Nonlinea elec omagne ic s abiliza ion o ITG mic o u bulence by
ICRF-d i en as ions in ASDEX Upg ade
F.N. de Oli ei a1, H. Doe k2, M.J. Man sinen1, 3, C. Angioni2, R. Bila o2, V. Bobko 2,
M. Dunne2, D. Galla 1, A. Gu ié ez-Milla1, P. Man ica4, T. Ods čil2, G.Ta dini2, X. Sáez1,
he ASDEX Upg ade Team and he EURO usion MST1 Team* 5
1Ba celona Supe compu ing Cen e (BSC), Ba celona, Spain
2Max-Planck-Ins i u ü Plasmaphysik, Ga ching, Ge many
3ICREA, Ba celona, Spain
4Is i u o di Fisica del Plasma “P. Caldi ola”, CNR, Milano, I aly 10
*see he au ho lis o H. Meye e al., O e iew o p og ess in Eu opean Medium Sized Tokamaks owa ds an
in eg a ed plasma-edge/wall solu ion, accep ed o publica ion in Nuclea Fusion.
In oduc ion Elec omagne ic wa es in he ange o Ion Cyclo on Resonance F equencies
(ICRF) ha e many applica ions in usion de ices. While hei use o ex e nal hea ing o 15
magne ically con ined usion plasmas is well es ablished, hei e ec s on he enhancemen
o he plasma con inemen by mic o u bulence s abiliza ion ha e only been ecen ly
disco e ed [1,2]. Fo his e ec a key pa ame e o me i is α=−q2βR∇P/P whe e R is he
okamak majo adius, β is he plasma be a, q is he sa e y ac o and P is he plasma p essu e.
By inc easing a local plasma p essu e g adien and/o be a by ICRF-accele a ed esonan 20
ions, we can dec ease u bulen anspo d i en by mic oins abili ies. We in es iga e he
impac o ICRF-accele a ed as ions in he s abiliza ion o mic o u bulence in wo ASDEX
Upg ade H-mode discha ges [3]. In hese discha ges, in addi ion o 4.5 MW o deu e ium
NBI, 3.5 MW o ICRF powe was applied a a equency o 30 MHz uned o a cen ally
loca ed 3He mino i y esonance. The loca ion o he 3He mino i y esonance was a ied by 25
abou 10 cm by changing he o oidal magne ic ield om 2.8 T in discha ge 31562 o 3 T in
discha ge 31563. The plasma cu en was 0.6 MA and he main ion species was deu e ium.
An inc ease o up o 80% in he cen al ion empe a u e was measu ed, om 3 keV o 5.5
keV, as compa ed o he e e ence discha ge 31555 wi h NBI hea ing only (c. . Fig. 1). The
no malized loga i hmic ion empe a u e g adien , R/LTi, eached a high alue o abou 20, 30
co esponding o a adial g adien o he Ti p o ile o abou 50 keV/m. The 3He ion densi y
is below 5% o he elec on densi y in all discha ges. Thus, he possible e ec o main ion
dilu ion [4] on mic o u bulence s abiliza ion is no expec ed o be signi ican .
Me hodology We use PION [5] and he Fini e Ion D i O bi code FIDO [6] o compu e he
elec omagne ic wa e pa ame e s and he as 3He mino i y ion pa ame e s. Figu e 2 shows 35
44 h EPS Con e ence on Plasma Physics P2.176
he as 3He mino i y ion p essu e p o iles as calcula ed by FIDO. Discha ge 31563 has a
s eepe as 3He ion p essu e p o ile due o a mo e cen al 3He mino i y esonance. Wi h he
as 3He ion densi y, empe a u e, and p essu e p o iles as gi en by FIDO, we e alua e he
loga i hm o he g adien o he as 3He ion densi y and empe a u e which a e used as inpu
pa ame e s in he plasma u bulence code GENE [7]. In his wo k, a s a ic Maxwellian 5
dis ibu ion is assumed o he mal and as 3He ions in GENE. While his can be gene alised
in u u e wo k, we expec ha he obse ed ends ca y o e o a mo e ealis ic dis ibu ion.
pol
Figu e 1: Ion empe a u e Ti p o iles o AUG
discha ges 31562, 31563 and 31555 [3].
Figu e 2: P essu e p o iles o 3He ions o discha ges
31562 and 31563 as calcula ed by FIDO.
Linea esul s Ou linea analyses pe o med wi h GENE show ha elec omagne ic ac i i y
and he sa e y ac o q ha e a s ong impac on he g ow h a e o he Ion Tempe a u e 10
G adien (ITG) ins abili y. This is illus a ed by Fig. 3a which shows he spec al analysis
wi h and wi hou elec omagne ic e ec s, and by Fig. 3b which shows he impac o he sa e y
ac o q on he ins abili y g ow h a e. Sensi i i y analyses wi h espec o q and as 3He ion
pa ame e s such as T , n , R/Ln and R/LT we e ca ied ou o iden i y he pa ame e ange
ha does no include s ong Kine ic Ballooning Mode (KBM) ac i i y. In he elec omagne ic 15
ITG case, he ins abili y g ow h a es dec ease wi h inc easing q, which is opposi e o he
elec os a ic end [8]. We ind ha he ins abili y g ow h a e dec eases wi h inc easing
elec omagne ic ac i i y. Fu he mo e, elec omagne ic ac i i y can inc ease due o he
p esence o as ions, which can lead o a educ ion in he ins abili y g ow h a e.
