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On 23rd January 2006, the EFDA Associate Leader for JET Dr Jérôme Paméla presented the JET 2005 report and future programmein a seminar at the JET site. In his talk, Dr Paméla outlined the most recent news regarding fusion, the 2005 JET main events andscientific highlights, the 2006 JET programme, and planning beyond 2006.

"2005 was a key year for fusion with the decision on siting ITER in Cadarache taken by the parties on 28 June 2005. India joinedin November and ITER negotiations were completed in December 2005. The negotiation with Japan led to other projects beingjointly prepared between the European Union and Japan, the so-called ‘Broader Approach’, a very good opportunity for fasterdevelopment of fusion," stressed Dr Paméla.

Some of the scientific results obtained at JET in 2005, which were outlined in the talk, are presented in this Bulletin. The currentEuropean fusion research strategy, reflected in the longer-term planning for JET, was also described in detail. In the upcomingcampaigns significant enhancement of the JET facility, towards higher power with the ITER-like plasma shape will allow JET toperform important experiments in preparation of ITER. At the end of this year, an ITER-like ICRH Antenna is to be installed which willopen new scope for reactor-relevant research at JET. These experiments shall be followed by the installation of an ITER-like first wallscheduled for 2008 (see the June 2005 JET Bulletin).

EFDA-JET Bulletin

March 2006

JET Recent Results and Planning

Edge plasma modelling workshop at JETDuring February, EFDA-JET hosted an intensive, month-long workshop dedicated to edge plasma modelling, which was co-ordinatedby one to the JET scientific taskforces, Task Force E (Exhaust). As part of this activity, twenty physicists from across Europe andUnited States addressed a number of critical issues (power exhaust, material migration, fuel retention, etc.) related to the upcoming

JET in the Physics World

The March issue of the Institue of Physics magazine, Physics World, carries an 8 page special featureon JET. The article describes, for a general physics audience, how the research programme now, andin the future, is concentrating on critical ITER issues. An interview with ITER’s new director general,Kaname Ikeda appears in the same edition. Fusion made it to the front cover of the magazine, whichhas a circulation of about 50,000 worldwide. The article was commissioned by Physics World and hasbeen co-written by Richard Pitts, Richard Buttery and Simon Pinches, currently leaders of JET TaskForces E, S1 and M respectively. The authors would like to thank the JET EFDA contributors and inparticular the following people for their assistance in preparing this article: Vasili Kiptily, Xavier Litaudon,Paola Mantica, Jan Mlynar, Olivier Sauter, Sergei Sharapov, Tuomas Tala and Mark Woollard.

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JET experiments and to the ITER project. These included fluid-kinetic modell ing of: wall material erosion, deposition andtransport; 13C injection experiments; Edge Localised Mode (ELM)power exhaust along magnetic field lines; ELM-limiter interaction;high density divertors and photon opacity; thermal quench phase ofplasma disruptions; new ITER-like shaped JET plasmas; JET-ASDEXUpgrade comparison studies; drift wave edge plasma turbulence andedge-SOL (Scrape-Off Layer) plasma turbulence simulations of JETohmic and L-mode discharges (see figure). Significant effort was alsoplaced on code-code benchmarking, core-edge integrated modellingand improved formulations of guiding centre drifts within fluid codes.

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JET 2005 scientific Highlights

Study of ion loss during Edge Localised Modes (ELMs)The JET Retarding Field Analyser (RFA) probe (photograph) provides the first direct measurement ofion energies convected outwards to the main chamber walls by Type I ELMs. The probe - insertedusing a fast reciprocating drive into the scrape-off layer - is "bi-directional", with sensors alignedperpendicular to the magnetic field facing the inner and outer divertors (the "e-side" and "i-side" markedin the figure). During ELMs, the i-side current density (jsat) dominates, showing that the ELM ejectsparticles preferentially in the outboard midplane region. Picturing the ELM as made up of a series ofcurrent "filaments" expelled simultaneously at multipletoroidal locations then propagating radially whilst losingenergy rapidly along the magnetic field (as observed onMAST, ASDEX Upgrade and DIII-D) provides anexplanation for the structure seen in the probe detectorcurrents. The ion current measured inside the RFA (icoll)in the example shown here is due to ions which havebeen able to surmount a potential barrier of 400V. A newtransient parallel loss model of ELM energy dissipation(published this January in Plasma Physics and ControlledFusion journal) reproduces the measured i-side collectorcurrent (black line), showing that the ELM convects ionsto the walls with energies characteristic of the H-modepedestal region.

