WEST actively cooled load resilient ion cyclotron resonance heating system results

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WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m−2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described.

Section: Rf Heated Plasmas and W Contaminationmentioning

confidence: 99%

“…The PFCs are all tungsten and actively cooled [1]. WEST is designed to operate in steady-state long pulses up to 1000 s [2] (figure 1) with high particle fluence, thanks to its continuous wave (CW) radiofrequency (RF) heating and current drive systems: ion cyclotron resonance heating (ICRH) [3,4] and lower hybrid current drive (LHCD) [5].…”

Section: Introductionmentioning

confidence: 99%

Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation

Bucalossi

2022

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“…For two-strap arrays, the wave-SOL interaction is minimized with balanced strap power and [0π] phasing. In WEST, the phasing δϕ between left and right RF voltages on the matching capacitors (see figure 1) is controlled in real time [84]. Figure 7 plots the WI line brightness in two antenna side limiters and in a nearby passive limiter over a dynamic δϕ scan.…”

Section: Two-strap Antennas: Effect Of Strap Phasing and Power Sharin...mentioning

confidence: 99%

The geometry of the ICRF-induced wave–SOL interaction. A multi-machine experimental review in view of the ITER operation

Colas¹,

Urbanczyk²,

Goniche³

et al. 2021

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As part of ITPA-Integrated Operational Scenario activities, this contribution reviews recent experimental characterizations of radio-frequency (RF)-induced scrape-off layer (SOL) modifications of various tokamaks worldwide and of the LArge Plasma Device at UCLA. The phenomenology, as observed using a large variety of measurement techniques, is consistent with expectations from RF sheath rectification. Emphasis is then put on the complex three-dimensional (3D) spatial patterns of the RF–SOL interaction, in relation to the magnetic topology and the spatial distribution of RF currents over the metallic structures surrounding the RF wave launchers. Dependence on the local plasma parameters in the antenna vicinity is also briefly addressed. The final part discusses implications for future devices.

“…All antennas are actively-cooled and equipped by tungsten-coated guard limiters. In the 2019 and 2020-21 campaigns, the LHCD and ICRH coupled powers have both reached ~5MW/1s separately (up to 5.3MW/4s for LHCD) and 8.8MW/0.5s when combining the two RF systems [2,3]. Long pulse operation was Topic: EX also carried out with LHCD (PLH=3.0MW) extending the pulse length to 55 seconds .The experiments were performed at high magnetic field (Bt=3.6-3.7T) in a large range of plasma configurations: X-point plasmas (R~2.5m, a~0.45m,~1.3) in LSN and USN configuration, plasma current in the 0.3-0.7MA range (q95~3-6), line-averaged electron density in the 2.5-8.5×10 19 m -3 range (ne/nGW=0.3-0.8).…”

Section: Introductionmentioning

confidence: 99%

Developing high performance RF heating scenarios on the WEST tokamak

Goniche

Ostuni²,

Bourdelle³

et al. 2022

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High power experiments, up to 9.2 MW with LHCD and ICRH, have been carried out in the full tungsten tokamak WEST. Quasi non inductive discharges have been achieved allowing to extend the plasma duration to 53s with stationary conditions in particular with respect to tungsten contamination. Transitions in H mode are obtained lasting up to 4s with weak energy increment at the power crossing the separatrix is close to the threshold. Hot L mode plasmas (Te(0)>3keV) with a confinement time following the ITER L96 scaling are routinely obtained. The weak aspect ratio dependence of this scaling law is confirmed. Tungsten accumulation is generally not an operational issue on WEST. Difficulty of burning through tungsten can prevent from accessing to a hot core plasma in the ramp-up phase or can lead to rapid collapse of the central temperature when radiation is enhanced by a slight decrease of the temperature. Apart few pulses post-boronization, the plasma radiation is rather high (Prad/Ptot~50%) and is dominated by tungsten. This fraction does not vary as the RF power is ramped up and is quite similar in ICRH and/or LHCD heated plasmas. An estimate of the contribution of the RF antennas to the plasma contamination in tungsten is given