Speaker
Daria Ricci
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1074.pdf
Discharge recovery by means of EC assisted start-up
D. Ricci1, G. Granucci1, S. Coda3, D. Farina1, F. Figini1, S. Garavaglia1, C. Galperti3, F.
Maviglia2, A. Moro1, J. Sinha3, the TCV team*, and the MST1 team**
1
IFP-CNR, Milan, Italy
2
EUROfusion Consortium, Garching, Germany
3
Swiss Plasma Center, EPFL, CH-1015 Lausanne, Switzerland
In view of an efficient pulsed operation scenario of future nuclear fusion reactors, the
effectiveness of a prompt and reliable plasma start-up is essential to improve plasma
performance and reproducibility, especially after a disruptive event, as well as to reduce dwell
time between pulses. The foreseen solution to widen the operational window with respect to
the pre-pulse conditions (background pressure and impurity content) is the use of Electron
Cyclotron (EC) additional heating, which can compensate for radiation losses and sustain the
plasma burn-trough phase.
In order to design the operational scenario of future demonstration reactors (DEMO) it is
mandatory to set appropriate codes capable of extrapolating from present experiments to
future scenarios. Experiments on the TCV tokamak focused on discharge recovery by means
of EC assisted start-up (82.7 GHz, XM2) have been carried out with toroidal electric field of
0.7 V/m, pressure before startup ranging between 2 and 10 mPa and neutral composition
dominated by Ar impurity. In the deuterium-dominated plasma, the use of EC makes start-up
effective even at reduced pumping speed (to mimic the DEMO dwell phase) assuming enough
power (>400KW). As expected, on this background, adding Ar as impurity leads to an
increased power threshold for a sustained startup. Experimental results have been reproduced
successfully with simulations provided by BKD0 code, which models in detail the burn-
though phase and includes a consistent calculation of the EC absorbed power computed by the
beam-tracing code GRAY in low density plasma and with a realistic description of the beam
injection conditions, including polarization mix after beam reflection at the inner wall. The
required additional power and impurity impact on startup have been determined for TCV and
extrapolated to ITER, JT-60SA and DEMO.
*
See the author list of ’S. Coda et al 2017 Nucl. Fusion 57 102011’
**
See the author list of ‘H. Meyer et al., Nucl. Fusion 57, 102014 (2017)’
