Speaker
Mervi Mantsinen
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1072.pdf
Modelling of ICRF heating in ASDEX Upgrade discharges with
pure wave heating relevant to the ITER baseline scenario
M.J. Mantsinen1,2, V. Bobkov3, D. Gallart1, T. Pütterich3, O. Sauter4,
the EUROfusion MST1 Team* and the ASDEX Upgrade Team
1
Barcelona Supercomputing Center, Barcelona, Spain
2
ICREA, Barcelona, Spain
3
Max-Planck-Institut fur Plasmaphysik, Garching, Germany
4
Swiss Plasma Center, EPFL-SPC, Switzerland
*See the author list of H. Meyer et al. 2017 Nuclear Fusion 57 102014.
The baseline or reference scenario is one of the basic operational scenarios foreseen for
ITER. It is envisaged to deliver fusion power of 500 MW and fusion gain Q10 using ELMy
H-mode discharges at Ip =15 MA, BT = 5.3 T, normalized plasma pressure N = 1.8 and
normalized confinement H98y2 = 1 with a safety factor q95 = 3. Experiments on present-day
devices provide important insights in preparing ITER operation. This paper focuses on
modelling of ICRF heating in ASDEX Upgrade (AUG) plasmas with pure wave heating, i.e.
ICRF and ECRF heating. These discharges are of interest because they approach the
conditions of burning ITER baseline plasmas with predominant electron heating by
fusion-born alpha particles and small externally applied torque. The discharges were carried
out at Ip = 0.9-1.15 MA, BT = 1.8-1.85 T with q95 = 3 and 3.6. Up to 3.9 MW of ICRF power
was applied with a frequency of 30 MHz tuned to a H minority ion resonance at r/a 0.2-0.3
on the high-field side. Up to 3.4 MW of ECRF power was applied using 140 GHz in X3
mode. Stable discharges with N = 1.2-1.7 and H98y2 = 0.75-1.1 were obtained. We have
modelled the discharges using the ICRF modelling code PION. Considering nH/(nH+nD) =
5% which is typical in AUG plasmas and the full ICRF toroidal mode number spectrum, we
find that H minority heating dominates, absorbing 55-70 % of PICRF, while direct electron
damping and 2nd harmonic D damping are about 25-40 % and 5-10 %, respectively. Due to
the off-axis ICRF resonance, the average energy of ICRF-accelerated ions is relatively low,
and they heat prominently bulk ions in collisions. The total ICRF electron heating is limited
to about 40% of PICRF. We find that the electron heating fraction by ICRF could be improved
(1) by operating at 1.95T which moves the ICRF resonance to the plasma center or (2) using
55 MHz which places the 2nd harmonic H resonance in the plasma center. The latter provides
an energetic H minority tail that favours strong electron heating (up 70% of of PICRF) with a
central power deposition and a similar single-pass damping as H minority heating.
