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EFDA-JET Bulletin

2004 JET AnniversaryOn 20th May 2004, JET celebrated the 25th Anniversary of the laying of theJET Foundation Stone and the 20th Anniversary of the Official Opening ofJET. The JET Anniversary day was organised under the patronage of theEuropean Commissioner for Research, M. Philippe Busquin. Current andformer colleagues met to recall the early history of JET and to share theirenthusiasm in current JET research. We were very proud to welcome manydistinguished guests to JET on the Anniversary Day, including CommissionerPhilippe Busquin himself and the French Minister for Research M Françoisd’Aubert. The widespread interest in the fusion community in the JETAnniversary was also demonstrated by the presence of all the chairmen ofthe European Fusion Committees, most of the Directors of the EuropeanFusion Laboratories and several leading scientists from outside Europe, such as Dr David Baldwin from the General Atomics,Prof Miklos Porkolab, Director at MIT and the Academician Evgeny Velikhov, President of the Kurchatov Institute.

“JET is one of the most remarkable examples of a truly European research, a proof of the success that Europe canobtain when it unites its forces” said Philippe Busquin in his opening speech. A message of congratulations from UK PrimeMinister Tony Blair was then read out by the Director of UKAEA Culham Division, Professor Sir Chris Llewellyn Smith.

August 2004

I am delighted that fusionand JET have been “ahead ofthe game” in Europeancollaboration, involving many ofthe new accession states infusion research well before theiractual accession.

From the letter of UK Prime Minister Tony Blair

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All the talks, exhibition postersand letters, as well as manyimages from JET history andfrom the Anniversary day can befound on a dedicated webpage,see http://www.jet.efda.org/,under Focus On articles.

A short ceremony by the JET foundation stone followed, with a photo exhibition in the Atrium opposite the Control Room.The exhibition consisted of archive photographs showing not only the construction works, but also many personalities andevents relevant to JET history.

A special issue of the JET Bulletin, distributed on the Anniversary day, recalled all the milestones that JET achieved infusion science and engineering. All the guests were given the opportunity to visit the Torus Hall, or to learn about currentRemote Handling operations, or just to relax and meet one another at the exhibition area.

The main part of the Anniversary day started after lunch. Four invited speakers offered us a fascinating insight into theorigins of JET. Professor Donato Palumbo, former Director of Research in EURATOM, detailed the birth of the commonEuropean endeavour in fusion research. Professor François Waelbroeck, former Chairman of the Tokamak Advisory Group,presented a broad review of the fusion research evolution that anticipated JET construction. Professor Paul-Henri Rebut,leader of the JET Design Team and later the second Director of JET, summarised the conceptions and objectives of the JETfacility. Finally, Professor Francis Troyon, former Chairman of the JET Council, gave a passionate talk about JET’s scientificcontribution to the design of ITER.

The second round of the talks, opened by Dr Carlos Varandas, Chairman of the EFDA Steering Committee, weredevoted to current JET achievements and tasks. Dr Jérôme Paméla, EFDAAssociate Leader for JET, presented recent JET results, demonstrating that thecurrent JET programme is driven by its ITER relevant capabilities. To illustrate thispoint, Dr Paola Mantica, one of the new JET Task Force Leaders, detailed progressand challenges in transport studies. The talks were concluded by an overview ofexpertise achieved in operating JET, presented by Dr Frank Briscoe, UKAEA JETOperations Director.

The message of all the talks was clear: the design, results and capabilitiesof JET play a key role in the present ITER-oriented fusion research, so that there isa strong need for its further exploitation. This was very encouraging for all theaudience, in particular for former and present fusion scientists and engineers.

The celebrations continued into the evening in a less formal mood. Largemarquees with the pig roast, bar and music by the Wantage Silver Band maintained

a warm, enjoyable atmosphere even with the rain pouring down outside. It was a very special day indeed.In organising this event, EDFA JET appreciates all the organisational and moral support that we have received from

UKAEA Culham Division, the JET Operator, and in particular the efforts of many enthusiastic individuals.

A commemoration beside the JET Foundation StoneFrom L to R: French Minister of Research Mr François d'Aubert, Dr Gisela Wüster (widow of Dr Hans-Otto Wüster, the

first JET director), Research Commissioner Mr Philippe Busquin, and EFDA Associate Leader for JET Dr Jérôme Paméla.

