Assessment of erosion, deposition and fuel retention in the JET-ILW divertor from ion beam analysis data

Nuclea Ma e ials and Ene gy 12 (2017) 559–563 Con en s lis s a ailable a ScienceDi ec Nuclea Ma e ials and Ene gy jou nal homepage: www.else ie .com/loca e/nme Assessmen o e osion, deposi ion and uel e en ion in he JET-ILW di e o om ion beam analysis da a N. Ca a ino a , b , ∗, N.P. Ba adas a , c , V. Co egido a , b , A. Widdowson a , d , A. Ba on-Wiechec a , d , J.P. Coad a , d , K. Heinola a , e , M. Rubel a , , E. Al es a , b , JET Con ibu o s 1 a EURO usion Conso ium, JET, Culham Science Cen e, Abingdon OX14 3DB, UK b IPFN, Ins i u o Supe io Técnico, Uni e sidade de Lisboa, Lisboa 1049-001, Po ugal c C 2 TN, Ins i u o Supe io Técnico, Uni e sidade de Lisboa, E.N. 10, Saca ém 2686-953, Po ugal d Culham Cen e o Fusion Ene gy, Culham Science Cen e, Abingdon OX14 3DB, UK e Uni e si y o Helsinki, P.O. Box 64, Helsinki 00560, Finland Royal Ins i u e o Technology, Associa ion EURATOM-VR, S ockholm SE-100 44, Sweden a i c l e i n o A icle his o y: Recei ed 14 July 2016 Re ised 5 Oc obe 2016 Accep ed 22 Oc obe 2016 A ailable online 18 No embe 2016 keywo ds: JET ITER-like wall Plasma acing componen s E osion Deposi ion Ion beam analysis a b s a c Pos -mo em analyses o indi idual componen s p o ide ele an in o ma ion on plasma-su ace in e ac- ions like ungs en e osion, be yllium deposi ion and plasma uel e en ion wi h di e o iles ia implan- a ion o co-deposi ion. Ion Beam echniques a e ideal ools o such pu poses and ha e been ex ensi ely used o pos -mo em analyses o selec ed iles om JET ollowing each campaign. In his con ibu ion esul s om iles emo ed om he JET ITER-Like Wall (JET-ILW) di e o ollow- ing he 2013–2014 campaign a e p esen ed. The esul s summa ize e osion, deposi ion and uel e en ion along he poloidal c oss sec ion o he di e o su ace and p o ide da a o compa ison wi h he fi s JET-ILW campaign, showing a simila pa e n o ma e ial mig a ion wi h he excep ion o Tile 6 whe e he s ike poin ime on he ile was ∼4 imes longe in 2013–2014 han in 2011–2012, which is likely o accoun o mo e ma e ial mig a ion o his egion. The W deposi ion on op o he Mo ma ke coa ing o Tile 4 shows ha he en ichmen akes place a he s ike poin loca ion. ©2016 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license. ( h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/ ) 1. In oduc ion The u u e o usion eac o s will depend on he beha iou o he ma e ials used in Plasma Facing Componen s (PFCs) which will de e mine hei li e ime and also influence e en ion o hyd ogen iso opes in he essel. Among o he p ocesses, e osion o PFCs and subsequen e-deposi ion a e c i ical o he ope a ion o usion de- ices and mus be p ope ly unde s ood. The e osion and mig a- ion in he di e o is a complex sys em and de e mines he li e- ime o PFCs in usion de ices. E osion in he main chambe is he main sou ce o impu i ies in he plasma, i occu s by spu e ing o plasma ions wi h ene gies up o se e al keV and subsequen im- pac o e oded pa icles. The e oded ma e ial, mainly Be om he Be-coa ed iles, en e s he plasma, is ionised and anspo ed by ∗Co esponding add ess: IFPN/LATR, Ins i u o Supe io Técnico (IST), Uni e si- dade de Lisboa, Es ada Nacional N °10, km 139,7, Bobadela 2695-066, Po ugal. E-mail add esses: [email p o ec ed] , no be [email p o ec ed]. ulisboa.p (N. Ca a ino). 