Hydrogen plasmas with ICRF inverted minority and mode conversion

Transcription

1 Hydrogn plasmas with ICRF invrtd minority and mod convrsion hating rgims in th JET tokamak* M.-L. Mayoral 1, P.U. Lamall, D. Van Estr, E. A. Lrch, P. Baumont 1, E. D La Luna 3, P. D Vris 1, C. Gowrs 1, R. Flton 1, J. Harling 1, V. Kiptily 1, K. Lawson 1, M. Laxåback 4, P. Lomas 1, M.J. Mantsinn 5, F. Mo 6, J.-M. Notrdam 7,8, I. Nuns 9, G. Piazza 1, M. Santala 5 and JET EFDA contributors** 1 Euratom/UKAEA Fusion Association, Culham Scinc Cntr, Abingdon, Oxon, OX14 3DB, U.K. Association Euratom-Blgian Stat, LPP-ERM/KMS, Partnr in TEC, B-1 Brussls, Blgium 3 Asociación Euratom-CIEMAT, Laboratorio Nacional d Fusion, Spain 4 Euratom-VR Association, Swdn 5 Hlsinki U. of Tchnology, Tks-Euratom Association, Finland 6 Association Euratom-RISO, Riso National Laboratory, Dnmark 7 Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Grmany 8 EESA Lab, Univrsity Gnt, Blgium 9 Associação EURATOM/IST, Cntro d Fusão Nuclar, Portugal 1 Forschungszntrum Karlsruh (FZK), Grmany * This papr is an xpandd vrsion of matrial originally prsntd at 16 th Topical Confrnc on Radio- Frquncy in Plasmas, Park City, Utah, April 5. Procdings ditd by Stphn J. Wukitch and P. Bonoli, Amrican Institut of Physics, Mlvill, Nw York, Vol. 787, 1-18, 5 and ** S th Appndix of J. Pamla t al., in Fusion Enrgy 4 (Proc. th Int. Conf. Vilamoura, 4) (Vinna: IAEA) CD-ROM fil OV/1- and PACS numbrs: 5.5.Qt; 5.6.Qt Short titl: ICRF invrtd minority and mod convrsion rgims in JET 1

2 Abstract: During th initial opration of th Intrnational Thrmonuclar Exprimntal Ractor (ITER), it is nvisagd that activation will b minimisd by using hydrogn (H) plasmas whr th rfrnc ion cyclotron rsonanc frquncy (ICRF) hating scnarios rly on minority spcis such as hlium ( 3 H) or dutrium (D). This papr firstly dscribs xprimnts ddicatd to th study of 3 H hating in H plasmas with a squnc of dischargs in which 5 MW of ICRF powr was rliably coupld and th 3 H concntration, controlld in ral-tim, was varid from blow 1 % up to 1 %. Th minority hating rgim was obsrvd at low concntrations (up to %). Enrgtic tails in th 3 H ion distributions wr obsrvd with ffctiv tmpraturs up to 3 kv and bulk lctron tmpraturs up to 6 kv. At around %, a suddn transition was rproducibly obsrvd to th mod convrsion rgim, in which th ICRF fast wav coupls to short wavlngth mods, lading to fficint dirct lctron hating and bulk lctron tmpraturs up to 8 kv. Scondly, xprimnts prformd to study D minority ion hating in H plasmas ar prsntd. This minority hating schm provd much mor difficult sinc modst quantitis of carbon (C) impurity ions, which hav th sam charg to mass ratio as th D ions, ld dirctly to th mod convrsion rgim. Finally, numrical simulations to intrprt ths two sts of xprimnts ar undr way and prliminary rsults ar shown. (Figurs in this articl ar in colour only in th lctronic vrsion)

3 1 Introduction It is nvisagd that, in th initial phas of Intrnational Thrmonuclar Exprimntal Ractor (ITER) [1] opration, H plasmas will b usd to minimis th activation of th machin during th commissioning stags. Th two rlvant ICRF scnarios forsn in H plasmas ar basd on th hating of 3 H minority ions, rfrrd to as ( 3 H)H, or D minority ions, rfrrd to as (D)H. A ky fatur of ths so-calld invrtd scnarios is that th minority ion spcis hav a smallr charg to mass ratio than th majority ion spcis, i.. Z A < Z maj Amaj. min min In th past, tritium (T) invrtd scnarios in D plasmas with T and D fractions of 5 % and 95 % rspctivly, hav bn succssfully tstd during th 1997 JET DT campaign []. Furthr rsults wr also obtaind in th rcnt Trac Tritium Exprimnt (TTE) at JET [3], with tritium concntrations up to around 3.5 %. Nvrthlss, until now ( 3 H)H and (D)H scnarios wr only scarcly documntd. ICRF hating commonly rlis on th propagation of th fast magntosonic wav (in short, fast wav (FW)) to transport nrgy from th plasma dg to th cor. Th FW disprsion rlation in th cold plasma approximation can b writtn as: n [ L n// ][ R n// ] [ S n ] =, // whr R, L and S ar th dilctric tnsor componnts as dfind by Stix [5]; n = k c ω is th rfractiv indx prpndicular to th quilibrium magntic fild, k is th prpndicular wav numbr; n // // = k c ω is th rfractiv indx paralll to th quilibrium magntic fild, k // is th paralll wav numbr. Th FW propagation is illustratd in Figur 1 for plasma with two ion spcis. Two hating scnarios ar shown: an invrtd on ( 3 H)H and a standard on ( 3 H)D. Th FW cut-offs ar found for n // = R and n // = L (rspctivly associatd with th 3

4 right- and lft- handd wav polarisations). Th cold FW rsonanc occurs for n // = S, which corrsponds to th ion-ion hybrid rsonanc layr R ii for a plasma with two ion spcis [6]. Th mod convrsion (MC) rgim occurs if th FW incoming from th low magntic fild sid (LFS) fficintly tunnls through th thin vanscnc layr btwn th lft-hand cut-off and th ion-ion hybrid layr. Thn, considring a finit tmpratur plasma, th FW can b mod convrtd to hot plasma wavs nar th ion-ion hybrid layr. Th natur of ths short wavlngth wavs dpnds on th plasma proprtis [7]. Thy can b kintic Alfvén wavs, ion Brnstin wavs (IBW) or lctromagntic ion cyclotron wavs (ICW), dpnding on th rlativ importanc of tmpratur and poloidal fild ffcts [8][9][1]. Thir main common charactristic is that thy ar strongly dampd by lctron Landau damping (ELD) bcaus of th strong up- or down- shift of k // du to th prsnc of a finit poloidal magntic fild [11]. Th minority hating (MH) rgim occurs whn th FW nrgy is dominantly absorbd at th ion cyclotron rsonanc layr R ic. Th minority ion cyclotron rsonanc condition can b writtn as ω ICRF nω ci k // v// =, whr ω ICRF is th ICRF wav frquncy; ω C is th i minority ion cyclotron frquncy; n is th harmonic numbr and v // is th minority ion paralll vlocity. In this rgim, th FW absorption by th minority ions rsults in th formation of a high-nrgy population, i.. th apparanc of a tail in th minority ion distribution function. Th hating of th background ions and lctrons taks plac on th rathr long tim scal of th minority fast ions collisional slowing-down tim (typically of th ordr of.4 s for th 3 H ions in th xprimnts dscribd in this papr). Whn th nrgy of th fast minority ions is abov a crtain critical nrgy E crit [5], th lctrons ar prdominantly hatd by collisions with th fast ions, whras in th opposit cas mainly ion hating is obtaind. 4