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JET Experiments

Highlights of 2004 Campaigns

In helium plasmas, accelerating helium beam particles to severalMeV by third harmonic Ion Cyclotron Resonant Heating (ICRH)provided an invaluable technique for simulating fusion-producedα-particles, without the complications of a full-scale deuterium-tritium experimental campaign. The method is particularly beneficialin gaining insights into α-particle transport on ITER, and to testfast particle diagnostics for ITER. For example, changes in thefast ion distribution function during MHD instabilities such assawteeth or Alfvén cascades, excited by ICRH accelerated ions,were measured with X-ray imaging; slowing-down of α-particleswas tracked by a new diagnostic technique based on XUVspectroscopy; lost α-particles were detected by measuring theactivation induced in samples located near the plasma edge (firstapplication of this method in a large tokamak).

Work on Advanced Scenarios and Hybrid Scenarios (animproved H-mode regime where an edge barrier occurstogether with improved core confinement) was geared towardsexploring these regimes in more ITER-like conditions, includingplasmas dominated by Ion Cyclotron Resonant Heating. InAdvanced Scenarios, ion ITBs were produced (with establishedelectron ITBs) without external momentum injection, and ionITBs were produced with as little as 5MW of input power.ICRH-dominated Hybrid Scenarios were produced at lowerρ* with improved confinement and very mild edge behaviour.It was confirmed experimentally (using the fusion α-particlesimulation technique described above) that in Hybrid orConventional scenarios fast α-particles are better confinedthan in scenarios with deeply reversed shear. The promisingresults obtained with moderate levels of ICRH power in theserapidly advancing regimes underscore the potential for high-impact studies on JET with planned power upgrades.

After several attempts a new set of external error field coils werefinally brought into operation and tested during 2004 ExperimentalCampaigns. These coils were able to trigger Resistive Wall Modes(RWM, a plasma instability due to finite wall resistivity) by slowingdown the plasma rotation and thus reducing the stabilising effectof the wall. A clear β-scaling of the threshold for instability wasmeasured. The error field coils were also very effective in slowingdown plasma rotation, giving access to ITER-like plasmas withlow rotation and high power input, which will be studied in detailin future operation.

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Demonstration of Braking and PossibleRWM Destabilisation in Pulse No: 62366

H-mode: high confinement tokamak regime,characterised by a steep temperature gradient nearthe plasma edgeITB: Internal Transport Barrier, region in the plasma corewith low energy transport, characterized by steeppressure gradient.Reversed shear: a magnetic field configuration in whichthe pitch of the field lines varies non-monotonically withminor radiusρρρρρ*: normalized Larmor radius, radius of gyration of theplasma majority ion species in a given magnetic fielddivided by minor radius of the tokamakβββββ: ratio of the plasma kinetic pressure to the magneticfield pressure.

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Material erosion, its subsequent transport in the plasma and final co-depositionwith the plasma fuel is an important issue facing operation with the longer pulsesof next generation devices. A single ITER pulse is equivalent to half a JET year ofoperation in energy input and ~5 JET years of divertor ion fluence. The currentview that erosion occurs mainly on main chamber surfaces has been strengthenedby recent JET analysis in which campaign averaged spectroscopy, CD4 screeningexperiments, in-situ material deposition monitoring and post-mortem surfaceanalysis have been combined to estimate main wall carbon sources and innertarget divertor deposition rates which are in remarkably good agreement. Dedicated13CH4 gas injection studies and the unique use of beryllium evaporation at JEThave also shown that the majority of those impurities introduced into the mainchamber are deposited at the inner divertor targets during normal single-null loweroperation with the ion B×∇B drift directed downwards. The observation, in JET,of strong parallel flows (Mach No: 0.2-0.6) near the top of the machine directedfrom outer to inner divertor tends to support the view that impurities can beconvected preferentially towards the inner target. A campaign with reversed toroidalfield operation has demonstrated that the outer target can become an area of netdeposition - a new and unexpected observation that appears to be coupled withstagnation of the main Scrape-Off Layer flow, though this cannot yet beunambiguously linked with the material accumulation. Simulations includingclassical drifts in both the SOLPS5 and EDGE2D/Nimbus code packages areunderway in an effort to explain the observations.

Ongoing ex-situ analysis of graphite tiles from a whole series of previousJET divertors is revealing average fuel retention rates of ~3%. Encouragingly, this

is lower than estimates from the earlier JET D-T campaigns. In-situ measurements of material accumulation in remote areasindicates that this reduction may largely be due to regular operation in recent years with vertical target configurations in thegas box divertors compared with the earlier horizontal targetoperation, implying an important role for divertor geometry indetermining the extent of migration and retention.

