Contributo in atti di convegno, 2018, ENG

PHYSICS RESEARCH ON THE TCV TOKAMAK FACILITY: FROM CONVENTIONAL TO ALTERNATIVE SCENARIOS AND BEYOND

S. Coda et alt.

S. CODA for the TCV team1 and the EUROfusion MST1 team2 Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center, CH-1015 Lausanne, Switzerland (e Istituto di Fisica del Plasma CNR, Milano - Italia -)

The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device's unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with ECRH was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1-MW NBI has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and stationary non-inductive discharges sustained by ECCD and NBCD. In H-mode, the pedestal pressure and plasma stored energy are insensitive to fueling, whereas nitrogen seeding moves the pedestal outwards and increases the stored energy. High fueling at high triangularity is key to accessing the attractive small-ELM (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The GAM, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, SOL transport, and turbulence were studied in L- and H-mode in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power "starvation" reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in H-mode is obtained with impurity seeding and is insensitive to divertor geometry. In the attached L-mode phase, increasing the outer connection length reduces the in-out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable-configuration baffles and cryo-pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5-MW ECRH and 1-MW NBI heating will be added.

27th Fusion Energy Conference, Ahmedabad, India, 2018

Keywords

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CNR authors

Mantica Paola

CNR institutes

IFP – Istituto di fisica del plasma "Piero Caldirola"