An imaging hea y ion beam p obe diagnos ic o he ASDEX Upg ade
okamak
J.Galdon-Qui oga1, G.Bi kenmeie 1,2, V.Ole skaia1,2, M.Socho 1, G.Anda3, K.Bald1,
M.Dunne1, M.Ga cia-Munoz4, A.He mann1, K.Kaune 1, D.Nagy3, J.F.Ri e o-Rod iguez4,
M.Rod iguez-Ramos 4, V.Rohde1, E.S umbe ge 1, J.J. Toledo 4, E.Viezze 4,
E.Wol um1, S.Zole nik3, U.S o h1,2and he ASDEX Upg ade4Team
1Max Planck Ins i u e o Plasma Physics, Ga ching, Ge many
2Physics Depa men E28, Technical Uni e si y o Munich, Ga ching, Ge many
3Wigne RCP, EURATOM Associa ion HAS, Budapes , Hunga y
4Cen o Nacional de Acele ado es (CNA), Uni e si y o Se ille, Spain
In oduc ion
A new diagnos ic - he imaging hea y ion beam p obe (i-HIBP) [1, 2] - o he simul aneous
measu emen o plasma po en ial, magne ic ield and densi y luc ua ions is being de eloped
a he ASDEX Upg ade (AUG) okamak. The diagnos ic uses an ion beam in o de o ex ac
in o ma ion o he plasma as in classical hea y ion beam p obes (HIBP) [3], bu uses an injec o
echnology simila o hose o beam emission spec oscopy (BES) diagnos ics and a scin illa o
pla e as pa icle de ec o like in as -ion loss de ec o s (FILD) [4]. The measu emen p inci-
ple is illus a ed in Fig.1 o e e ence [1]. A neu al beam o hea y a oms (Cs in his case) is
launched in o he plasma wi h an ene gy o 70 keV. As his neu al p ima y beam pene a es he
plasma, i is ionized leading o he gene a ion o a an o cha ged seconda y beams which a e
de lec ed by he okamak magne ic ield. The an o seconda y beams is collec ed by a scin il-
la o pla e placed behind he limi e shadow o he machine. The selec ed scin illa o ma e ial
is he so called TG-G een (S Ga2S4:Eu2+), widely used in o he diagnos ics such as FILDs.
The ligh pa e n emi ed by he scin illa o , which is imaged by a as came a, con ains adially
esol ed in o ma ion abou he densi y, po en ial and magne ic ield in he edge and sc ape-o
laye egions o he plasma. The use o a neu al p ima y beam allows o educe he p obing
beam ene gy compa ed o s anda d HIBPs, while he use o an in- essel scin illa o as de ec ion
sys em makes he sys em mo e compac and imp o es he adial esolu ion o he sys em.
The plasma densi y can be eco e ed om he in ensi y measu emen , while displacemen s
o he ligh pa e n - in he ollowing s ike-pa e n - p o ide in o ma ion abou plasma po en-
ial and magne ic ield luc ua ions. Magne ic ield luc ua ions, such as hose expec ed due o
changes in he cu en densi y p o ile, lead o a shi o he whole s ike-pa e n, while luc u-
a ions o he plasma po en ial lead o local shi s o he s ike-pa e n. This way he displace-
46 h EPS Con e ence on Plasma Physics P1.1017
men s due o magne ic ield and po en ial pe u ba ions can be disc imina ed. The di e ence in
he ime-scales o he phenomena o be in es iga ed can also be used o disc imina ion.