Considerable effort has been devoted at JET towardsimproving both the experimental database and understanding ofenergy and particle transients and the resulting transport to firstwall surfaces. Energy balance across a wide range of disruptiontypes shows that fast disruptions (e.g. Vertical DisplacementEvents or density limits in ITB plasmas) tend to deposit moreenergy outside the divertor - an observation that potentiallyimproves the scope for ITER divertor material options but mayhave important consequences for the current choice of a berylliumfirst wall. High current, high input power operation at JET hasrecently produced examples of Edge Localised Modes (ELMs)with low frequency (~4 Hz), each carrying 1 MJ of plasma storedenergy. There is evidence for target ablation and strong impurityinfluxes during these events, demonstrating a unique JETcapability to explore ITER relevant erosion by ELMs.

ITER Specific Issues in Exhaust Physics at JET

Carbon 13 methane was injected from the topof JET and subsequent surface analysis bySecondary Ion Mass-Spectroscopy (SIMS)

showed that most of the deposition was in theinner divertor. Not all the carbon 13 isaccounted for which may be due to

toroidal asymmetry.

A substantial rise in radiated power is observed when theenergy drop due to giant type I ELMs in JET approach 1MJ –

this is consistent with the estimated ablation limits.

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Final Stage of Manufacture and Most of the DeliveriesExpected Before end October

The JET Enhanced Programme (JET-EP) has now entered its final phase. Apart from the new ITER-like ICRH antenna, whichwill be installed in two steps, all the new and refurbished systems have to be installed by the end of the current shutdown,that started in March this year and ends in February next year.

All the systems are now in the final stage of manufacturing andJET is facing a very delicate period where the delivery deadlines

become ever closer andtherefore all last minutediff icult ies have to beresolved very efficiently.The delivery histogrampresented to the rightshows how critical thissummer period is regardingdeliveries.

After several modifi-cations, the shutdown planhas been finalised, and theobjective we have ofinstalling about fifteen newsystems is extremelychallenging. Let us give here a few examples of items already delivered or veryclose to be shipped to JET.

• The polychromators used for the new High Resolution Thomson Scattering have arrived from General Atomics in the USand are being tested in the laboratory.

• The powerful 20 Hz laser has been built by Quantel in France and final tests at the company are being performed beforeshipment.

• The horizontal camera for the new bolometry system (KB5) was delivered to JET from PINK Vakuumtechnik, Germany, inJune. This is the first diagnostic purchased under Article 7.

• Five CCD cameras built by XCam were delivered to JET end of July and are currently being tested before final acceptance.These cameras will be used for the new Charge Exchange and Edged Current Profile spectroscopic measurements.

Every effort is being made both by the Associations involved in the projects and the companies in charge of manufacturingthe instruments to achieve the very tight delivery dates in order to be ready for the restart in March 2005.

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Total DeliveriesVac BoundaryIn-VesselEx-VesselOutside Torus Hall

20Hz laser in test at Quantel before delivery.

Detail of the bolometer heads of the KB5 horizontal camera.Whole KB5 horizontal camera

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New Task Force Leaders for JET

JET Experiments

JET Experimental Campaigns in 2005

In 2005 major enhancements to the JET Facilities will be exploited to progress a set of high priority ITER activities. Campaigntime will be dedicated to four Headline areas.

• The first Headline, with the highest priority, involves bringing the new systems (divertor and diagnostics) and the LowerHybrid launcher to full performance.

• The second Headline involves study of critical issues for ITER, which could influence the detailed design of ITER components,such as the first wall, heating & current drive systems and diagnostics. Much of this effort will concentrate on achievingmild edge behaviour in ITER-relevant scenarios, and on improving the understanding and characterisation of disruptionsand fast particle losses.

• The third Headline involves preparation of ITER operating scenarios, with the aim of optimising the start-up of ITER. Thehigher triangularity afforded by the new divertor will be used to study and optimise the ELMy H-mode in a more ITER-likeregime, and control schemes for the steady-state and hybrid scenarios will be progressed.

• Under the fourth Headline specific ITER physics issues will be addressed, where JET offers unique insights, for example,in transport and burning plasma physics.

These experiments will be conducted in three Campaigns beginning mid-2005 and extending over 4 months with a total ofabout 81 planned S/T days.

On 26th June 2004, the EFDA Steering committee approved the following Task Force Leaders (TFLs) and their Deputiesfor the JET 2005 experimental campaigns:

The renewal of the EFDA JET Close Support Unit also continues: Ms Linda McWhirter joined us in January as PersonalAssistant to EFDA Associate Leader for JET / Head of CSU Dr Jérôme Paméla, and Dr Francis Sabathier reinforced theEnhancement group in August.