5 In standard scnarios with Z min Amin > maj Amaj Z, th ion-ion hybrid layr R ii is locatd on th high fild sid (HFS) of th minority ion cyclotron rsonanc layr R. In that cas, th FW launchd from th LFS antnnas ncountrs th minority ion cyclotron rsonanc layr first. MH is th main hating scnario unlss th minority concntration xcds a critical valu abov which th fast wav lctric fild componnt E +, which rotats in th sam dirction as th minority ions, is significantly rducd at th minority ion cyclotron layr. In th lattr cas, singl-pass minority ion cyclotron damping dcrass significantly, and a largr fraction of th FW can b mod-convrtd at th ion-ion hybrid layr. In JET, optimal concntration for th MC rgim in D plasmas with 3 H ions was found in th rang of 1- % [1]. ic In invrtd scnarios, th cold plasma thory placs th ion-ion hybrid layr R ii and th associatd lft-hand cut-off R btwn th minority ion cyclotron rsonanc R ic and th Lcut off LFS antnna [13] [14] (s illustration on Figur 1a), with R ii moving to th LFS whn th minority ion concntration is incrasd. In this cas it is not immdiatly obvious which will b th prfrntial hating rgim. Abov a crtain minority ion concntration, whn th MH rgim singl-pass damping is vry wak, th MC rgim is xpctd to dominat. In particular, for high minority ion concntration (> %), and if th plasma configuration is chosn in such a way that th minority ion cyclotron rsonanc is not locatd in th plasma, it has bn shown on various tokamaks that fficint MC hating could b obtaind [15][16]. Nvrthlss, at vry low minority ion concntration, whn R ic and R ii ar nar ach othr, it is not obvious whthr th FW will b dominantly mod convrtd or absorbd by th minority ion population. Indd, vn if R ii is first ncountrd by th FW, th MH rgim can occur if th minority ions hav a tmpratur sufficintly high to Dopplr broadn R ic byond of th lft-hand wav cut-off. 5

6 Sction rports on ICRF hating xprimnts prformd in H plasmas in which th 3 H concntration was scannd from.5 % to 1 %. Th minority hating rgim obtaind for concntrations blow % as wll as th transition to th mod convrsion rgim ar studid. Sction 3 rports on ICRF hating xprimnts with D minority ions in H plasmas. Th strong influnc of carbon impurity ions in this schm is highlightd. Not that a concis summary of ths two sts of xprimnts has bn givn in [4]. Finally, prliminary rsults from numrical simulations of ths two hating schms with th 1-D cod TOMCAT and th -D full-wav cod CYRANO ar prsntd in sction 4. ICRF hating of H plasmas with 3 H Minority ions.1 Exprimntal st-up. Th xprimnts wr carrid out in H plasmas (with a small concntration of D from wall rcycling ( n / n ) stimatd of th ordr of 1- %) in th JET singl-null divrtor D configuration with th following paramtrs: minor radius of.9 m, major radius of th magntic axis around 3 m, toroidal vacuum magntic fild at.96 m (B t ) of 3.6 T, plasma currnt (I p ) of MA and cntral lctron dnsity (n ) around m -3. As discussd in th introduction, th 3 H concntration is on of th critical paramtrs influncing th FW damping. Hnc its control and dtrmination was crucial for ths xprimnts. As 3 H gas is lost through transport, kping th concntration at a spcific lvl rquirs 3 H gas to b injctd into th machin during th discharg [1]. A vry fficint way to do this is to us th JET ral-tim cntral controllr (RTCC) in ordr to link a masurmnt of th 3 H dnsity to th opning of th gas injction valv. This tchniqu, dvlopd in th last fw yars [17], has bn succssfully usd in th xprimnts prsntd hr to control th 3 H concntration down to lvls as low as 1.8 %. Th 3 H concntration ( n / n H 3 ) was stimatd from th ffctiv charg of th ions and th rlativ concntration 6

7 of th majority and minority ions masurd using th rspctiv charactristic light mission in th divrtor. Iron, argon, nickl, oxygn and carbon impuritis wr takn into account through th radiation spctromtr data. It should b notd that whn a vry low 3 H concntration (< 1%) was rquird, it was only ncssary to injct 3 H bfor th ICRF hating phas. Up to 5 MW of ICRF powr ( P ICRF ) was applid using th four JET A ICRF antnnas [18] at a nominal frquncy of 37 MHz, positioning th fundamntal 3 H cyclotron rsonanc layr R ic ( 3 H) nar th plasma cntr (s Figur ). Each ICRF antnna is fd by four transmission lins with slightly diffrnt lctrical lngths connctd to on gnrator. Th four antnnas ar opratd at slightly diffrnt frquncis around th nominal on in ordr to prvnt cross-talk btwn gnrators, and also bcaus small frquncy variations ar usd in combination with lin strtchr and stub adjustmnts in th ICRF systm matching algorithm [19]. Th xact frquncis usd ar summarisd in Tabl 1 togthr with th corrsponding 3 H cyclotron rsonanc major radii. In particular, bcaus th frquncy of antnna D diffrs significantly from th othr thr, a sprad of about 1 cm is obtaind in th rsonanc positions. Dipol phasing of th ICRF antnnas was usd to launch wavs with a symmtric toroidal mod numbr ( n ϕ ) spctrum and with n 7 at th maximum of th antnna powr spctrum. Asymmtric toroidal mod numbr spctra with n 14 at th maximum of th antnna powr spctrum wr obtaind with th +9º antnna phasing (prdominantly in th co-currnt dirction) and -9º antnna phasing (launchd wav prdominantly in th countr-currnt dirction). In all ths pulss 1.3 MW of H nutral bam injction (NBI) was addd in ordr to allow masurmnts of ion tmpratur profils using th dg charg-xchang diagnostic (th charg xchang diagnostic viwing th plasma cor was not availabl for th xprimnts dscribd). 7 ϕ ϕ

8 In ordr to xprimntally dduc th lctron powr dposition profils, th lctron tmpratur rspons to an ICRF powr modulation was analysd using a Fast Fourir Transform (FFT) tchniqu (usd to study th rspons of a systm to a priodic prturbation) and Brak-In-Slop (BIS) mthods (which only rquirs a stp chang in th powr lvl to stimat th absorption profils) [17][][1]. ICRF powr was modulatd during a.5 s priod at th bginning and at th nd of th ICRF powr flat-top with a frquncy of Hz and an amplitud of 5 % (s xampl on Figur 3). Th modulation priod τ mod =.5 s, was chosn much smallr than th nrgy confinmnt tim τ E (typically of th ordr of. s in th xprimnt dscribd in this papr) to nsur that th diffusion procsss occur on a much longr tim scal than τ mod. This allows th straightforward application of th BIS analysis on th ECE signals for stimating th powr dposition profils. Th lctron tmpratur T was masurd using an lctron cyclotron mission (ECE) htrodyn radiomtr [] with th numbr of channls rcntly incrasd to 96 in ordr to covr approximatly th full plasma radius. Th tim rsolution varis from. ms to 1 ms, th stimatd radial rsolution for ach individual channl is around -5 cm and th sparation btwn channls lowr than 1 cm. Evr sinc th installation of th divrtor, th cntr of JET plasmas hav bn displacd vrtically with rspct to th quatorial plan of th tokamak. As a consqunc, th ECE lin of sight (locatd about.13 m abov th machin midplan) passs blow th magntic axis by about.17 m (cf. Figur ). Whn doing FFT and BIS analysis, two radial co-ordinats wr availabl for data intrprtation: - Th actual major radius position at which th masurmnts ar mad. - Th major radius position corrsponding to th intrsction of th magntic surfac on which th masurmnts ar mad, with th horizontal plan passing through th magntic axis. 8

