Speaker
Lucía Sanchis-Sanchez
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I5.120.pdf
Fast-Ion Edge Resonant Transport Layer Induced by Externally
Applied 3D Fields in the ASDEX Upgrade Tokamak
L. Sanchis1*, M. Garcia-Munoz1, A. Snicker2, J. Galdon-Quiroga1, D. A. Ryan3,
M. Nocente4, J. F. Rivero-Rodriguez1, L. Chen5, F. Zonca5,6,W. Suttrop7, E. Viezzer1,
M. A. Van Zeeland8, D. Zarzoso9, ASDEX Upgrade and EUROfusion MST1§ Teams
1
Dept. of Atomic, Molecular and Nuclear Physics, Universidad de Sevilla, 41012, Spain; 2Dept.
of Applied Physics, Aalto University, FI- 00076, Aalto, Finland; 3CCFE, Culham Science
Centre, OX14 3DB, Abingdon, UK; 4Universita degli Studi di Milano-Bicocca, Piazza della
Scienza 3, 20126, Milano, Italy; 5IFTS, Zhejiang University, 310027, Hangzhou, China; 6ENEA
C. R,. 65-00044, Frascati, Italy; 7Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2,
85748, Garching, Germany; 8General Atomics, CA 92186-5608, San Diego, USA; 9Laboratoire
PIIM, Aix-Marseille Université, France
*Email: lsanchis@us.es
Externally applied 3D fields are routinely used in present tokamaks to mitigate or even
suppress ELMs [1]. Symmetry breaking 3D fields can, however, cause significant fast-
ion losses threatening the integrity of future large devices. The impact of externally
applied 3D fields on the ELM stability depends strongly on the poloidal spectra of the
applied perturbative fields [2]. Recent experiments in the ASDEX Upgrade tokamak
have revealed the existence of an Edge Resonant Transport Layer (ERTL) responsible
for the fast-ion losses observed in the presence of externally applied 3D fields. The
amplitude and velocity-space distribution of the measured fast-ion losses depends on the
3D field poloidal spectrum, the magnetic background helicity (q95) and the plasma
collisionality.
100
Full orbit simulations carried out with the ωpol/ωtor ERTL
1.11
1.2
1.37
1.425
90 2
1.55
2.25
1.6
ASCOT code using the plasma response 2
80
calculated with MARS-F reproduce a strong 1
(a.u.)
70
correlation of fast-ion losses with the 3D fields’
E (keV)
1.11
1.425
1.37
60 0
poloidal spectra showing also that toroidal
1.55
1.6
2.25
2
50
sideband harmonics can modify significantly the −1
40
overall fast-ion losses. The plasma response can
1.711
30 ASCOT
reduce or amplify the resonant fast-ion transport. −2
1.
1.3
2.25
1.55
#33143 Δφ =40º UL Separatrix
Externally applied 3D fields induce a variation in 1.95 2 2.05 2.1 2.15
the particle toroidal canonical momentum (δPφ) Fig 1. structuresRin(m) the presence of a Δϕ =40º UL
that is maximized around the separatrix due to magnetic perturbation configuration overlapped with
the overlapping of a large number of linear and matching orbital resonances (ω /ω ). Black-blue
pol tor
areas represent outwards transport while yellow-white
nonlinear resonances between the perturbative means inwards transport.
fields and the particle orbital frequencies. Figure 1 shows the fast-ion as a
function of particle energy and initial position in the presence of an externally applied
3D field caused by the ELM mitigation coils in AUG with a differential phase between
the upper and the lower set of coils of ΔϕUL=40º. The fast-ion ERTL depends strongly
on the particle pitch-angle, but not significantly on the particle energy suggesting that
similar resonances may also exist for thermal ions and thus shedding some light on the
physics underlying the thermal density pump-out commonly observed with externally
applied 3D fields. The implications of the results presented here for the fast-ion
confinement in ITER with externally applied 3D fields will be discussed.
[1] T. E. Evans et al, Nature Physics, 2 419 (2006)
[2] R. Nazikian et al, Physical Review Letters, 114 105002 (2015)
§ H.Meyer et al, Nucl. Fusion 57 102014 (2017)