1 See he Appendix o F. Romanelli e al., P oceedings o he 25 h IAEA Fusion Ene gy Con e ence 2014, Sain Pe e sbu g, Russia he SOL-flows owa ds he di e o du ing he X-poin phase. This flow induces deposi ion o Be in he op pa o he inne di e - o . The p ocess o e-e osion/deposi ion keeps going un il i is de- posi ed on o emo e a eas and no longe in e ac s wi h he plasma. The numbe o cycles o e-e osion/deposi ion dec eases wi h he h eshold ene gy o he elemen , his means ha in emo es a eas we expec mo e C han Be, and only a small amoun o W [1] . The co-deposi ion o uel pa icles wi h e osion p oduc s leads o an inc ease in he i ium in en o y. Du ing he 2013–2014 JET-ILW campaign se e al ma ke iles we e ins alled in he main chambe and di e o o assess he global pic u e o e osion and e-deposi ion p ocesses occu ing du ing machine ope a ion [2–4] . The di e o is he egion whe e hese p ocesses a e expec ed o occu a ex eme condi ions and pos mo em analysis o e s he possibili y o e eal some o he majo e ec s. Fuel in en o y, ma e ial e osion and mel ing ha e a majo im- pac on he pe o mance o he di e o . A la ge numbe o diag- nos ic ools ha e been used o s udy hese phenomena. This s udy p esen s he esul s om Ion Beam Analysis (IBA) echniques such h p://dx.doi.o g/10.1016/j.nme.2016.10.027 2352-1791/© 2016 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license. ( h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/ ) 560 N. Ca a ino e al. / Nuclea Ma e ials and Ene gy 12 (2017) 559–563 Fig. 1. JET di e o du ing he JET-ILW campaign 2013–2014. The s-coo dina e (in mm) s a s a he uppe le co ne o Tile 0 and ollows he ile su aces. In blue, he iles s udied in his pape ; he Tile 1 is be ween s-coo dina es 162 mm and 415 mm, Tile 4 be ween s-coo dina es 713 mm and 934 mm and Tile 6 be ween s-coo dina es 1363 mm and 1552 mm. as Ru he o d Backsca e ing Spec ome y (RBS) and Nuclea Reac- ion Analysis (NRA) o uel e en ion and e osion pa e ns in JET. The esul s gi e in o ma ion on he p ocesses occu ing a he in- ne and ou e di e o co ne s as well as a he ansi ion om he inne main chambe wall (high field side) o he inne di e o . 2. Expe imen al de ails A selec ion o passi e diagnos ic componen s and ma ke iles we e ins alled in he JET chambe o he 2013–2014 campaign. The ile numbe s and loca ion in he di e o a e shown in Fig. 1 . In his wo k, esul s o di e o Tiles 1, 4 and 6, a e p esen ed, discussed and highligh ed. The iles a e solid s uc u es whe e he plasma acing su ace is shaped wi h fla segmen s a di e en an- gles. This in oduces some difficul ies in moun ing each ile o IBA which we e o e come by measu ing each o he fla segmen s sep- a a ely, i.e. he ile was moun ed in he chambe se e al imes us- ing specially designed holde s o o ien each su ace pe pendicula o he ion beam as shown in Fig. 2 . All posi ions on di e o iles a e loca ed using he s-coo dina e sys em ( Fig. 1 ), s a ing a he uppe le co ne o he High Field Gap Closu e ile (Tile 0) and ollowing he ile su aces om he inne o he ou e di e o . The di e o iles, wi h he excep ion o Tile 5, consis o CFC coa ed wi h 10 o 20 μm ungs en (W) on he plasma- acing su - aces [5,6] . Ma ke iles, like Tile 1, used o s udy e osion and de- posi ion in he di e o we e coa ed wi h a W ma ke laye wi h a hickness o abou 3 μm wi h a 3 μm hick molybdenum (Mo) in- e laye be ween he W ma ke laye and he hick W coa ing [6] . The Mo in e laye is necessa y o dis inguish he W ma ke laye om he W coa ing o dep h p ofiling me hods, he e o e enabling he e osion o W o be measu ed and he quan i a i e de e mina- ion o deposi ion o all elemen s. The da a p esen ed o Tile 4 a e om a ma ke ile whe e he op laye is 3 μm hick Mo (simila o Tile 1 bu whe e he op W laye is omi ed), which is used o enable he analysis o