Beam modelling
The ajec o ies o he seconda y beams ha e been calcula ed wi h he ull-o bi ollowing
code FIOS [1], which can handle 3D elec ic and magne ic ields. I was ound ha he o oidal
ield ipple should be included in he simula ions since i can lead o a shi o he s ike-pa e n
o up o ∼3.5 cm, i an unapp op ia e o oidal injec ion posi ion ela i e o he o oidal ield
coils is selec ed. In o de o calcula e he signal in ensi y a he scin illa o pla e, a model o he
beam a enua ion has been implemen ed which akes in o accoun elec on impac ioniza ion
and cha ge exchange eac ions. The model is desc ibed in e e ences [1] and [2]. I is ound
ha he seconda y ion cu en densi y eaching he scin illa o s ongly depends on he plasma
densi y p o ile. Fo a scena io wi h a co e line a e aged densi y o ¯ne=2.6·1019 m−3, a cu en
densi y o he o de o ∼mA/m2is expec ed a he scin illa o pla e, while o a scena io wi h
¯ne=7.8·1019 m−3, he cu en densi y expec ed a he scin illa o pla e is educed o ∼nA/m2.
A numbe o simula ions ha e been ca ied ou o ob ain he op imal pa ame e s o he beam
injec ion and de ec ion geome y. The op imiza ion p ocess aimed a achie ing maximum signal
le el a he scin illa o pla e as well as maximum s ike-pa e n displacemen s due o magne ic
ield and po en ial pe u ba ions. A he same ime, he op imiza ion p ocess was cons ained by
space limi a ions, po a ailabili y and compa ibili y wi h cu en ly exis ing diagnos ics in he
same sec o . The inal injec ion pa ame e s a e o a baseline scena io wi h a plasma cu en Ip
and magne ic ield B o I p/B =0.8MA/2.5Ta e: o oidal injec ion angle θ o =5o; poloidal
injec ion angle θpol =0o, injec ion ene gy E0=70 keV. The adial co e age o he diagnos ic
is expec ed o be om ρpol >0.85.
The expec ed ange o ope a ion o he diagnos ic is expec ed o be wide enough o co e
all he possible scena ios in o wa d ield con igu a ion. This is illus a ed in Fig.1. In o de
o es ima e his ope a ional ange, we assume ha he injec ion ene gy o he beam should be
changed o di e en B in o de o keep he same e ec i e La mo adius o he seconda y
beams. The e o e, he injec ion ene gy has o be scaled as Eb= ( B
B0)2·E0, whe e he subindex 0
e e s o he baseline se up. On he o he hand, we assume ha a ia ions o he plasma cu en
lead o a global displacemen o he s ike-line o 1 cm / 100 kA, as in e ed om he simu-
la ions discussed abo e. The alidi y o his es ima ion has been assessed by he s ike-pa e n
calcula ion a speci ic scena ios, indica ed by he colo ed diamonds in Fig.1, spanning di e en
B and Ip alues. The beam ene gy was scaled acco dingly as desc ibed p e iously. In all cases
he s ike-pa e n was ound o lay wi hin he scin illa o limi s.
46 h EPS Con e ence on Plasma Physics P1.1017
Figu e 1: Es ima ed op-
e a ional ange o he i-
HIBP diagnos ic a AUG.
The con ou lines indica e
he injec ion ene gy o he
beam. The shaded egion
indica es he ope a ional
space accesible o he di-
agnos ic, wi hou aking
in o accoun he beam de-
lec ion pla es.
A sensi i i y s udy has been ca ied ou o de e mine which
physics phenomena can be in es iga ed wi h he i-HIBP a AUG
[5]. To his end, he displacemen o he s ike-pa e n on he scin-
illa o pla e due o magne ic ield and plasma po en ial luc ua ions
has been e alua ed o di e en phenomena such as: cu en den-
si y e olu ion du ing an edge localized mode (ELM) cycle, applica-
ion o ex e nally applied magne ic pe u ba ions (MP) o geodesic
acous ic modes (GAMs) among o he s. The expec ed s ike-pa e n
displacemen s and sensi i i y a e in ag eemen wi h hose desc ibed
in [1], anging om ∼0.2mm local shi s due o po en ial pe u ba-
ions up o ∼3mm global shi s due o magne ic ield pe u ba ions.
