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S. Coda, M. Agostini, R. Albanese, S. Alberti, E. Alessi, S. Allan, J. Allcock, R. Ambrosino, H. Anand, Y. Andrébe, G. Harrer, EUROfusion MST1 Team, MST1 Team:
"Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond";
Nuclear Fusion, 59 (2019), 11202301 - 11202317.

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 electron-cyclotron resonance heating (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 neutral beam injector has expanded the
parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly noninductive
H-mode discharges sustained by electron cyclotron and neutral beam current drive.
In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling
moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to
either seeding or fueling. High fueling at high triangularity is key to accessing the attractive
small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative
triangularity, consistent with increased confinement and in accord with global gyrokinetic
simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer
transport, and turbulence were studied in L- and H-modes 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 the H-mode is obtained with impurity seeding and has shown little
dependence on flux expansion in standard single-null 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 variableconfiguration
baffles and possibly divertor pumping will be introduced to investigate the effect
of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam
injection heating will be added.

nuclear fusion, tokamak, overview, TCV, MST1, EUROfusion

http://dx.doi.org/10.1088/1741-4326/ab25cb