e-deposi ed W. E osion and deposi ion we e analysed by Ion beam Analysis (IBA) echniques using he 2.5 MV Van de G aa accele a o in- Fig. 2. Schema ic iew o a ma ke Tile 1. Due o he ile geome y h ee analysis scans we e made as indica ed in he diag am, in o de o minimize he e ec o he angle be ween he sample no mal and he di ec ion o he inciden beam. s alled a he Labo a o y o Accele a o s and Radia ion Technolo- gies o Ins i u o Supe io Técnico. Analyses o JET we e pe o med in a chambe dedica ed o usion esea ch, whe e samples, includ- ing ull JET iles, con amina ed wi h i ium (T) and be yllium (Be) can be handled. Elas ic Backsca e ing Spec ome y (EBS) and Pa icle Induced X- ay Emission (PIXE) we e pe o med wi h 2.3 MeV inciden p o- ons. RBS and NRA we e pe o med using 3 He ions a an ene gy o 2.3 MeV in o de o measu e he amoun s o 2 H (D), Be and C. The D( 3 He, p) 4 He eac ion was used o measu e he D con- en , he 9 Be( 3 He, p x ) 11 B (x = 0,1,2,3) eac ions [7] o Be and he N. Ca a ino e al. / Nuclea Ma e ials and Ene gy 12 (2017) 559–563 561 12 C( 3 He, p 0 ) 14 N eac ion o 12 C. Fo hin deposi s, he NRA da a p o ide mo e sensi i e and accu a e esul s o Be and C han he RBS da a, which a e used o hick deposi s. A 2.3 MeV he NRA c oss-sec ion o ca bon is e y low, and in he case o hick films he signal om C ( 12 C( 3 He, p 0 ) 14 N) o e laps wi h he Be signal ( 9 Be( 3 He, p 3 ) 11 B), limi ing i s de ec ion. The sample manipula o in he expe imen al chambe is ully au oma ed and enables analysis o e 150 mm along he su ace. This allows efficien measu emen o whole JET iles. The RBS pa - icle de ec o is loca ed a a sca e ing angle o 150 °The NRA de ec o is placed a a 135 °sca e ing angle and has an ac i e laye wi h 1 mm hickness. A 140 μm hick Al s opping oil was se- lec ed o allow he de ec ion o D and Be p o ons om he 2 H( 3 He, p 0 ) 4 He and 9 Be( 3 He, p x ) 11 B eac ions [7] whils s opping he 14 MeV αpa icles om he 9 Be( 3 He, α0 ) 8 Be eac ion. S aggling in he oil does no a ec he measu emen s since i is he signal in- eg al ha ca ies he in o ma ion on he c oss sec ion. The X- ays a e de ec ed by PIXE by means o a “Si ius 30” de ec o loca ed a a sca e ing angle o 150 °wi h a Myla fil e 350 μm hick. The iles we e scanned using EBS, RBS, NRA and PIXE, along he poloidal di ec ion as indica ed in Fig. 2 o Tile 1: spec a a e aken e e y 5 mm using a 1 mm beam spo size along he ile su ace o ha e a comple e pic u e o he composi ion. The expe imen al da a we e analysed using he NDF code [8] o quan i y all he impu i ies p esen in he iles. The sample compo- si ion is de e mined in a sel -consis en way wi h PIXE da a sim- ula ed by means o LibCPIXE code [9] . The PIXE da a we e anal- ysed wi h GUPIX code [10] and he esul s used as inpu wi h NDF- LibCPIXE. 3. Resul s The esul s a e p esen ed and discussed below o each o he iles indi idually. 3.1. Uppe inne di e o (Tile 1) On he W su ace Be deposi s mo e han 10 μm hick we e ound a he op o Tile 1 in he egion s = 162–296. In he fi s JET-ILW campaign his hick deposi was shown o be a laye ed s uc u e, wi h a ying Be and W concen a ions p obably due o ope a ions his o y [11] . The non-uni o m deposi ion and he su - ace oughness complica es he in e p e a ion o laye ed s uc u es by IBA, bu he o e all amoun o deposi ed ma e ial is measu ed, e.g. he o al a eal densi ies o he chemical species. I should be poin ed ou ha hick films end o cause p o on ene gy dispe - sion, no p o on pa icle loss, and some dispe sion can be ole - a ed; he 2.3 MeV inciden p o ons ha e insufficien ene gy o e- sol e he hickness