9 Th scond of ths co-ordinats wr usd for th lctron powr dposition profils prsntd in this papr as it illustrats th fact that th plasma cor is not diagnosd, thus avoiding misintrprtation of th data. Morovr, as fast tim volution of th dnsity profils wr not availabl, it was assumd that this quantity did not rspond to th rapid changs of th modulatd ICRF powr. Th total fraction of th ICRF powr dampd dirctly on lctrons was stimatd by intgrating th lctron powr dnsity profils drivd from th masurmnts ovr th plasma volum. For both FFT and BIS mthods, it was assumd that transport procsss occur on a tim scal much longr that th modulation priod [][3]. Finally, information on th prsnc of fast ICRF-acclratd ions was obtaind with gammaray (γ-ray) spctromtry analysis [4] and both low- and high-nrgy nutral particl analysis (NPA)[5].. 3 H minority hating rgim in H plasmas To stablish th fasibility of 3 H MH rgim in invrtd scnarios a st of dischargs was obtaind with 3 H concntration blow %. Figur 3 shows an ovrviw of thr dischargs with n 3 / < 1 % and diffrnt phasings of th ICRF antnnas: dipol, +9º and 9º. In H n ths pulss, th lctron tmpratur incras, th production of nutrons and th gammarays mission indicatd that a fast 3 H population was cratd and that 3 H MH rgim was obtaind. A maximum lctron tmpratur max T of 6. kv was rachd with +9º phasing and P ICRF = 5 MW. Cntral ion tmpratur masurmnts wr not availabl for ths xprimnts. Nvrthlss, as illustratd in Figur 4, X-ray crystal spctromtr data wr collctd at a major radius R = 3.5 m giving an ion tmpratur, T (3.5 m) kv to b compard with an lctron tmpratur at th sam location of T (3.5 m) 3.4 kv. Assuming standard L-mod profils, on can thn conclud that mainly lctron hating was obtaind with T < T. i i 9

10 Th prsnc of a fast 3 H ion population ld to an incras of th nutron rat ( R NT ) which, in H plasmas, rsults from th nuclar raction btwn th bryllium impuritis and 3 H ions with nrgy abov.9 MV, i.. 9 B( 3 H,n) 11 C. A much highr nutron rat was obtaind for th puls (+9º phasing) indicating a highr nrgy 3 H population compard to pulss 6331 (dipol phasing) and (-9º phasing), which hav similar ICRF powr, 3 H concntration and lctron dnsity. Th fast 3 H ion nrgy contnt ( W fast ) dfind as th prpndicular nrgy contnt in xcss of twic th paralll valu, i.. = W W //, was stimatd as four thirds of th diffrnc btwn th total plasma nrgy drivd from W fast diamagntic loop masurmnts W DIA = 3 W, and th total plasma nrgy drivd from 4 magntic calculations, W MHD = 3/ 4W + 3 W//, i.. W fast = ( WDIA WMHD ). This 3 calculation gav a fast 3 H ion nrgy contnt up to 6 % highr in th +9º phasing cas than in th -9º and dipol phasings cass. Mor information on th fast 3 H ion population was obtaind from th γ-rays producd by th nuclar ractions, firstly btwn 3 H ions with nrgy abov.9 MV and 9 B impurity ions and scondly btwn 3 H ions with nrgy abov 1.3 MV and 1 C impurity ions [4]. Th prsnc of a highr nrgy 3 H tail with +9º phasing was confirmd by th highr γ-ray missivity (shown on Figur 5) for puls than for pulss 6331 (dipol phasing) and (-9º phasing). In discharg 63319, also shown on Figur 5, th 3 H concntration was doubld with rspct to discharg Th incras by a factor of 1.7 in th γ-ray signal and nutron rat confirmd a highr fast ion population but with a lowr tmpratur tail. In this puls it was stimatd that th tail tmpratur was T.3 ±.1MV. tail Th prsnc of ICRF acclratd 3 H ions was also illustratd by th R NT, W DIA and max T dcras (s Figur 3 and Figur 5) following th dcras of th avragd ICRF powr during th ICRF powr modulation btwn t = 9 s and t = 9.4 s. High nrgy NPA confirmd 1

11 th xistnc of a fast 3 H population but th fluxs of 3 H ions wr too small to mak any dfinit conclusions on th 3 H distribution function. Information on th radial profil of th fast 3 H population was obtaind from γ-ray mission profils masurd with th JET nutron and γ-ray diagnostics [4], [6]. Ths consist of two camras, vrtical and horizontal, with nin and tn lins of sight, rspctivly. Th linintgral masurmnts of th γ-ray mission along th lins of sight wr tomographically rconstructd [7] in ordr to giv th local γ-ray missivity in a poloidal cross sction, as shown in Figur 6. Th rsults obtaind wr found in agrmnt with th past obsrvations of th ICRF-inducd orbit pinch ffct in prsnc of toroidally dirctd wavs [8][9][3]. In th +9º phasing cas, th inward pinch of th rsonant trappd ion orbits turning points lads to dtrapping and producs a significant numbr of high-nrgy non-standard passing ions on th low fild sid of th rsonanc [31]. In th 9º phasing cas, which corrsponds to an ICRF-inducd outward pinch, th standard trappd orbits dominat and th turning points of th orbits mov outwards along th rsonanc layr lading to a narrowr and mor longatd γ-ray profil (s Figur 6). It should b notd that in both pulss with +9º phasing (63313 and 63319), toroidal Alfvén ignmods (AEs) with frquncis btwn and 6 khz wr obsrvd during th ICRF powr flat-top whil in th pulss with dipol (6331) and 9º phasing (63314) such activity was not sn. Enrgtic ions can dstabilis AEs with th driv proportional to th radial prssur gradint of th fast ions at th location of th mod whn n ϕ ω > fast ω. Hr n ϕ is th toroidal mod numbr; ω is th mod frquncy and ω fast is th fast ion diamagntic frquncy, which is proportional to th radial prssur gradint of th nrgtic ion distribution function and incrass with th ffctiv tail tmpratur [3]. This suggsts that th pulss with +9º phasing ICRF wavs gnratd fast ions with mor pakd radial prssur profils and tails with nrgis high nough to xcit AEs. 11

