Speaker
Antti Salmi
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1068.pdf
Particle sources and SOL dynamics in JET strike point sweeping experiments
A. Salmi1, Tala1, A. Järvinen2, D. Dunai3, R. Gomes4, P. Lomas5, L. Meneses4,6, S. Mordijck7,
V. Naulin8, J. Juul Rasmussen8, M. Romanelli4, A.C.C. Sips9,10, and JET contributors*
Eurofusion Consortium JET, Culham Science Centre, Abingdon, OX14 3DB, UK
1
VTT, Espoo, Finland; 2LLNL, Livermore, USA; 3Wigner Research Centre for Physics, Budapest, Hungary;
4
IPFN, IST, Universidade de Lisboa, Portugal; 5CCFE, Abingdon, UK; 6ITER Organization, France; 7College
of William & Mary, Virginia, USA; 8DTU Physics, Lyngby, Denmark; 9JET Exploitation Unit, Culham, UK;
11
European Commission, Brussels, Belgium;
JET experiments to study plasma fuelling, edge transport and scrape-off-layer (SOL) behaviour
have been performed for the first time using a technique based on strike point sweeping. Sweeping
itself is routinely used in JET high power discharges to, e.g., spread the heat flux or to measure
high radial resolution SOL profiles with Langmuir probes. Here, however, we employ this
technique at the highest feasible frequencies (limited by machine safety) to study its feasibility
for edge plasma fuelling studies to complement gas puff
modulations [1, 2].
The sweep modulations are performed in various strike
point configurations and in plasmas with Ohmic and L/H-mode
confinement and in two isotopes H/D. By comparing the core and
SOL electron density measurements, line radiation across the Figure 1 Strike point sweeping
poloidal plane and divertor Langmuir probe data we can observe: perturbs the recycled particle
fluxes in the vicinity of the strike
(1) periodic LH transitions facilitated by the strike point movement points as well as the divertor
from horizontal to vertical target and back in < conditions in general thus
affecting upstream SOL profiles
2 conditions, (2) frequency independent (4/8/18.5Hz) midplane and core fuelling. The main
SOL electron density changes (3) radial SOL ‘communication plasma shape as well as other
heating and fuelling parameters
times’ of the order of 10-20 ms (4) parallel SOL communication are kept constant.
times within measurement accuracy (<5ms). Present observations seem to suggest that sweeping
is not generating significant modulated neutral particle sources inside the separatrix but that the
effect at the pedestal comes via SOL density modulation as a boundary condition.
EDGE2D/EIRENE [3,4] modelling is underway to identify the dominant physics
mechanisms (pumping, recycling, flux expansion etc) responsible for these observations and to
develop this experimental technique for plasma fuelling studies.
[1] A. Salmi et al. EPS, Belfast, Ireland, 2017 [3] R Simonini et al., CPP, 34 (1994) (368-373).
[2] T. Tala et al. IAEA FEC, Ahmedabad, India, 2018 [4] D. Reiter et al. FS&T, 74 (2005) (172-186).
*
See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001ʺ