o he Be deposi wi hou e o . The EBS da a oge he wi h PIXE and NRA gi e he concen a ion o he elemen s p esen in he laye . Dep h p ofiles a each analysis poin a e in e- g a ed o gi e he concen a ion along he su ace o Be, D, C and O in he fi s 5 ×10 19 a /cm 2 o ( ∼6 μm using he bulk densi ies and no malizing each densi y by he concen a ion o he co espond- ing elemen ); o e his in eg a ion dep h he beam doesn’ su e la ge ene gy dispe sion. These esul s a e shown in Fig. 3 . These hick deposi s ha e a complex and mul i-laye s uc u e, showing a simila pa e n o he fi s JET-ILW campaign [3] . The concen a- ion o Be a ies om 70% o 90%, D up o 6%, O and C om 1% o 10%. EBS p o on spec a show W and Mo a he su ace, bu a concen a ions below 1%. In he lowe pa o Tile 1 (s = 296–415 mm) he e is a small de- posi ion o Be, D, C, and O, which is difficul o quan i y. A simila pa e n o he fi s JET-ILW campaign was obse ed [12] . This de- posi ion is low due o compe i ion be ween deposi ion and e osion p ocesses occu ing in his egion. 3.2. Remo e inne co ne (Tile 4) Deposi s ich in D, Be, C and O as well as o he me als a e ob- se ed on Tile 4 in he plasma shadowed su ace, i.e. he fla e- gion o he ile below he slope (s = 713–762 mm), as shown in Fig. 3. Du ing X-poin plasmas neu als e ode Be om he inne wall. E oded Be becomes ionised and is anspo ed h ough he SOL [13] and is deposi ed in he di e o along wi h D and o he impu- i ies. On he plasma accessible su ace o he ile deposi ed ma- e ial is spu e ed and edeposi ed un il i mig a es o he emo e inne co ne . This can be seen in Fig 3 a whe e he Be hickness in he plasma accessible egion (s > 775 mm, see Fig 3 d) is nea ly one o de o magni ude lowe han in he emo e a ea (s < 775 mm). In addi ion he D con en is also educed in he plasma accessible su ace due o hea ing o he su ace [13] , as shown in Fig 3 b. The lowe h eshold ene gy o C and O compa ed wi h Be inc eases he numbe o cycles o e osion/deposi ion o hese elemen s and ex- ends hei ange gi ing highe concen a ions in emo e a eas (see Fig 3 c) compa ed wi h Be ( Fig 3 a). A he p edominan s ike poin posi ion s = 798 mm he Mo ma ke laye is e oded by ∼40% o he nominal hickness o 3 μm: he dis ibu ion o he s ike poin s and he Mo concen a ion a e shown in Fig. 4 d and c espec i ely. Ha ing a Mo op su ace allows W deposi ion o be mea- su ed. Th ee bands o W deposi ion in he o oidal di ec ion a e ound as shown in Fig. 4 b, one a he op o he sloping su - ace (s = 840 mm), a band a he p edominan s ike poin posi ion (s = 800 mm) and a band nea he co ne o he ho izon al su ace (s = 772 mm). Some e osion occu s on Tile 3 when he s ike poin is loca ed he e, as was obse ed a e ILW-1 [12] , and W e oded om his Tile may be anspo ed by he SOL-flows owa ds Tile 4 in subsequen discha ges o join W e oded locally om o he (W-coa ed) Tile 4 when he s ike poin is loca ed he e. Howe e , su ace W is seen on all analysed su aces in small quan i ies and gene ally in JET he mos likely W sou ce is e osion om he ou e di e o iles. Due o he highe h eshold o e-e osion, W is en- iched a he s ike poin loca ion, whe e he flux and impac en- e gy is insufficien o u he mig a ion in o he shadowed zone: howe e Mo will be p e e en ially spu e ed om his a ea as i has a lowe spu e ing h eshold ene gy o e-e osion. The hi d band esul s p obably om local e-deposi ion o he W on he ile. The es o he ile ( om s ≈840–934 mm), e eals a small amoun o deposi ion, and no e osion. This deposi ion pa e n is a li le bi di e en han obse ed in he p e ious ILW campaign 2011–2012 [14] mainly because o changes in he s ike poin dis ibu ion be- ween he campaigns. 