12 .3 Transition from ICRF minority hating to MC hating As th 3 H concntration was incrasd abov % a rproducibl transition from th MH to th MC rgim was obsrvd. This transition to a diffrnt hating rgim was sn on svral diagnostic signals. First, as n / n 3 H was incrasd, th T rspons to th ICRF powr modulation gradually changd, indicating a chang in th powr dposition charactristics. In Figur 7, th tim volution of T at R =.8 m and th 3 H concntration ar plottd for puls 633 for which th ICRF modulation was applid throughout th ICRF powr flat-top. On can clarly s a dramatic chang in th T rspons as n 3 / n bcom largr than % (t 8. s). As discussd in th introduction, th finit slowing-down tim of fast ions on th lctrons in th MH rgim lads to a dlay in th tmpratur rspons with rspct to th ICRF powr modulation. In th MC rgim, lctron hating is a dirct procss H by ELD. Indd, on can s in Figur 7(b) that, for n / n 3 H 3. %, th T rspons is in phas with th powr modulation, consistnt with dominant dirct lctron hating. For n 3 / n H.8 % cas (s Figur 7(a)), th priod of th modulation of.5 s associatd with an stimatd fast 3 H slowing down tim of about.4 s prvnts us, as xpctd, from sing any clar T rspons. Th dcras in T obsrvd aftr th transition btwn th two hating schms (from t 8.5 s) indicats that th optimal conditions for fficint lctron hating ar diffrnt in th MC and MH rgims. In th following sction w show rsults in which th xprimntal conditions wr optimisd for th MC rgim. Th transition btwn MH and MC was furthr confirmd by th disapparanc of th fast 3 H population for n 3 / n > %. This was sn on th γ-ray mission (rquiring 3 H ions H with nrgy abov.9 MV) shown in Figur 8 for th pulss 63319, 633 and 6334, which diffr only in 3 H concntration. In discharg 63319, a high signal was masurd 1

13 throughout th puls as th 3 H concntration stayd blow 1.8 %. In discharg 633, as n 3 / n H was incrasd abov % for t 6.3 s th γ-ray signal bgan to dcras to finally disappar. Almost no signal was collctd in discharg On can also notic in Figur 8, th small dcras in ICRF powr for puls 633 and th vry raggd ICRF powr for puls This prturbation in th powr was du to strong modification in th antnna loading as th ICRF wav absorption mchanism changd at th transition btwn th two rgims. Th % thrshold concntration was also confirmd by plotting th fast ions nrgy contnt for a larg rang of pulss with diffrnt ICRF phasing, total hating powr and magntic fild as a function of th 3 H concntration (s Figur 9). It should b notd that additional xprimntal data would b rquird to documnt mor prcisly th hating rgim transition btwn n 3 / n = % and n 3 / n =.5 % and invstigat th ffct of th antnna H H phasing. Indd, th width of th Dopplr-shift-broadnd 3 H absorption rgion as wll as that of th vanscnc layr btwn th ion-ion layr and th lft-hand cut-off (and hnc th convrsion fficincy) dpnds on th paralll wav numbr k // ~ nϕ / R (with R th plasma major radius). Consquntly, th critical minority concntration btwn th two rgims is xpctd to b diffrnt for diffrnt antnna phasings [33]. An stimat of th lctron dposition profils bfor and aftr th chang of hating rgim was obtaind with a BIS analysis of th puls 633 (prviously prsntd in Figur 7) for which th ICRF powr modulation was applid throughout th ICRF flat-top. As mntiond in th introduction, th BIS profils wr mappd onto th quatorial plan of th plasma. This is illustratd on th poloidal sctions prsntd in Figur 13, whr on can s that no tmpratur masurmnts wr availabl for major radius btwn.9 m and 3.1 m. Two lctron dposition radial profils ar shown in Figur 1, corrsponding to tims prcding 13

14 and following th hating rgim transition. Ths dposition profils wr obtaind from an upgradd BIS mthod [34], in which th phas lags btwn th powr modulation and th lctron tmpratur rspons, that occur during indirct lctron hating, ar takn into account maning that both indirct and dirct lctron dposition ar dducd. For n / n H 3.8 %, a broad profil was obtaind which sms to pak towards th undiagnosd plasma cntr. This is consistnt with indirct cntral lctron hating from th fast 3 H ions cratd at th 3 H cyclotron rsonanc layr R ic ( 3 H) m. Nvrthlss, th dposition profil obtaind was too broad to com from this hating alon. In ordr to find an xplanation, ths lctron dposition profils wr compard with th ons dducd from standard BIS and FFT analysis. Th upgradd BIS and th FFT mthods ar xpctd to giv similar rsults. Th standard BIS mthod, which nglcts any phas lag btwn th powr modulation and th lctron tmpratur rspons, givs only dirct lctron dposition. Consquntly, inconsistncis btwn FFT, upgradd BIS and standard BIS analyss can b usd as a diagnostic to indicat whr indirct hating is taking plac []. Th thr mthods wr thus compard and th rsulting lctron dposition profils for n 3 / n.8 % ar H shown in Figur 11. Btwn R = 3. m and R = 3.3 m, th FFT analysis and th nw BIS analysis agr but ar both in disagrmnt with th standard BIS analysis, indicating indirct lctron hating. From R = 3.3 m and on th LFS, th thr mthods agr, indicating dominant off-axis dirct lctron hating, pakd around 3.3 m. Dirct lctron hating nar R = m was also confirmd by th dcras in th tim dlays btwn th tmpratur rspons and th powr modulation, obtaind from th upgradd BIS mthod as a function of th major radius (Figur 1). A clar dcras in th tim dlay is found nar R = m. Th rason for such off-axis dirct lctron hating was attributd to b th prsnc of C impurity ions in th plasma, which hav th sam charg to mass ratio as th D minority ions. Not that th concntration of othrs impuritis with th sam charg to mass ratio as th C 14

15 ions was ngligibl compard to th C concntration ( n / n ) stimatd to b -3 %. As th D and C ions hav togthr th sam ffct on th FW propagation as a much highr D concntration, a nw ion-ion hybrid layr, notd (D,C)-H appard in th plasma whr th FW could b mod convrtd. In Figur 13(a) this nw ion-ion hybrid layr is rprsntd in th cas of % of C and % of D in a H plasma, with an additional.8% of 3 H. Th rsulting dirct absorption on th lctrons at R.6 m was thn obsrvd on th sam flux surfac LFS at R 3.3 m. Th intgratd powr absorbd by th lctrons was stimatd to b % and 3 % of th total ICRF powr from th standard and th nw BIS mthods rspctivly. Simulations prsntd in sction 4 of this papr will also confirm th prsnc of th (D,C)-H hybrid layr and its influnc. C For a highr 3 H concntration n 3 / n.6 %, th lctron powr dposition profil H (Figur 1 and Figur 13b) was much mor pakd and locatd at a major radius around 3.15 m, in agrmnt with th location of th 3 H-H hybrid layr associatd with.6% of 3 H in a H plasma. Th intgratd powr transfrrd to th lctrons was stimatd to b 6 %, 69 % and 71 % of th total ICRF powr from th standard BIS, th FFT and th nw BIS mthods rspctivly..4 Mod convrsion rgim in H plasmas In ordr to furthr invstigat th MC rgim, xprimnts wr prformd with a magntic fild lowrd to 3.3 T and a 3 H concntration of 3.5 %. Th rsulting 3 H-H hybrid layr was locatd at a major radius R.8 m instad of R 3.15 m in th prviously discussd pulss. NBI powr and thrfor T i masurmnts wr not availabl for ths pulss. An ovrviw of th rsults obtaind is prsntd in Figur 14 for dipol and +9º phasings. On can s that almost no nutrons wr producd, which mans that only a fw, if any, fast 3 H ions with nrgy abov.9 MV wr prsnt. For th sam rason, no γ-ray signal was collctd. 15

