владимирович, Харьков, Максим Михайлович, Степанова, Татьяна Владимировна

In present contribution we report the first direct measurements of ion fluxes in a nonsputtering magnetron discharge (NSMD) with Al cathode in Ar/O-2 mixtures. The diagnostic unit comprising three-electrode electrostatic lens ion extractor, magnetic sector mass-analyzer, and a vacuum electron multiplier was calibrated and then used to record the time-resolved ion counts of Al+ and Ar+ both in NSMD and arc regimes. The results clearly indicate that in NSMD the dominant species are Ar ions while Al ion signal is lower than the sensitivity limit due to noise level, in contrast to the arc discharge. The capabilities of the diagnostics setup and its sensitivity limits are discussed.