Line identification of boron and nitrogen emissions in EUV and VUV wavelength ranges in the impurity powder dropping experiments of LHD and its application to spectroscopic diagnostics

Oishi, Tetsutarou; Ashikawa, N.; Nespoli, F.; Masuzaki, S.; Shoji, M.; Gilson, Erik; Lunsford, R.; Morita, S.; Goto, M.; Kawamoto, Yasuko; Suzuki, C.; Sun, Zhuo; Nagy, A.; Gates, D.; Morisaki, T.

doi:10.1088/2058-6272/abfd88

Cited by 10 publications

(10 citation statements)

References 22 publications

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“…Lower ionization states density peaks close to the toroidal position of the IPD ϕ 0 = 29.75 • (vertical dashed line in figure 3(c)), while for increasing ionization states the density distribution gets progressively more uniform in the toroidal direction. This is consistent with the fact that EUV [30] and CXS measurements, performed approximately 180 • apart toroidally, representative of B 4+ and B 5+ population respectively, exhibit a similar evolution in time, as previously reported in [17]. Also for this case, most of the B ions reach into the confined region and are completely ionized.…”

Section: Modeling Of Powder Penetrationsupporting

confidence: 91%

A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

et al. 2023

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Recently an improved confinement regime, characterized by reduced turbulent fluctuations has been observed in the Large Helical Device upon the injection of boron powder into the plasma [F. Nespoli et al., Nature Physics 2022]. In this article, we report in more detail the experimental observations of increased plasma temperature and the decrease of turbulent fluctuations across the plasma crosssection, on an extended database. In particular, we compare powders of different materials (B, C, BN), finding similar temperature improvement and turbulence response for the three cases. Modeling of the powder penetration into the plasma and of neoclassical electric field and fluxes support the interpretation of the experimental results. Additionally, we report evidence of the temperature improvement increasing with powder injection rates and decreasing for both increasing density and heating power. Though, plasma turbulence response varies depending on the initial conditions of the plasma, making difficult to draw an inclusive description of the phenomenon.

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Section: Modeling Of Powder Penetrationsupporting

confidence: 91%

A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

et al. 2023

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“…Confirmation of positive injection and plasma entrainment is obtained by observation of spectroscopic boron signatures [35] coincident with the period of injection. Figure 5 shows the time evolution of the boron II signal at 136.25 nm in panel (a) and the boron V signal at 4.86 nm in panel (b).…”

Section: Standard Length Dischargesmentioning

confidence: 87%

Real-time wall conditioning and recycling modification utilizing boron and boron nitride powder injections into the Large Helical Device

et al. 2022

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Controlled particulate injections from the PPPL Impurity Powder Dropper(IPD) into the Large Helical Device (LHD) have demonstrated positive effects on the wall conditions in both an intra and inter-shot basis. Injections over a range of densities, input powers, pulse lengths, heating schemes, injection quantities and main ion species show conclusive evidence of improvement to plasma wall conditions. Successful injections are confirmed by both spectroscopic measurements as well as real-time visible camera signals. In 7s long plasmas the responses include a reduction in wall recycling as well as a reduction in native impurity content as observed over the course of several discharges. For plasmas longer than 40s, improvements to the recycling rate and increased impurity control are observed in real time as a consequence of the extended particulate injections. These experiments demonstrate the extended applicability of this solid particulate conditioning technique to the control and maintenance of the plasma wall conditions. In addition they are an important initial step in the development of the real time boronization technique as a supplement to standard conditioning scenarios.

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“…The magnetic field direction for d is reversed with respect to a-c. it enters the plasma, where it is heated and evaporates. The effective injection and vaporization of the powder is confirmed by the sharp increase in the BV line measured by ultraviolet spectroscopy [12]. Due to the extra electron source, the line-averaged electron density n e,av starts to increase.…”

Section: Resultsmentioning

confidence: 76%

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

Nespoli¹,

Masuzaki²,

Tanaka³

et al. 2021

Preprint

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We report the first observation of a novel confinement regime in a stellarator plasma, characterized by increased confinement and reduced turbulent fluctuations. The transition to this new regime is driven by the injection of sub-millimetric boron powder grains into the plasma. With the line averaged electron density being kept constant, substantial increase of stored energy, electron and ion temperature have been observed. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range 100 ≤ f [kHz] ≤ 200 are excited. The access to this regime has been observed for different heating schemes, namely with both electron and ion cyclotron resonant radio frequency, and neutral beams, for both directions of the magnetic field, and for both hydrogen and deuterium plasmas.

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Line identification of boron and nitrogen emissions in EUV and VUV wavelength ranges in the impurity powder dropping experiments of LHD and its application to spectroscopic diagnostics

Abstract: Line identification of boron and nitrogen emissions in EUV andVUV wavelength ranges in the impurity powder dropping experiments of LHD and its application to spectroscopic diagnostics

Cited by 10 publications

References 22 publications

A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

A reduced-turbulence regime in the Large Helical Device upon injection of low-Z materials powders

Real-time wall conditioning and recycling modification utilizing boron and boron nitride powder injections into the Large Helical Device

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

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