16 Furthrmor th NPA diagnostic, confirmd that no fast 3 H ions with nrgy abov 4 kv, wr producd during its tim window of masurmnts i.. 6 s to 9 s. Finally, th highst lctron tmpratur, up to 8.5 kv, was obtaind with 5 MW of ICRF powr in th dipol cas. Radial profils of th ICRF powr dnsity dirctly absorbd by th lctron wr dducd from BIS and FFT analysis of th tmpratur rspons to th ICRF modulation btwn 5.8 s and 6 s. Th profils from th upgradd BIS ar shown Figur 15 (similar profils whr obtaind with th standard BIS and FFT mthods). Thy show an ovrall highr powr dnsity for th dipol phasing puls (63384) than for th +9º phasing puls (63383) with a total powr intgratd up to th plasma dg stimatd about 8% to 63 % of th coupld ICRF powr, rspctivly. On may qustion th quality of th ECE data nar th plasma dg, hnc th dg bump on th profils of Figur 15. Howvr th intgratd powr insid a normalisd minor radius of.8 (6 % and 53 % of th ICRF coupld powr) shows similar trnd. 3 ICRF hating of D ions in H plasmas Th xprimntal st-up for ths xprimnts was similar to th on dscribd abov. Th xprimnts wr carrid out at a toroidal vacuum magntic fild at.96 m of 3.9 T, a plasma currnt of MA and a cntral lctron dnsity of m -3. Th D minority concntration rsultd from D ion dsorption from th wall, th lgacy of prvious D plasma opration, and was stimatd to b n / n = 1- %. In ordr to position th fundamntal D cyclotron D rsonanc in th plasma cntr (R 3.1 m), ICRF wavs at a nominal frquncy of 9 MHz wr usd. Th xact oprating frquncis for th four antnnas and th corrsponding fundamntal D cyclotron rsonancs ar summarisd in Tabl. Dipol phasing of th antnnas was usd. 16

17 An ovrviw of a typical discharg is prsntd in Figur 16. Th coupling of th ICRF powr was vry challnging in this st of xprimnts and only brif paks at a maximum valu of.5 MW wr achivd. Most of th tim th avragd coupld powr was around 1.5 MW. Th first rason for this powr limitation coms from th fact that 9 MHz is nar th limit of th gnrator capability. Scondly, th antnna coupling rsistanc was unusually low and unstady indicating poor wav absorption. Strikingly, no D fast ions wr dtctd, ithr by th nutral particl analysr or th γ-ray mission. No nutrons wr dtctd and th maximum lctron tmpratur obtaind was around 3 kv. BIS analysis prformd on svral pulss rvald, as illustratd in Figur 17, a rathr pakd lctron powr dposition profil maximum at R 3.5 m and with a full width at half maximum of around 3 cm. Th total powr absorbd by th lctrons was stimatd to b 5 % of th ICRF powr. This off-axis lctron hating could only b xplaind by th prsnc in th plasma of -3 % of C, lading dirctly to th mod convrsion rgim. Th ffct of % of C on th disprsion rlation is shown on Figur 18. On Figur 18(a) th disprsion rlation is plottd with n D / n = % and in Figur 18(b) with D n n / = % and n C / n = %. Whn adding % of C, th ion-ion hybrid layr R ii is movd to th LFS at a major radius of around 3.5 m. Th fast wav is thn mod convrtd bfor raching th D cyclotron rsonanc layr, prvnting any D minority hating. No optimisation of this mod convrsion hating schm was attmptd mainly bcaus lowring th magntic fild to position th mod convrsion layr mor cntrally would hav introducd th 3 H ion cyclotron rsonanc in th plasma. 4 Numrical simulations Simulations hav bn prformd with th 1-D cod TOMCAT [35] and th -D full wav cod CYRANO [36] to aid in th intrprtation of th xprimntal rsults. TOMCAT is a finit lmnt cod basd on a variational principl for studying on-dimnsional fast wav 17

18 propagation and damping nar th ion-ion hybrid convrsion layr in tokamaks [35]. Finit Larmor radius (FLR) corrctions up to scond ordr in ρ Lk, whr ρ L is th Larmor radius, ar takn into account in th xpansions of th RF fild and of th Galrkin tst function componnts apparing in this formulation. This accounts for th fast and slow wav mods, as wll as finit tmpratur mods. Toroidicity and obliqu wav incidnc ffcts ar includd; hnc TOMCAT corrctly dscribs th physics of 1-D convrsion physics. Howvr, th absorption of th mod convrtd wav is not adquatly modlld bcaus poloidal magntic fild ffcts ar nglctd. CYRANO is a -D full-wav cod in toroidal gomtry including th finit lctron mass, FLR corrctions up to scond ordr in ρ Lk and an accurat dscription of poloidal magntic fild ffcts, such as a spcific k // for ach poloidal RF fild mod, and th rsulting incras of lctron Landau damping and TTMP for high poloidal mod numbrs [36]. Maxwll s quations for th wav fild ar solvd using Fourir sris in th poloidal and toroidal dirctions and a finit lmnt mthod. W strss that modlling mod convrsion to short wav mods in two dimnsions is a vry challnging problm, th adquat tratmnt of which has rcntly startd by appaling to massivly paralll computrs [37]. Th CYRANO rsults prsntd hr ar accordingly prliminary for th MC rgim, bcaus our prsnt computr capability only allows a partial numrical rsolution of th short mod convrtd wavs in th poloidal dirction for a larg tokamak such as JET. Ths simulations will b raddrssd in a futur papr as soon as adquat computr powr bcoms availabl to us. 4.1 Modlling of ICRF hating of H plasmas with 3 H Minority ions CYRANO and TOMCAT simulations wr prformd with paramtrs matching th xprimnts dscribd in sction.3, i.. a magntic fild at th magntic axis of 3.6 T, a cntral lctron dnsity of m -3, an ICRF frquncy of 37 MHz (rsulting in a cntral 18

