Wall conditioning in JT-60

Arai, Takashi; Yamamoto, Masahiro; Akino, N.; Kodama, K.; Nakamura, Hiroo; Niikura, S.; Takatsu, H.; Shimizu, Masatsugu; Ohkubo, M.; Ohta, M.

doi:10.1016/0022-3115(87)90424-7

Cited by 8 publications

(4 citation statements)

References 2 publications

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“…Figure 5 shows the magnetic flux patterns (top figures), as reconstructed from the values of the currents in the sixteen shaping coils of TCV, and the ion saturation currents (bottom) for different combinations of B H and B V in ECWC discharges at B T = 1.3 T, p = 10 −2 Pa, P EC = 480 kW. The different plots in figure 5 are labelled B V + B H , B V + 2B H and 3 2 B V + 3B H , where B V ~ 0.6%B T and B H ~ 0.1%B T in the equatorial plane. Starting from the pure vertical case, the radial component of the poloidal field was gradually increased using the shaping coils in the equatorial plane, bending there the vertical magnetic flux lines in and outboard, resulting in 'barrel-shaped' patterns.…”

Section: Discharge Homogeneity and Wall Coveragementioning

confidence: 99%

“…Following this and the execution of the last fourteen He-ECWC discharges, an ohmic D 2 -plasma could be successfully sustained (refered as 'sb'), whereas it would not have been possible without conditioning. The last six He-ECWC discharges with optimized combinations of vertical and horizontal magnetic fields, such as those labelled B V + 2B H and 3 2 B V + 3B H in figure 5, allowed recovering 75% (0.45 Pa • m 3 ) of the fuel in the second session. Moreover, gas balance indicated that 4% of the He injected was on the average retained in the carbon walls in these shots.…”

Section: Efficiency Of Ecwcmentioning

confidence: 99%

“…In the presence of such a magnetic field, conventional DC-glow discharges are unstable and can therefore no longer be used between plasma pulses. Compatible with the magnetic field, Taylor discharge cleaning (TDC) has been developed and routinely used with B T on between plasmas in JT-60U to recover a satisfactory wall pumping capacity or low impurity levels, for instance after a disruption [3,4]. These short low current plasmas, typically with duration of 20-40 ms and a current of a few tens of kA, are created inductively in the vacuum vessel by rapidly changing the currents in the central solenoid coil, at a repetition rate of ~0.2-1 Hz.…”

Section: Introductionmentioning

confidence: 99%

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Development of helium electron cyclotron wall conditioning on TCV

et al. 2017

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JT-60SA envisions electron cyclotron wall conditioning (ECWC), as wall conditioning method in the presence of the toroidal field to control fuel and impurity recycling and to improve plasma performance and reproducibility. This paper reports on Helium ECWC experiments on TCV in support of JT-60SA operation. Nearly sixty Helium conditioning discharges have been successfully produced in TCV, at a toroidal field B T = 1.3 or 1.54 T, with gyrotrons at 82.7 GHz in X2 mode, mimicking ECWC operation in JT-60SA at the second harmonic of the EC wave. Discharge parameters were tuned in order to (i) minimize the time for the onset of ECWC plasmas, thus minimizing absorption of stray radiation by in-vessel components, (ii) improve discharge homogeneity by extending the discharge vertically and radially, and wall coverage, in particular of inboard surfaces where JT-60SA plasmas will be initiated, (iii) assess the efficiency of He-ECWC to deplete carbon walls from fuel. An optimized combination of vertical and radial magnetic fields, with amplitudes typically 0.1 to 0.6% of that of B T , has been determined, which resulted in lowest breakdown time, improved wall coverage and enhanced fuel removal. A standard ohmic D 2 -plasma could be then sustained, whereas it would not have been possible without He-ECWC.

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Section: Discharge Homogeneity and Wall Coveragementioning

confidence: 99%

Section: Efficiency Of Ecwcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development of helium electron cyclotron wall conditioning on TCV

et al. 2017

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“…A wide range of the target plasma densities has been achieved with this divertor configuration. Before high power plasma operation, extensive Taylor type discharge conditioning is performed to reduce the impurity influx from the TiC coated Mo limiter and from the TiC coated INCONEL first wall [18]. The plasma is initiated in a limiter discharge, and the divertor configuration is formed after about 200 ms.…”

Section: Experimental Conditions and Diagnosticsmentioning

confidence: 99%

Incremental energy confinement time during H⁰beam heating in JT-60

Kikuchi¹,

Hirayama²,

Shimizu³

et al. 1987

Nucl. Fusion

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Characteristics are presented of the energy confinement time resulting from neutral hydrogen beam heating of JT-60 tokamak plasmas with a plasma current, Ip, of 1-2 MA, a line averaged electron density, n e , of 1.5-7 X 10 19 m~3 and an absorbed beam power, P a b S , up to 20 MW. The plasma energy content follows an offset linear relation to the absorbed power. The incremental energy confinement time for thermal components, rg c , is almost independent of I p and n e at 60 ms, while the incremental energy confinement time for the total plasma energy, TJJ<£, decreases with plasma density. The value of rg c in JT-60 coincides with the prediction of the Shimomura-Odajima scaling of L-mode discharges.

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