Speaker
Matteo Vallar
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1068.pdf
Nonlinear contribution of neutral beam injection in TCV EC-heated
advanced tokamak scenarios
M. Vallar1, M. Agostini1, T. Bolzonella1, S. Coda2, J. Garcia3, B. Geiger4, T. Goodman2, A.
Karpushov2, T. Kurki-Suonio5, C. Piron1, L. Pigatto1, O. Sauter2, N. Vianello1, P. Vincenzi1,
M. Yoshida6 the TCV team and the MST1 team
1. Consorzio RFX, Corso Stati Uniti 4, 35127 Padova, Italy
2. Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-
1015 Lausanne, Switzerland
3. CEA, IRFM, 13108 Saint-Paul-lez-Durance, France
4. Max Planck Institute for Plasma Physics, Garching, Germany
5. Aalto University, P.O. Box 14100, FI-00076 AALTO, Finland
6. National Institutes for Quantum and Radiological Science and Technology, Naka,
Ibaraki 311-0193, Japan
TCV (Tokamak à Configuration Variable) is a tokamak device capable of many different
plasma shapes and positions, equipped with a flexible system of Electron Cyclotron (EC)
antennas and a new Neutral Beam (NB) injector [1]. The auxiliary power from the beam can
reach 1 MW and it is injected tangentially co-current, coupling mostly with ions. This heating
system allows new insights on advanced tokamak scenarios in TCV which, up to now, have
been performed only with EC heating (ECH). These scenarios have high βN, high non-
inductive current fraction and a relevant energetic particle (EP) population fraction (≈10 %).
An internal transport barrier can be generated by reversing the q-profile using EC current-
drive (ECCD) [2]. In this work we show that the effect of the sum of the two heating sources (NBI
and ECH) in TCV high βN plasmas is not linear, and interpretative modelling is carried out to
understand the behaviour of the NB EPs when ECH is present. A statistical study on a set of
experiments with both ECH and NBI is presented to show the effect of NB injection (NBI) on plasma
performance: βN and the plasma stored energy do not increase linearly with NB power. Furthermore,
the contribution to the total plasma current from ohmic transformer, bootstrap current and current
drive are respectively estimated, showing that EC has a strong impact on Zeff, modifying therefore the
plasma resistivity and the ohmic contribution to the current. This effect is taken into account when
applying the Monte Carlo interpretative NBI code NUBEAM. It results that with the combined
application of ECRH and ECCD, the electron temperature and plasma equilibrium change
significantly, impacting on the NB power deposition: CX and orbit losses tend to increase, reducing by
20% the power deposited on plasma species. Modelling suggests that the variation in Te changes the
EP power redistribution among the species, transferring more power to the ions. The impact on EPs
orbit given by ECCD equilibrium modification is performed with the Monte Carlo ASCOT code for
NBI modelling, capable of solving the EP full gyro-motion.
[1] A.N.Karpushov, et al., FED 123 (2017) [2] T P Goodman et al., PPCF 47 (2005)
See the author list "H. Meyer et al 2017 Nucl. Fusion 57 102014"