19 3 H ion cyclotron rsonanc) and svral valus of th 3 H concntration ( n 3 / n btwn.5 % and 1 %). As xpctd th simulations rproduc a transition from dominant 3 H to dominant lctron absorption as th 3 H concntration incrass. Th introduction in th simulations of D concntrations up to %, rprsntativ of th xprimntal conditions, did not show any significant influnc on th hating scnarios. Nxt, maintaining th D concntration at %, th 3 H concntration scan was rpatd with H carbon concntrations n / n = 1 % and %. As discussd in sction.3 th addition of small C amounts of C introducs th (D,C)-H hybrid layr in th plasma. Not that any impurity with Z/A =1/ has a similar ffct. Th simulations show that th C impurity contnt of th plasma can indd considrably influnc th ICRF powr absorption, in particular for vry low 3 H concntrations in th MH rgim. Th rlativ powr fractions absorbd by th lctrons and th 3 H ions obtaind by CYRANO for % and % of C (both with % of D), ar prsntd in Figur 19 for th dominant toroidal mod numbr of dipol phasing, n = 7. If on considrs that th transition btwn th MH and th MC rgims occurs whn th absorption by th 3 H ions bcoms smallr than th absorption by th lctrons, on ss that in th ϕ absnc of C th transition occurs for n 3 / n 5 %. As soon as C ions ar includd th 3 H H lvl at which th transition occurs dcrass. Whn n / n = 1 % is assumd (not shown) th C transition occurs at around n 3 / n 4 %. With n C / n = %, th transition occurs nar H n 3 / n H 3 %, in bttr agrmnt with th valu obtaind in th xprimnts (for which th C concntration was stimatd around -3 %). Similar transition lvls hav bn obtaind with TOMCAT. Th fact that th 3 H lvl at which th transition occurs dcrass whn incrasing th C concntration can b xplaind if on kps in mind that th powr absorbd by th lctrons includs powr from th mod convrtd wavs associatd with th 3 H-H hybrid rsonanc but also from th mod convrtd wavs associatd with th (D,C)-H hybrid 19

20 rsonanc (FW ELD/TTMP is found to b ngligibl in th prsnt conditions). Not that bcaus of th plasma quasi-nutrality, for a fixd 3 H concntration, th introduction of carbon ions dcrass th H concntration and thus slightly incras th ratio n / n 3 H H. Nvrthlss, th ffct on th 3 H-H hybrid layr appars to b minor. In figur 19, for n 3 / n H =.5 % and without C, almost all th powr is absorbd by th 3 H ions and non is dirctly absorbd by th lctrons. Whn including % of C, 3 % of th powr gos to th lctrons bcaus of MC at th (D,C)-H hybrid layr. As a mattr of fact, this parasitic dirct lctron hating was highlightd xprimntally by th BIS analysis of th tmpratur rspons in th 3 H MH rgim (s paragraph.3 and discussion of Figur 1). Both cods show that whn th C impurity is takn into account, th 3 H absorption is maximum for 3 H concntration n 3 / n ~ %. Th strong incras of lctron H absorption rsulting from th introduction of % of C and from th associatd MC at th (D,C)-H hybrid layr is obsrvd for up to n 3 / n ~ 5 %. Abov this concntration, thr is H no diffrnc in th lctron absorption with and without C, maning that th fast wav is thn mainly mod convrtd at th 3 H-H hybrid layr. Furthr simulations wr prformd with TOMCAT in similar conditions as th MC xprimnts dscribd in sction.4, i.. a magntic fild at th magntic axis of 3.3 T, a cntral lctron dnsity of m -3, an ICRF frquncy of 37 MHz (rsulting in a HFS 3 H ion cyclotron rsonanc) and % of C ions. Th powr transfrrd to th lctrons (P ) and to th 3 H ions (P 3H ) was compard for two 3 H concntrations ( % and 3.5 %), thr plasma targt tmpraturs (3 kv, 5 kv and 8 kv) and two toroidal mod numbrs ( n = 7 and n φ = 14 ). Th rsults ar summarisd in Tabl 3, which givs th powr fractions associatd with th FW launchd on th LFS of th plasma and allowd to rflct onc on th HFS cut- φ

21 off, i.. doubl-pass absorption powr fraction. For th lowr 3 H concntration n 3 / n = H %, th powr absorbd by th lctrons P is intrstingly highr for th toroidal mod numbr n = 14 corrsponding to th +9º phasing than for n = 7 corrsponding to th φ dipol phasing. In both cass, th absorbd powr profils show that MC at th 3 H-H hybrid layr is ngligibl and that th main rason for lctron absorption is MC at th (D,C)-H hybrid layr. Th mor fficint convrsion in th +9º cas can b xplaind by th disprsion rlation shown in Figur. On can s that for n = 14 (Figur b) th FW right-hand cut-off is on th HFS of th (D,C)-H hybrid layr x((d,c)-h), allowing a mor fficint mod convrsion compard to th n = 7 cas (Figur a) for which th FW has φ φ φ to tunnl through its right-hand cut-off bfor raching x((d,c)-h). For n 3 / n = 3.5 %, and H plasma targt tmpraturs of 3 and 5 kv, th powr absorbd by th lctrons is 35 to 4 % highr for th dipol than for th +9º phasing. Morovr if in th dipol phasing cas, this powr is mainly du to MC at th 3 H-H hybrid layr, in th +9º cas, th powr absorbd by th lctrons is qually du to MC at th (3H-H) and (D,C)-H hybrid rsonancs. Th highr MC fficincy at 3 H-H hybrid layr for dipol phasing is in agrmnt with th xprimntal data prsntd sction.4. For n 3 / n = 3.5 %, and plasma targt tmpraturs of 8 kv, on H notics a significant incras in th doubl-pass absorption by th 3 H ions which gos from 1 % with 5 kv to 45 % with 8 kv and an associatd dcras in th lctron absorption from 7 % to 43 %. 4. Modlling ICRF hating of D ions in H plasmas TOMCAT simulations wr prformd for th xprimntal conditions of sction 3 (magntic fild of MA, a cntral lctron dnsity of m -3, an ICRF frquncy of 37 MHz) and a toroidal mod numbr n 7 corrsponding to th paks of th antnna powr spctrum of φ dipol phasing. For D concntration n D / n = %, a C concntration scan was prformd with 1

22 n c / n = %,.5 %, 1 %, 1.5 % and %. Th powr fractions absorbd by th lctrons and th D ions ar shown in Figur 1 as a function of th C concntration. This rsults clarly illustrat th strong rduction of th D absorption obtaind by adding ~1 % of carbon impurity ions to th % of D minority ions. Th dltrious influnc of vn vry small concntration of carbon for th (D)H hating schm is thus manifst. Howvr, in th xprimnts dscribd in sction 3., th powr fraction absorbd by th lctrons was stimatd ~ 5 % of th total absorbd powr whras th 1-D simulations givs 1%. This diffrnc is likly to b rlatd to th modst to poor absorptivity of th schm but cannot b xplaind in dtail from 1-D simulations. As manifst from th low and vry unstady antnna coupling during th xprimnts, wav absorption was indd quit poor, and th rsulting global pattrn of standing wavs in th tokamak had strong influnc on powr dposition [38]. Th high snsitivity of th absorption fficincy on th D and C contnt in th plasma and th lack of accuracy on thir xprimntal concntrations rndrs th intrprtation of this invrtd scnario vry dlicat. Th fat of powr channlld onto short wavlngth branchs has to b carfully assssd, accounting for ralistic profils, parasitic dg damping and -D wav propagation ffcts. This mor in-dpth analysis will b rportd in a futur papr.. 5 Conclusions Invrtd minority scnarios rlvant for th non-activatd phas of ITER in H plasmas hav bn invstigatd at JET. 3 H minority hating was succssfully achivd for n 3 / n blow H %. Whn n 3 / n was incrasd abov % th mod convrsion rgim dominatd. By H positioning th convrsion layr in th plasma cntr, lctron tmpraturs up to 8 kv wr obtaind using dipol phasing. D minority hating in H plasmas was also tstd. This scnario was not succssful as th prsnc of carbon impurity ions ld dirctly to far off-axis fast

