Investigation of hydrogen recycling in long-duration discharges and its modification with a hot wall in the spherical tokamak QUEST

Hanada, K.; Yoshida, N.; Honda, Takeshi; Wang, Z.; Kuzmin, A.; Takagi, Ikuji; Hirata, Takashi; Oya, Yasuhisa; Miyamoto, M.; Zushi, H.; Hasegawa, Makoto; Nakamura, K.; Fujisawa, A.; Idei, H.; Nagashima, Yoshihiko; Watanabe, Osamu; Onchi, Takumi; Kuroda, Kengoh; Long, H.; Watanabe, Hideo; Tokunaga, Kazutoshi; Higashijima, A.; Shoji, K.; Nagata, T.; Takase, Y.; Fukuyama, A.; Mitarai, O.

doi:10.1088/1741-4326/aa8121

Cited by 40 publications

(36 citation statements)

References 38 publications

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“…In order to validate this assumption, transport analysis by 2D Monte Carlo code is needed and is now underway. Based on these assumptions and simplifications, we set main input parameters as follows: V M = 12.8 m 3 , A Wall + A Lim = 26.5 m 2 , d Wall = 50 nm, T e = T i = 10 eV,

T_{H_{2}} = 0.01 eV

, T H = 0.1 eV.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…The symbol

{\overset{S}{true}}_{H_{2}}^{Wall / Lim}

is the molecular source by the outflux from the wall and limiter, that is, recycling source, expressed with small thick arrows (v) in Figure c. This term is equal to the loss term in the wall/limiter model, so we calculate it with the wall and limiter surface model described later in section 2.3. In addition,

{\overset{S}{true}}_{H_{2}}^{gain}

and

{\overset{S}{true}}_{H_{2}}^{loss}

are the molecular source and sink due to molecular and atomic processes in the gas phase, respectively (Figure c‐i).…”

Section: Model Equations For the Particle Balancementioning

confidence: 99%

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Modelling of plasma and its wall interaction for long‐term tokamak operation

Okamoto

Tatsumi

Abe

et al. 2018

Contributions to Plasma Physics

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Metal plasma‐facing materials (PFMs) are expected to be candidates for future fusion power plants from the view point of tritium retention. The purpose of this study is to develop a model including a long timescale plasma interaction with metal PFMs. As a first step, we have developed a simple zero‐dimensional (0D) model, which consists of particle balance equations for the following three different particle species: (a) hydrogen plasma (elec., H+, H2+, H3+), (b) neutral hydrogen atoms (H) and molecules (H2) in the gas phase, and (c) the wall‐stored H atoms. The model has been applied to simulate long‐term operation in the limiter configuration of the QUEST tokamak. Modelling results of the long time evolution of the H atom wall inventory reasonably reproduce the experimental tendency. Although the present model is relatively simple, it is useful to understand the basic characteristics of overall plasma particle balance, the density control of the main plasma, and the H atom wall inventory for long‐term tokamak operation.

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T_{H_{2}} = 0.01 eV

, T H = 0.1 eV.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…The symbol

{\overset{S}{true}}_{H_{2}}^{Wall / Lim}

{\overset{S}{true}}_{H_{2}}^{gain}

and

{\overset{S}{true}}_{H_{2}}^{loss}

are the molecular source and sink due to molecular and atomic processes in the gas phase, respectively (Figure c‐i).…”

Section: Model Equations For the Particle Balancementioning

confidence: 99%

Modelling of plasma and its wall interaction for long‐term tokamak operation

Okamoto

Tatsumi

Abe

et al. 2018

Contributions to Plasma Physics

Self Cite

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“…The Q-shu University Experiment with Steady-state Spherical Tokamak (QUEST) is a medium-size spherical tokamak (ST) device [11] with major and minor radii of R = 0.64 m and a = 0.4 m, respectively, and major limiter radii of 0.22 and 1.32 m on the mid-plane. All of the QUEST discharges discussed in this paper were produced in an inboard limiter (IL) configuration [12].…”

Section: Methodsmentioning

confidence: 99%

Fast Tangentially Viewed Soft X-Ray Imaging System Based on Image Intensifier with Microchannel Plate Detector on QUEST

Hanada

Kuroda

Kojima

et al. 2019

Plasma and Fusion Research

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A two-dimensional (2D) soft X-ray (SXR) imaging system for obtaining tangential views of plasmaproduced SXR has been installed on the QUEST tokamak. The system comprises a chevron micro-channel plate (MCP) and a phosphor screen, which together serve as an SXR detector and image intensifier, along with a high-speed video camera for capturing and storing image data. The system can be used in imaging mode to obtain high spatial-and time-resolution images or in photon counting mode at an ultra-high framing rate of 100 kHz to obtain SXR energy spectra. Here, we propose a method of in situ energy calibration based on the transmission characteristics of a 25-µm Be filter. The proposed method was used to obtain SXR spectra in the energy range 1.5-3.5 keV with a core electron temperature in agreement with electron temperatures measured by the Thomson scattering method. Furthermore, oscillations based on the modification of plasma parameters and rapid increases in impurity radiation were detected in imaging mode. This dual-mode-compatible method for obtaining 2D SXR diagnostics is useful for the study of high temperature plasmas.

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“…The calculation of wave propagation and absorption was performed using GENRAY ray-tracing code [14,15]. The magnetic configuration used here is based on the experimental results of the QUEST spherical tokamak [16]. The RF frequency and power are set at 8.2 GHz and 50 kW to model the experimental set-up of the 8.2-GHz HFS Xmode in QUEST.…”

Section: Introductionmentioning

confidence: 99%

High-Field-Side RF Injection for Excitation of Electron Bernstein Waves

Yoneda

Hanada

Elserafy

et al. 2018

Plasma and Fusion Research

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An evaluation of high-field-side (HFS) X-mode injection for the electron-Bernstein-wave (EBW) scenario is performed using the GENRAY ray-tracing code. In the early stage of low-density plasma start-up, when the electron cyclotron resonance and upper hybrid resonance layers are close to each other, efficient and localized heating by the EBW is attainable. We show that, when the electron density rises, the HFS scenario spontaneously shifts to current drive with successful electron heating. This shift can be explained as a change in heating mechanism from collisional to electron cyclotron damping. Also, we discuss a possible OX -B scenario to continue the plasma current drive beyond the formation of an over-dense plasma.

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Investigation of hydrogen recycling in long-duration discharges and its modification with a hot wall in the spherical tokamak QUEST

Cited by 40 publications

References 38 publications

Modelling of plasma and its wall interaction for long‐term tokamak operation

Modelling of plasma and its wall interaction for long‐term tokamak operation

Fast Tangentially Viewed Soft X-Ray Imaging System Based on Image Intensifier with Microchannel Plate Detector on QUEST

High-Field-Side RF Injection for Excitation of Electron Bernstein Waves

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