Nonlinea esul s We ha e ca ied ou non-linea gy okine ic GENE simula ions wi h and 20
wi hou as 3He mino i y ion popula ion. Figu e 4 shows elec ic po en ial luc ua ions wi h
as ions o discha ge 31563. They exhibi cohe en s uc u es known as zonal lows. The
ime-a e aged zonal shea ing inc eases by 25-30% when as ions a e included, sugges ing
44 h EPS Con e ence on Plasma Physics P2.176
an inc ease in he zonal low capabili y o shea he mic o u bulen mode, and he e o e
s abilize i , in he case whe e as ions a e included. Simula ions o longe imes a e on-going
in o de o con i m his esul .
(a)
(b)
Figu e3: (a) Ins abili y g ow h a e γ wi h (g een) and wi hou ( ed) elec omagne ic (EM) ac i i y as gi en
by linea GENE simula ions o discha ge 31563. (b) The dependence o he ins abili y g ow h a e γ on he
sa e y ac o as gi en by linea GENE simula ions o discha ge 31562.
Nonlinea GENE simula ions allow us
o compa e he simula ed hea luxes
wi h hose ob ained by powe balance
analysis o he expe imen . In his
pape we ocus on ion hea anspo
and lea e he ull anspo analysis
including elec ons o a u he s udy.
In discha ge 31563, he expe imen al
in eg a ed ion hea lux is 1.6 MW a
he adial posi ion ρ o = 0.25, deduced
om he modelling o he NBI and
ICRF hea ing wi h he PION, FIDO
and TRANSP codes.
Figu e 4: Elec ic po en ial luc ua ions as gi en by a non-
linea GENE simula ion wi h as ions o discha ge 31563,
showing cohe en s uc u es known as zonal lows. We use
a pe pendicula domain size o 143ρs x 128ρs in x, y o
nonlinea GENE simula ions, wi h a g id o
(256x128x24x32x12) in (x, y, z, //, μ) phase space.
The ion hea luxes as gi en by non-linea GENE simula ions a e shown in Fig. 5 o 5
discha ge 31563 wi h as ions and wi hou as ions. The s a is ical ime-a e aged ion hea
lux is 1.3 and 4.5 MW wi h and wi hou as ions, espec i ely. The o me is much close
o he expe imen al alue o 1.6 MW han he la e . Ou nonlinea simula ions hus con i m
he anspo educ ion in he p esence o as ions.
44 h EPS Con e ence on Plasma Physics P2.176
While i is clea om Fig. 5 ha adding
as ions des abilises elec omagne ic
modes, he exac mechanism by which
ITG u bulence is educed by as ions is
s ill unde in es iga ion. Fo he nonlinea
pa , ou esul s poin owa ds a ela i e
inc ease o zonal low s eng h, which
needs o be con i med by longe
simula ion imes. Fo discha ge 31562,
simila esul s we e ob ained as o
discha ge 31563 in he linea analysis. The
non-linea simula ion o his discha ge is
on-going. I is expec ed o exhibi simila
ea u es as ha o discha ge 31563.
Figu e 5: Ion hea luxes as gi en by non-linea GENE
simula ions o discha ge 31563 wi h as ions and
wi hou as ions. The ed ho izon al line shows he
expe imen al ion hea lux o 1.6 MW. The ime is
exp essed in e ms o GENE no malized uni s, which is
app oxima ely one mic osecond. No quali a i e change
is expec ed o longe simula ion imes ha a e
ongoing.
Conclusions We ha e iden i ied ha he p esence o ICRF-hea ed 3He mino i y ions can
educe ITG g ow h a es in ASDEX Upg ade H-mode plasmas wi h combined NBI and ICRF
hea ing. In nonlinea gy okine ic simula ions wi h he GENE code, he ion hea lux educes
wi h as ions by a ac o o abou ou , eaching a alue close o he expe imen al one. This
wo k can be u he imp o ed by including a mo e ealis ic as ion dis ibu ion unc ion such 5
as a Bi-Maxwellian, which is a ecen new ea u e in GENE [9].
This wo k has been ca ied ou wi hin he amewo k o he EURO usion Conso ium and
has ecei ed unding om he Eu a om esea ch and aining p og amme 2014-2018 unde
he g an ag eemen No 633053. The iews and opinion exp essed he ein do no necessa ily
e lec hose o he Eu opean Commission. We would also like o hank Red Española de 10
Supe compu ación (RES) o he esou ces g an ed, as well as he CINECA esou ces
g an ed h ough he MARCONI-Fusion p ojec .
Re e ences
[1] J. Ci in e al., Phys. Re . Le e s, 111 (2013) 155001. 15
[2] J. Ga cia e al., Nucl. Fusion 55 (2015) 053007.
[3] M.J. Man sinen e al., AIP Con e ence P oceedings, ol. 1689. pp. 030005:1-8, 2015.
[4] G. Ta dini e al., Nucl. Fusion 47 (2007) 280.
[5] L.-G. E iksson and T. Hells en and U. Willén, Nucl. Fusion 33 (1993) 1037.
[6] J. Ca lsson, T. Hells en and L.-G. E iksson, P oc. Join Va enna Lausanne Wo kshop 20
'Theo y o Fusion Plasmas' 1994, p. 351.
[7] F. Jenko, W. Do land, M. Ko schen eu he and B. N. Roge s, Physics o Plasmas 7 (2000)
1904.
[8] F. Jenko, W. Do land and G. W. Hamme , Physics o Plasmas 8, 4096 (2001).
[9] A. Di Siena e al., 2016 J. Phys.: Con . Se . 775 012003. 25
44 h EPS Con e ence on Plasma Physics P2.176