23 wav mod convrsion. Prliminary numrical analysis indicats that concntrations as low as.5 %, suffic to prvnt an fficint absorption at th D minority cyclotron rsonanc layr. This ffct virtually ruls out th (D)H scnario for th non-activ phas of ITER, laving ( 3 H)H as th only viabl choic. Finally, th cod intrprtation of th xprimnts is in progrss but computationally challnging du to th prsnc of short mod-convrtd wavs. 3

24 Acknowldgmnts This work has bn conductd undr th Europan Fusion Dvlopmnt Agrmnt. It is a plasur to thank our collagus who opratd th tokamak, th hating systms and th diagnostics during th xprimnts. Th work carrid out by th UKAEA prsonnl was jointly fundd by th Unitd Kingdom Enginring and Physical Scincs Rsarch Council and by Euratom. Th work of E. Lrch was supportd by th EU undr an Euratom Intra- Europan Fllowship. 4

25 Rfrncs [1] ITER Physics Basis Editors, ITER Physics Exprt Group Chairs and Co-Chairs and ITER Joint Cntral Tam and Physics Intgration Unit, Nucl. Fusion 39, (1999) 1 [] Start D.F.H. t al., Nucl. Fusion 39(3) (1999) 31 [3] Lamall P.U. t al., Proc. of th 31 st EPS Conf. on Plasma Phys., London, 8 Jun - July 4, ditd by P. Norrys and H. Hutchinson, Europan Physical Socity, ECA Vol. 8G, (4) P and [4] Lamall P.U. t al., Nucl. Fusion 46, (6) [5] Stix T.H., Wavs in plasmas, Amrican Institut of Physics Prss, Nw York, 199, ISBN [6] Stix T.H., Plasma Phys. 14 (197) 367 [7] Prkins F.W., Nucl. Fusion 17(6) (1977) [8] Nlson-Mlby E. t al., Phys. Rv. Ltt. 9(15) (3) 1554 [9] Jagr E.F. t al, Phys. Rv. Ltt. 9(19) (3) 1951 [1] Lin Y. t al., Plasma Phys. and Control. Fusion 45 (3), ] [11] Ram A.K. and Brs A., Phys. Fluids B 3 (1991) [1] Mantsinn M.J., Mayoral M-L., Van Estr D. t al., Nucl. Fusion 44 (4) [13] Stix T.H., Nucl. Fusion 15 (1975) 737 [14] Majski R., Phillips C.F., Wilson T.R., Phys. Rv. Ltt 73 (1994) 4. [15] Bonoli P. t al., Phys. Plasmas 4(5) (1997) [16] Saoutic B. t al., Phys. Rv. Ltt. 76(1) (1996) [17] Van Estr D. t al., Proc.of 15 th Conf. on Radio-Frquncy Plasmas, Moran, Wyoming, 19-1 May 3, ditd by Cary B. Forst, Amrican Institut of Physics, Mlvill, Nw York, Vol. 694, 4 and [18] Kay A. t al., Fusion Eng. and Dsign 4 (1994) 1 5

26 [19] Wad T.J., Jacquinot J., Bosia G., Sibly A. and Schmid M., Fusion Eng. and Dsign 4 (1994) 3-46 [] Gambir D.J. t al, Nucl. Fusion 3 (199) 3-4 [1] Van Estr D., Plasma Phys. and Control. Fusion 4 (4) [] D la Luna E. t al,. Rv. Sci. Instrum. 75(1) (4) [3]Mantica P. t al., in Fusion Enrgy (Proc. 19 th Int. Conf. Lyon, ) (Vinna: IAEA) CD-ROM fil EX/P1-4 and [4] Kiptily V.G. t al, Nucl. Fusion 4 () [5] Korotkov A.A., Gondhalkar A. and Stuart A.J. 1997, Nuclar Fusion [6] Jarvis O. N. t al., Nucl, Fusion 36(11) (1996), [7] Ingsson L.C. t al., Nucl. Fusion 38(11) (1998) [8] Chn L., Vaclavick J. and Hammtt G., Nucl. Fusion 8(3) (1988) [9] Eriksson L.-G. t al., Phys. Rv. Ltt. 81(6) (1998) [3] Mantsinn M.J. t al., Phys. Rv. Ltt. 89(11) () [31] Hdin J., Hllstn T., Eriksson L.-G. and Johnson T., Nucl. Fusion 4 () [3] Krnr W. t al., Nucl. Fusion 38(9) (1998) [33] Wsson J., Tokamaks, scond dition, Oxford nginring scinc sris 48, Clarndon Prss, Oxford, 1997, ISBN [34] Lrch E. A. and D. Van Estr, Extnding th brak-in-slop analysis to indirct hating rgims in tokamaks submittd to Plasma Phys. and Control. Fusion in 5 [35] Van Estr D. and Koch R., Plasma Phys. and Control. Fusion 4(11) (1998) [36] Lamall P.U., LPP-ERM/KMS Lab. Rport 11, Brussls (1994) [37] Wright J.C., Bonoli P.T., Brambilla M. t al, Physics of Plasmas 11(5) (4) [38] Monakhov I., Bcoult A., Fraboult D. and Nguyn F., Physics of Plasmas 6(3) (1999)

27 Tabl Antnna A Antnna B Antnna C Antnna D Frquncy (MHz) R ic ( 3 H) (m) at 3.6 T R ic ( 3 H) (m) at 3.3 T Tabl 1: Oprating frquncis for th four ICRF antnnas and corrsponding 3 H cyclotron rsonanc major radii, for B t = 3.6 T and 3.3 T. Antnna A Antnna B Antnna C Antnna D Frquncy (MHz) R ic (D) (m) at 3.9 T Tabl : Oprating frquncis for th four ICRF antnnas and corrsponding D cyclotron rsonanc major radii, for B t = 3.9 T. n ϕ = 14 n ϕ = 7 T (kv) [ 3 H] (%) P (%) P 3H (%) P (%) P 3H (%) Tabl 3: Total doubl-pass lctron and 3 H powr hating powrs calculatd using th TOMCAT simulation cod for diffrnt plasma targt tmpraturs (3, 5 and 8 kv) and 3 H concntrations of and 3.5 % 7

28 Figur captions Ral (n ) log scal n 3H /n =1% - n = m -3 B t = 3.6T - Dipol phasing - f ICRF = 37MHz (a) ( 3 H)H R ic (D) R Rcut-off SW FW FW R ic ( 3 H) R ii R Lcut-off SW R Rcut-off RF ANTENNA Ral (n ) log scal (b) ( 3 H)D SW FW FW R ic (D) R Rcut-off R ii R Lcut-off R ic ( 3 H) R Rcut-off sw Major radius (m) RF ANTENNA JG5.44-1c Figur 1. Ral part of th squar of th prpndicular rfractiv indx obtaind from th rsolution of th cold plasma disprsion rlation. Fast wav (FW) and a short wav (SW) branchs ar rprsntd. Th following radial locations ar indicatd: FW lft-hand cut-off R Lcut-off ; FW right-hand cut-off R Rcut-off ; FW rsonanc R ii ; ion cyclotron rsonanc R ic.(a) illustrats th invrtd MH scnario ( 3 H)H and (b) th standard MH scnario ( 3 H)D. Not: th vrtical axis is linar for ( Ral( n ) << 1 and logarithmic for R al( n ) >> 1. In th lattr cas its corrsponds to sign(ral( n ))log((ral( )). n 8