Ha dwa e a angemen : ou essel
The main ou - essel componen o he diagnos ic is he beam
injec o . The injec o will be placed in sec o 13 o AUG, whe e
he injec ion is done h ough a po loca ed sligh ly abo e he mid-
plane. The injec o is o ien ed 5o o oidally owa ds sec o 14, ac-
co dingly o he baseline injec ion pa ame e s ound in he p e i-
ous sec ion. The injec o is based on he design desc ibed in [6]
and has been p o ided by he Wigne Ins i u e. The main elemen s
a e: a high- ol age cage ha con ains he ion sou ce, he emi e
(∼70kV) and ex ac o (∼60kV ) elec odes; an elec on supp es-
sion ing (∼ −0.5kV ); a pai o de lec ion pla es o beam poloidal
and o oidal s ee ing (±0.5kV ), as well as o as beam chopping
(up o 250 kHz); a neu alize chambe ; and a diagnos ic chambe ,
which con ains a Fa aday cup and 2 came as o beam moni o ing, and which has been e-
designed o include a se o collima o s o educe he size o he beam. An addi ional Fa aday
cup can be placed be ween he de lec ion pla es and he neu alize , and a mi o can be placed
be ween he HV box and he de lec ion pla es o obse a ion o he ion sou ce.
Ha dwa e a angemen : in essel
The main in- essel componen s o he diagnos ic a e an op ical head and an image guide.
The op ical head, shown in Fig.2 con ains he scin illa o pla e (16.9 cm heigh x 6 cm wid h)
o he measu emen o he seconda y beams, a he mocouple o moni o he empe a u e o he
pla e, a cu en measu emen and a lamp. The op ical head is p o ec ed by a ile on he plasma
acing side, which is 2.5 cm behind he shadow o he limi e su ace. The op ical head has an
46 h EPS Con e ence on Plasma Physics P1.1017
Figu e 2: (a) Op ical head o he i-HIBP diagnos ic. (b) Pic u e o he scin illa o powde de-
posi ed on he s ainless s eel pla e.
opening o app oxima ely ∼5x15 cm in he op side, in o de o allow he seconda y beam
ajec o ies in o he scin illa o . A shu e ha closes his opening is also ins alled o a oid he
coa ing o he scin illa o du ing bo oniza ions. The ligh emi ed by he scin illa o is imaged
by an objec i e consis ing o 6 lenses which p ojec s he image o he scin illa o on o a 1.8 m
long SCHOTT image guide, consis ing o 1700x700 glass ibe s, which is hen imaged om
ou side he acuum window wi h a high speed came a.
Summa y
An imaging hea y ion beam p obe has been designed and will be ins alled in he AUG oka-
mak. Modelling o he beam ajec o ies has been ca ied ou wi h a ull o bi ollowing code
which can handle 3D magne ic and elec ic ields, while he a enua ion o he beam is calcu-
la ed aking in o accoun elec on impac ioniza ion and cha ge exchange eac ions. Based on
hese simula ions, he injec ion and de ec ion geome ies ha e been op imized while espec ing
he spa ial es ic ions, and he in- and ou - essel componen s ha e been designed acco dingly.
Labo a o y expe imen s a e cu en ly ongoing o cha ac e ize he beam and he scin illa o e-
sponse o Cs i adia ion, while he manu ac u ing o all componen s o he diagnos ic is being
inalized. The i-HIBP a AUG is o eseen o go in ope a ion by he end o 2019.
Re e ences
[1] J.Galdon-Qui oga, Jou nal o Ins . 12, C08023 (2017)
[2] G.Bi kenmeie e al, Jou nal o Ins . (submi ed)
[3] A.V. Melniko e al, Nucl. Fusion 57, 072004 (2017)
[4] M.Ga cia-Munoz e al, Re . Sci. Ins um. 80, 053503 (2009)
[5] V.Ole skaia e al, DPG Con e ence (2019)
[6] G.Anda e al, Re . Sci. Ins um. 89, 013503 (2018)
46 h EPS Con e ence on Plasma Physics P1.1017