The Science Program of the TCV Tokamak: Exploring Fusion Reactor and Power Plant Concepts
S. Coda, (E. Schuster), et al. (Collaboration Paper)
IAEA Fusion Energy Conference
Saint Petersburg, Russia, October 13-18, 2014
Abstract
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TCV is acquiring a new 1 MW neutral beam and 2 MW additional
third-harmonic ECRH to expand its operational range. Its existing
shaping and ECRH launching versatility was amply exploited in an
eclectic 2013 campaign. A new sub-ms real-time equilibrium
reconstruction code was used in ECRH control of NTMs and in a prototype
shape controller. The detection of visible light from the plasma
boundary was also successfully used in a position-control algorithm.
A new bang-bang controller improved stability against vertical
displacements. The raptor real-time transport simulator was employed
to control the current density profile using ECCD. Shot-by-shot
internal inductance optimization was demonstrated by iterative
learning control of the current reference trace. Systematic studies of
suprathermal electrons and ions in the presence of ECRH were performed.
The L–H threshold power was measured to be ∼50–75% higher in both H
and He than D, to increase with the length of the outer separatrix,
and to be independent of the current ramp rate. Core turbulence was
found to decrease from positive to negative edge triangularity deep
into the core. The geodesic-acoustic mode was studied with multiple
diagnostics, and its axisymmetry was confirmed by a full toroidal
mapping of its magnetic component. A new theory predicting a toroidal
rotation component at the plasma edge, driven by inhomogeneous
transport and geodesic curvature, was tested successfully. A new
high-confinement mode (IN-mode) was found with an edge barrier in
density but not in temperature. The edge gradients were found to
govern the scaling of confinement with current, power, density, and
triangularity. The dynamical interplay of confinement and MHD modes
leading to the density limit in TCV was documented. The heat flux
profile decay lengths and heat load profile on the wall were documented
in limited plasmas. In the snowflake (SF) divertor configuration the
heat flux profiles were documented on all four strike points. SF
simulations with the emc3-eirene code, including the physics of the
secondary separatrix, underestimate the flux to the secondary strike
points, possibly resulting from steady-state E × B drifts. With neon
injection, radiation in a SF was 15% higher than in a conventional
divertor. The novel triple-null and X–divertor configurations were also
achieved in TCV.