29 Figur. Tokamak poloidal cross-sction with locations of th 3 H cyclotron rsonanc layr R ic ( 3 H) and of th D cyclotron rsonanc layr R ic (D) for discharg 6331 with B t = 3.6 T and an ICRF frquncy of 37 MHz. Th ICRF antnna and th lin of sight for th ECE lctron tmpratur masurmnts ar also shown. 9

30 (1 1 m -1 ) (MJ) (kv) (1 19 m - ) (MW) nl ( 3 H)H 3.6T/MA 37MHz n 3 H /n.5% Puls No: 6331: dipol Puls No: 63313: +9 o Puls No: 63314: -9 o max T W DIA R NT NBI ICRF Tim (s) Figur 3. Tim volution of th ICRF and NBI powr (H bams), cntral lin intgratd dnsity from th far infrard intrfromtr diagnostic (th cntral dnsity n, from LIDAR Thomson Scattring, was n = m -3 for pulss 6331 and 63314; LIDAR data wr not availabl for th puls 63313), maximum lctron tmpratur from th ECE Michlson intrfromtr diagnostic, plasma diamagntic stord nrgy and nutron rat from 9 B( 3 H,n) 11 C raction. Thr dischargs ar rprsntd for diffrnt ICRF antnna phasings: JG5.13-1c dipol, +9º and 9º. 3

31 ( 3 H)H 3.6T/MA 37MHz n 3 H /n ~.5% Puls No: 6331: dipol Puls No: 63313: +9 o Puls No: 63314: -9 o T (kv) T i Major radius (m) JG5.44-3c Figur 4. Radial profils of th lctron tmpratur (from th ECE htrodyn radiomtr at around.17 m blow th magntic axis). Th ion tmpratur data at R = 3.5 m ar masurd with a X-ray crystal spctromtr. Th ion tmpratur profils at th plasma dg ar masurd by dg charg xchang rcombination spctroscopy. 31

32 ( 3 H)H 3.6T/MA 37MHz Puls No: 6331: dipol Puls No: 63314: -9 o Puls No: 63313: +9 o Puls No: 63319: +9 o 1. (1 1 s -1 ) (%) (MW) (a.u.) n 3 H /n R NT NBI 6 7 Tim (s) ICRF 8 9 JG5.13-c Figur 5.Tim volution of th γ-ray missivity, ICRF and NBI powr, 3 H concntration and nutron rat for pulss 6331 (dipol), 63313(+9º), ( 9º) with 3 H concntration blow 1 % and puls (+9º) with 3 H concntration up to 1.8 %. 3

33 (a) +9 o phasing Puls No: t = 9s (b)-9 o phasing Puls No: t = 7s x1 1 m Z(m) Z(m) R ic ( 3 H) R ic ( 3 H) R(m) R(m) JG5.44-4c 1 Figur 6. γ ray mission profils (normalisd to th pak valu) for a +9º phasing cas (puls 63313) and a 9º phasing cas (puls 63314). A numbr of flux surfacs ar shown in grn; a grn cross indicats th magntic axis. Th 3 H ion cyclotron rsonanc layr R ic ( 3 H) is also rprsntd. 33

34 n3h /n (%) T (kv) ICRF Mod (a.u.) 4.5 Puls No: 633: +9 o ( 3 H)H 3.6T / MA 37MHz R ~.8m Tim (s) (a) n 3H /n ~.8% (b) n 3H /n ~ 3.% T (kv) Tim (s) Tim (s) 9.3 JG5.44-5c Figur 7. Tim volution of th ICRF powr modulation, lctron tmpratur at R =.8 m from ECE masurmnts and 3 H concntration for th puls 633 (+9º phasing). Zooms on th lctron tmpratur rspons to th ICRF powr modulation ar also rprsntd for (a) n 3H /n.8 % and (b) n 3H /n 3. %. 34

35 ( 3 H)H 3.6T/MA 37MHz +9 o Puls No: Puls No: 633 Puls No: 6334 (a.u.) 1 (MW) (1 1 s -1 ) (%) 5 ICRF NBI 1 n 3H /n 6 5 R NT Tim (s) JG5.13-4c Figur 8. Tim volution of th γ-ray missivity, ICRF and NBI powr, 3 H concntration and nutron rat for pulss 63319, 633,

36 +9 o +9 o +9 o +9 o.4-9 o dipol for P ICRF = 5MW, P NBI = 1.3MW, B t = 3.6T for P ICRF ~ 4MW, P NBI = 1.3MW, B t = 3.6T dipol for P ICRF = 5MW, B t = 3.6T dipol for P ICRF = 5MW, B t = 3.3T.3 W fast (MJ) n 3H /n (%) Figur 9. Fast ion nrgy contnt as a function of th 3 H concntration for a st of dischargs with diffrnt ICRF antnna phasings, total hating powr and toroidal magntic fild. W fast = W - W // was drivd from th total plasma nrgy from diamagntic masurmnts, W DIA = 3/ W, and from magntic calculations, W MHD = 3/ W + 3/ W //, i.. W fast = 4/3 (W DIA - W MHD ). JG5.44-6c 36

37 ( 3 H)H Puls No: o B t = 3.6T n 3 H /n ~.8% t = 6-6.3s n 3 H /n ~.6% t = s Powr dnsity (MW/m 3 pr MW launchd) Ric( 3 H) Rii( 3 H-H) Major radius (m) JG5.44-7c Figur 1. Elctron dposition profils from upgradd BIS analysis at two diffrnt 3 H concntrations for th puls 633. Th triangls corrspond to n 3H /n.8 % (MH rgim). Th dots corrspond to n 3H /n.6 % (MC rgim). Th 3 H cyclotron rsonanc layr R ic ( 3 H) and th 3 H-H hybrid layr R ii ( 3 H-H) ar also rprsntd. 37

38 ( 3 H)H Puls No: o Bt = 3.6T t = 6-6.3s n 3H /n ~.8% standard BIS -> dirct lctron hating nw BIS FFT n=1- > dirct + indirct lctron hating Powr Dnsity (MW/m 3 pr MW launchd) Major Radius (m) JG5.44-8c Figur 11. Elctron dposition profils from thr diffrnt mthods: standard BIS, nw BIS and FFT. Th nw BIS analysis taks into account dlays in th lctron tmpratur rspons to th ICRF powr modulation. Th FFT and th nw BIS mthod accounts for dirct and indirct lctron hating. Th standard BIS mthod accounts for dirct lctron hating only. Disagrmnt btwn th FFT (or th nw BIS) and th standard BIS mthods indicats indirct lctron hating at th location of th disagrmnt. 38