Vapor shielding effects on energy transfer from plasma-gun generated ELM-like transient loads to material surfaces

Kikuchi, Yusuke; Sakuma, I.; Asai, Yusuke; Onishi, Keizo; Isono, Wataru; Nakazono, Takumi; Nakane, Masato; Fukumoto, N.; Nagata, Masayoshi

doi:10.1088/0031-8949/t167/1/014065

Cited by 10 publications

(7 citation statements)

References 15 publications

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“…At present, experimental simulations of high-energy fluxes from transients expected in fusion reactors are performed using different test-bed devices: e-beam facilities and linear devices [3][4][5][6][7], high energy lasers [4,8,9], powerful pulsed plasma guns and quasi-stationary plasma accelerators (QSPAs) [10,11]. All such facilities are able to achieve, at least in part, the loading conditions of ITER disruption and edge localized modes (ELMs).…”

Section: Nuclear Fusionmentioning

confidence: 99%

Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M

et al. 2019

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The features of plasma energy transfer to material surfaces during plasma–surface interactions (PSIs) in the presence of a strong magnetic field are investigated within the recently developed quasi-stationary plasma accelerator, QSPA-M. This novel PSI test-bed facility can reproduce edge localized mode (ELM) impacts, both in terms of heat load and particle flux to the surface, and provide plasma transportation in an external magnetic field, which mimics the divertor conditions. Investigations of energy transfer to the material surface have been performed for varied plasma heat load and external magnetic field values. Calorimetry, optical emission spectroscopy and high-speed imaging were applied for PSI characterization. For perpendicular plasma incidence, it has been shown that the transient plasma layer is formed in front of the surface by the stopped head of the plasma stream even for rather small plasma heat loads, which do not result in surface melting. The plasma density in this near-surface layer is much higher than in the impacting stream. It leads to the arisen screening effect for energy transfer to the surface. For B = 0, the thickness of the screening layer is less than 3 cm, but it increases to 15 cm when B = 0.8 T. The shielding effect due to the formation of a dense plasma layer in front of the exposed surface should be favorable for material performance, being important for decreasing the overall erosion of plasma-facing components during a large number of repetitive ELMs.

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Section: Nuclear Fusionmentioning

confidence: 99%

Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M

et al. 2019

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“…In this study, the discharge voltage was 2.8 kV and the feeding gas for discharges was helium (He). The strength of the magnetic field produced by the pulsed plasma was typically 0.2 T [3]. The Zeeman effect due to the magnetic field is much smaller than the broadening observed in this study and negligible.…”

mentioning

confidence: 62%

“…One of the most serious issues for plasma facing components will be the impact of transients accompanied by edge localized modes (ELMs) and disruptions [1]. Plasma devices that can produce pulses have been used to investigate the impact of transients including the formation of clacks [2], the effect of vapor shielding [3], and formation of arcing [4]. Characterization of the plasma is important to discuss the effect in a quantitative manner.…”

mentioning

confidence: 99%

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Doppler and Stark Broadenings of He II Emission in NAGDIS-PG

Kajita

Nakamori

Tanaka

et al. 2021

Plasma and Fusion Research

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Time evolutions of the emission from helium (He) ion at 468.6 nm were observed in the magnetized co-axial plasma gun device NAGDIS-PG, and the broadening of the spectrum was analyzed in terms of Doppler and Stark broadenings to deduce the ion temperature and the electron density. A significant broadening of the He II spectrum was identified around a dip in the discharge current, suggesting that increases in the temperature and density occurred.

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“…Vapor generation and reduction of the electron temperature near the Be target were confirmed in PISCES-B experiments and particle-in-cell simulations [3]. The vapor shielding effect was also investigated using the plasma gun devices that can simulate ELM events [4,5]. On the other hand, considering the energy reflection on the material surface, the low-Z materials like Be could easily transfer the plasma energy to the material compared with the high-Z material, because mass ratios of the low-Z material to the main plasma species such as hydrogen isotopes and helium (He) are closer to unity.…”

Section: Introductionmentioning

confidence: 99%

Increased Energy Absorption into W due to the Metal Deposited Layer from an ELM-like Pulsed Plasma

Nakamori

Ohno

Tanaka

et al. 2019

Plasma and Fusion Research

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It is important in divertor physics research to investigate thermal response process of beryllium deposited tungsten to high transient heat load such as ELMs. We investigated the heat load on aluminum-coated tungsten by comparing the measured back surface temperature and calculation results of the one-dimensional heat conduction equation. When the plasma power was low enough so that the evaporation did not occur sufficiently, the heat load on the aluminum-coated tungsten was higher than the virgin tungsten. It was caused by the reduction in the energy reflection coefficient due to the formation of aluminum layer. The results suggested that the beryllium deposited layer adversely affects the heat load on the divertor plate when the heat load was not high such as Grassy-ELM.

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Vapor shielding effects on energy transfer from plasma-gun generated ELM-like transient loads to material surfaces

Cited by 10 publications

References 15 publications

Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M

Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M

Doppler and Stark Broadenings of He II Emission in NAGDIS-PG

Increased Energy Absorption into W due to the Metal Deposited Layer from an ELM-like Pulsed Plasma

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