3.3. Remo e ou e co ne (Tile 6) Deposi ion is also de ec ed in he plasma shadowed ou e co - ne o Tile 6, al hough ∼5 imes g ea e Be con en han on Tile 4 and ∼5 imes highe han obse ed on Tile 6 a e he 2011– 2012 campaign [15] . The di e ence in he Be amoun and p ofile [12] be ween bo h campaigns is due o an inc ease o he ime o he ou e s ike poin on Tile 6, ha is ∼4 imes longe in 2013– 2014 han in 2011–2012 as show in Fig 3 d. On Tile 6 he deposi ion was inhomogeneous wi h deposi ion p edominan ly a he bo om o he sloping egion in a band om s ≈1480 mm o s ≈1515 mm. Ni is obse ed in his deposi o he o de o 2 ×10 18 a /cm 2 likely due o some mel ing o Inconel ie ods in Tile 7. In he plasma shadowed a ea o Tile 6 he D, C and O a e p esen bu a lowe concen a ions han obse ed in he plasma shadowed a ea o Tile 4, ne e heless he deposi ion mechanism in his zone should be he same. On he uppe ho izon al su ace o he ile (s = 1363–1425 mm) he amoun o D dec eases an o - de o 1 ×10 17 a /cm 2 , he C and O a e in he limi o he EBS/NRA 562 N. Ca a ino e al. / Nuclea Ma e ials and Ene gy 12 (2017) 559–563 Fig. 3. To al deposi ion o (a) Be, (b) D, (c) C and O on he ma ke iles. The concen a ion o Tile 1 is he in eg a ed concen a ion in he fi s 5 ×10 19 a /cm 2 o sample. (d) S ike poin posi ions o he JET-ILW campaign 2011–12 and 2013–14. Fig. 4. Tile 4 (a) s-coo dina e be ween 713 mm and 934, showing he egions e- e ed o in he ex . (b) In eg a ion o W concen a ion in he fi s 10 19 a /cm 2 o he ile su ace (i.e. deposi ed on op o he ma ke ) (c) To al concen a ion o he Mo ma ke laye , and (d) a his og am o s ike poin posi ions o he JET-ILW cam- paign 2013 o 2014. sensi i i y. This su ace was pa ly shadowed by Tile 5 and was in he p i a e flux egion when he s ike poin was on ile 6. Tile 6 is a s anda d W coa ed ile, he e o e i is no possible o commen whe e e osion occu ed. 4. Conclusions Unde he p esen JET plasma condi ions, he uppe di e o e- mains he egion o highes deposi ion wi h Be ich films o e 10– 20 μm hick p esen a he op o Tile 1. Fuel e en ion in he de- posi s on Tile 1 emain simila o he 2011–2012 campaign wi h Be: D a io o he o de (10–15):1, ypically 5.0 ×10 19 a /cm 2 o Be o 0.3 ×10 19 a /cm 2 o D in he Be ich films. Be and D in he emo e inne co ne o he di e o (Tile 4) a e an o de o magni ude highe ( ∼5.0 ×10 18 a /cm 2 o D) han he maximum deposi ion seen beyond a he bo om o he sloping su ace ( ∼0.5 ×10 18 a /cm 2 o D), i.e., beyond s ≈770 mm. Su ace analysis o he Mo ma ke coa ing shows a W deposi ion in h ee loca ions: one a he p edominan s ike poin posi ion, one wi h he Be deposi s and one a he op o he sloping su ace. Deposi ion a he ou e co ne o he di e o also shows a maximum deposi ion a he u hes egion o he ile accessi- ble by he plasma. The maximum Be deposi ed in his band is 3 ×10 19 a /cm 2 , a ound ∼5 imes highe han obse ed in he 2011–2012 campaign o simila o al ime in di e o X-poin plasma - 13 h (2011–2012) compa ed wi h 14 h (2013–2014). How- e e he ime he ou e s ike poin was loca ed on Tile 6 was ∼ 4 imes longe in 2013–2014 han in 2011–2012, which is likely o accoun o mo e ma e ial mig a ion o his egion [16,15] . Acknowledgemen s 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- N. Ca a ino e al. / Nuclea Ma e ials and Ene gy 12 (2017) 559–563 563 a om esea ch and aining p og amme 2014–2018 unde g an ag eemen No 633053 . The iews and opinions exp essed he ein do no necessa ily eflec hose o he Eu opean Commission. 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