First boronization in KSTAR: Experiences on carborane

Hong, Suk–Ho; Lee, KunSu; Kim, Kwang Pyo; Kim, Kyung Min; Kim, Hong-Tack; Sun, Jong-Ho; Woo, Hyun-Jong; Park, Jaemin; Park, Eun-Kyong; Kim, Woong-Chae; Kim, Hak-Kun; Park, Kaprai; Yang, H.L.; Oh, Y.K.; Na, Hoon-Kyun; Lho, T.; Chung, Kyu‐Sun

doi:10.1016/j.jnucmat.2010.10.059

Cited by 14 publications

(6 citation statements)

References 13 publications

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“…This confirms that at lower pressure the current density distribution is more steady at the wall surface. The wall current density is an important parameter in glow discharge cleaning and wall-coating using glow discharge in tokamaks [5,23,24]. Therefore, these results give insight for improving GDC systems.…”

Section: Current Density and Ion Flux Measurementsmentioning

confidence: 97%

Experimental measurements of the hollow cathode DC glow discharge parameters in Ar and He plasmas

Omrani

Amrollahi

Iraji

2016

Plasma Sources Sci. Technol.

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In this article, we focus on some of the fundamental parameters of SS316L hollow cathode glow discharge. Four SS316L samples are placed at different locations on the cathode surface and the current passed through them is measured in Ar and He glow discharge plasmas. The wall current densities of Ar and He are in the range of 8-25 µA cm −2 and 8-35 µA cm −2 , respectively. Results also show that with decreasing working pressure, the ion flux and current density distribution on the wall surface becomes more uniform. The ion flux of the Ar and He is in the range of 10 13 to 10 14 − ion cm 2 . Total energy losses of Ar and He are measured at the pressure range of 1.4-5.5 × 10 −2 torr and 3.2-7.1 × 10 −1 , respectively. In both Ar and He, total energy losses decreased with increasing pressure. The secondary electron emission coefficients of Ar and He, which are evaluated for the hallow cathode configuration, are about 0.42 and 0.26, respectively, and are higher in comparison with the plate cathode configuration.

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Section: Current Density and Ion Flux Measurementsmentioning

confidence: 97%

Experimental measurements of the hollow cathode DC glow discharge parameters in Ar and He plasmas

Omrani

Amrollahi

Iraji

2016

Plasma Sources Sci. Technol.

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“…The amount of water and other impurities in the vacuum vessel was dramatically reduced [3]. Nevertheless, there remained several issues such as the homogeneity of the coating in the toroidal direction and the control of the hydrogen (H) level after the boronization using a hydrogen-rich material like carborane.…”

Section: A Vacuum Condition Of Vessel and Cryostatmentioning

confidence: 99%

Key Features in the Operation of KSTAR

Kwak

Kim

et al. 2012

IEEE Trans. Plasma Sci.

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The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb 3 Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb 3 Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350 • C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ ∼ 1.8, δ > 0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B T = 2 T with I p = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.Index Terms-Incoloy, in-vessel control coils (IVCC), Korea superconducting tokamak advanced research (KSTAR), superconducting.

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“…Before the boronization, the water base pressure increases during the operation (label a), as discussed above in the ICWC section, while it is completely suppressed to be low after the boronization (label b). The normalized intensity (divided by n e ) of filterscope measurements for O II and C III at the scrape-off layer (SOL) is decreased by a factor of 2 after the boronization [34,37]. Note that the H 2 level is increased by a factor of 10 in the 2009 campaign which originated from carborane molecules in the vacuum vessel.…”

Section: Boronizationmentioning

confidence: 99%

Initial phase wall conditioning in KSTAR

Hong

Kim

et al. 2011

Nucl. Fusion

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Initial phase wall conditioning in KSTAR is depicted. The KSTAR wall conditioning procedure consists of baking, Glow Discharge Cleaning (GDC), ICRH Wall Conditioning (ICWC), and boronization (Bz). The vessel baking has been performed in order to remove various kinds of impurities including H 2 O, carbon and oxygen for the plasma. The total outgassing rates in the KSTAR campaigns are compared. GDC is regularly performed as standard wall cleaning procedure. Another cleaning technique is ICWC, which is useful for intershot wall conditioning under strong magnetic field. In order to optimize operation time and removal efficiency, parameter scan has been performed. Bz is a standard technique to remove oxygen impurity from vacuum vessel. KSTAR has utilized carborane powder which is non-toxic boron containing material. The first bz has been performed successfully. Water and oxygen level in vacuum vessel have been reduced significantly. Boron containing thin films deposited by boronization are studied.

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First boronization in KSTAR: Experiences on carborane

Cited by 14 publications

References 13 publications

Experimental measurements of the hollow cathode DC glow discharge parameters in Ar and He plasmas

Experimental measurements of the hollow cathode DC glow discharge parameters in Ar and He plasmas

Key Features in the Operation of KSTAR

Initial phase wall conditioning in KSTAR

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