Plasma particle density profile versus collisionality in H-modesThe JET database on density peaking has been expanded with discharges dominated by radio-frequency heating. Regressionanalysis was performed on the expanded database, which, among severalother parameters, takes account of neutral beam fuelling as a particle source.The scaling obtained in this way confirms that collisionality is the most importantscaling parameter and that density profile peaking increases with decreasingcollisionality in H-modes. A significant level of density peaking is predicted forITER. The theoretical interpretation of the observed dependence of densitypeaking on collisionality is still controversial and poses a challenge to gyrokineticmodels.

Poloidal rotation in discharges with ITBFigure on the left shows a strong Internal Transport Barrier (ITB) expandingoutwards in major radius, in JET Pulse No: 61324. From t = 4.04s onwards, theITB is within view of the poloidal charge exchange diagnostic, which can measurepoloidal rotation of carbon impurities in the plasma.

In the figure on the right the poloidal rotation of carbon measured in thisdischarge is shown at two times, one (red) when the diagnostic is viewing outside the ITB, and the other (blue) when the diagnosticis viewing the plasma both outside and inside the ITB. These measurements indicate there is a significant difference between the

poloidal rotation either side of the ITB,with rotation in the enclosed region(R<3.4m) reaching much higher levels. Neoclassical theory predictscarbon poloidal rotation of a fewkm/s while the measured values arean order of magnitude larger within theITB. Theoretical and modelling workis in progress to understand the causeof this rotation, and its link to ITBs.(Published in Phys. Rev. Lett.)

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Material migration in outer divertorPrevious experiments on JET (2001) showed that carbon injected at the top of the vacuum vessel was deposited mostly on the innerdivertor. This was understood as a result of Scrape-Off Layer (SOL) flows from the outer divertor to the inner divertor, which carriedthe injected carbon with them. The observation suggested most material released from the first wall would be deposited on the innerdivertor. More recent experiments with carbon (13C) injection in the outer divertor region rather than from the top of the vacuum vesselhave shown that material migration is more complicated in thisregion. Part of the injected carbon is deposited locally onto theouter divertor tiles close to the injection point, and a significantamount is transported to the inner divertor. The injected carbon isalso found on a deposition probe on top of the machine, indicatingstrongly that it migrated up to the X point, through the confinedplasma, back into the SOL and then down to the inner divertor leg.Modelling is underway to understand how the observed migrationarises, and to improve predictions for ITER, where tritiumaccumulation by co-deposition must be strictly controlled.

In experiments with modulated IonCyclotron Resonant Frequency(ICRF) power is deposited at twolocations, at the centre (R~3m) andoff-axis (R~3.6m), in a plasma withan Internal Transport Barrier (ITB)around R~3.35m. Two heat wavesare generated and propagatetowards the ITB. The amplitude(red squares) and phase lag (bluecircles) of the resulting heat waveacross the plasma are shown. Theamplitude is damped stronglywhen it meets the ITB from eitherside. The phase rise shows that the wave slows down. This demonstrates that theITB is a narrow layer with reduced heat diffusivity and with transport propertiesconsistent with turbulence suppression. (Published in Phys. Rev. Lett.)

In experiments with off-axis NeutralBeam Injection, the radial distributionof fast injected tritium ions has beenstudied. This distribution is measured indirectly,by observing 14 MeV neutrons originating from fusion reactions between the fast tritiumions and the deuterium in the plasma. Plasmas with a high edge safety factor (q95 ~8.5) show a radial distribution of fast tritium ions in good agreement with simulationsusing the transport code TRANSP, peaking off-axis where the beams are aimed.However, at more ITER-relevant, low q95 ~ 3.3, some fast ions appear to be transportedto the plasma centre, in disagreement with simulations. This anomalous behaviourdoes not appear to be related to sawteeth or MHD. Efforts to develop an understandingare ongoing. The results of this study could be important to improve predictionsrelating to the off-axis neutral beam current drive on ITER.

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Since the start of Neutral Beam injectioninto plasma in January, operation of theupper half of the Neutral Beam system onOctant 4 has been strongly affected by thepresence of an obstruction in the vicinity ofthe Neutral Beam Duct and High VacuumRotary Valve. After an intervention toremove the foreign body from the Octant 4Neutral Beam Duct and to repair a waterleak in an Octant 8 neutraliser, JETresumed plasma operation on 3 March. Thevessel conditions are good, as shown bythe fact that an H-mode was demonstratedalready on 8 March with auxiliary heatingpower in the range of 8 ~ 10 MW, obtainedduring 5-6 second neutral beam pulsesfrom Octant 4. Vessel conditioning andcommissioning of all systems -including IonCyclotron Resonant Heating, Lower HybridCurrent Drive and diagnostics- is underway. The Experimental Campaigns areforeseen to start after Easter 2006.

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EFDA JET Close Support Unit, Culham Science Centre, Abingdon, Oxfordshire, OX14 3EA, United Kingdom.

Phone +44(0)1235 465270. Fax +44(0)1235 464415. e-mail public-relations@jet.efda.org

©J.Pamela (EFDA Associate Leader for JET) 2006. This internal bulletin or parts of it may be reproduced without permission. Text pictures and layout, except where noted, courtesy of the EFDA

Parties. The EFDA parties are the European Commission and the Associates of the European Fusion Programme which is co-ordinated and managed by the Commission. Neither the Commission,

the Associates nor anyone acting on their behalf is responsible for any damage resulting from the use of information contained in this publication.

JG05.629

Dr Umberto Guidoni MEP visited the JET facilities on Monday 6thFebruary 2006. Dr Guidoni, a former astronaut in two space shuttlemissions, had the opportunity of exchanging views on the Europeanfusion programme with Dr Jérôme Paméla (Associate Leader forJET) and Prof Sir Chris Llewellyn-Smith (Director of UKAEA Culham Division). During the visit to the Torus Hall, Dr Umberto Guidonigave an interview to Ms Emma Jane Kirby (BBC World Service) and was able to try for himself some of the remote handling tools.

MEP Jan Christian EhlerDr Jan Christian Ehler MEP and three colleagues visited theJET facilities on Thursday 8 December 2005. With a backgroundas a managing director of Biotech GmbH - the biotechnologycentre Hennigsdorf, Dr Ehler was well informed about Europeanscience policy and was particulary interested in energy researchand fusion.

New staff join EFDA JET Close Support UnitChristina Mrozek from IPP Garching joined CSU in February as the new Head of Administration following the return of CatherineSoltane to Cadarache to work for the CEA ITER administration. Remi Reiss from CEA joined the Enhancement Deparment inJanuary, and Daniela Püttman-Kneupner from FZJ reinforced the Contract Service in March. The CSU also welcomed Helen Dawsonas a new part-time finance administrator. Two students from the Netherlands, Jeroen Klijs and Joost Simkens, are currently attachedto CSU Publications to finalise their theses in fusion policy - their study focusses on the secondary benefits of fusion research.

Didcot Power Station staff tour JETOn 31st January 2006 JET hosted a visit for staff from the nearbyDidcot Power Stations, owned by RWE npower. Didcot A PowerStation is a dual-fired (coal and gas) power station, capable of

generating 2000 MW of electricity.The site also includes Didcot B, which is a combined cycle gas turbine (CCGT) power station thatcan generate up to 1360 MW of electricity. Together the power stations can supply enough electricity to some 3 million people, threetimes the size of Oxfordshire. The stations are approximately 5km from the JET site and were one of the positive factors deciding itslocation in Culham. Among other facts, our guests learned in detail about the JET remote handling system (photo) and JET powersupply units. Emma East, CommunityRelations Co-ordinator from the powerstation said: “It was very popular withour staff. Engineers are always hungryfor new information and ideas to expandtheir minds. We had such a goodresponse for the visit from our staff thatwe’re hoping to organise another visitin the near future.”.

Stavros Chatzpanagiotou gave a presentationon Joint European Undertaking for ITERMr Stavros Chatzipanagiotou, Head of the European Commission Unit for Implementationof the European Legal Entity for ITER, and colleagues Mr R Monk and Mr T Bousiosvisited the JET facilities on Wednesday 15 February 2006. Mr Stavros Chatzipanagiotououtlined the Joint European Undertaking for ITER and the Development of Fusion Energyin a presentation to staff. Related personnel needs were also discussed during hispresentation, which wasbroadcast via the Internetto over 20 different sitesaround Europe.

MEP Umberto Guidoni