Task Task Force Leaders TFL DeputiesForce

S1 Dr G Sips, IPP Garching Dr R J Buttery, UKAEA-CulhamDr T Loarer, CEA-Cadarache

S2 Dr X Litaudon, CEA-Cadarache Dr C D Challis, UKAEA CulhamDr F Crisanti, ENEA-Frascati

M Dr D Borba, IST-Lisbon Dr S J Pinches, IPP-GarchingDr H R Koslowski, FZJ

E Dr R A Pitts, CRPP-Lausanne Dr W Fundamenski, UKAEA-CulhamDr V Philipps, FZJ

H Dr J Ongena, ERM/KMS-Bruxelles Dr J Mailloux, UKAEA-CulhamT Dr P Mantica, CNR-Milano Dr V Naulin, Risø

Dr T J Tala, TEKESD Dr A Murari, RFX-Padova Dr E de la Luna, CIEMAT-Madrid

Dr J Brzozowski, VRFT Dr C J Grisolia, CEA-Cadarache Dr P Coad, UKAEA-CulhamDT Dr K Zastrow, UKAEA-Culham

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Publications at JET have been always of major importance as the success of the scientific work is primarily judged by thenumber and the quality of published papers. This perception is the reason for setting up a clearance process for all ourpublications, a template for posters and rehearsals of all oral contributions to conferences.

The normal channel for publication of work originating at JET isby means of conventional scientific literature (i.e. Scientific Journals,Books, and similar publications) or by presentations at InternationalConferences and Meetings. From the beginning of EFDA JET inJanuary 2000 until now (July 2004) about 1072 contributions toconferences and 250 papers to journals have been placed on ourpinboard system. These figures, with an average of 50 articlespublished in journals and more than 200 contributions to conferencesper year, show the essential role played by JET in the fusion community.

Outside normal channels of publication, these papers graded“Unclassified - Approved for publication”, are given electronic advanceddistribution as pre-publication editions in the JET Preprints website at

http://www.iop.org/jet/. These web pages constitute the most complete central repository of JET publications and feature asearch facility for fast document retrieval and hyperlinks on each figure linking to diagrams in our “Figures” central archive.

All the JET preprints are loaded onto the IoP website after havingcompleted an internal clearance procedure. The process of clearance forJET publications, now fully electronic, has always been thought necessaryto ensure a uniform standard for the dissemination of information. At thesame time, it brings the benefit of ensuring that each paper passes througha minimum process of peer review before being made available to thepublic.

The starting point of the clearance process is the pinboard. Thepinboard pages, open to all registered users, are intended to allow peopleto review all the contributions before they are presented or published. Placinga document on the pinboard initiates the clearance procedure. In particular,the pinboard automatically submits an electronic clearance form to thePublications Officer. The clearance requires at least two signatures: one fromthe relevant Task Force Leader and the other from the EFDA Associate Leader. These individuals are requested to make commentsin order to ensure the overall scientific coherence of all publications and the appropriateness of authorship.

Having obtained clearance, the authors are requested by JET’s Reprographics Office to supply all figures in electronicform. These figures are stored in an EPS format and archived toa central database. Each diagram and viewgraph carry a uniquereference number (for example JG01.246-14c) placed on thelower right hand side.

All cleared papers are formatted into a house style and storedin a PDF format. These are submitted to the JET Preprint &Conference Paper Archive held at the IoP. All diagrams containedwithin the PDF file are hyperlinked back to the figures webserver(see box to the left) and deliver an EPS version direct to the user.

From the preprint website to the figures webserver, the wholepublication area has evolved in recent years in such a way as tomake these tools essential for the scientific work at JET.

Publications at JET

A figures web server is available athttp://figures.jet.efda.org/. It allows any user toretrieve a figure from the JET archive fromanywhere on the internet. A search for a figurecan be made either by reference number or bykeyword. Figures are available for download ineither EPS format (Encapsulated Postscript) or JPGformat. Use of the figures is subject to copyrightrules.

Nuclear Fusion

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Articles on JET Pinboard to be Published on Journals(2000-July 2004)

Contributions to Conferences on JET Pinboard(2000 - July 2004)

Page 8EFDA JET Close Support Unit, Culham Science Centre, Abingdon, Oxfordshire, OX14 3EA, United Kingdom.

Phone +44(0)1235 465370. Fax +44(0)1235 464800. e-mail public-relations@jet.efda.org

J.Pamela (EFDA Associate Leader for JET) 2004. 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.

JET Events

January 19 JET entered C13 campaign (deuteriumplasmas with D or He beams)

January 22 NBI achieved record injected power22.7MW on pulse 62620

February 3 The number of visiting scientists at JETpeaks at one hundred

February 9 JET entered C14 campaign (helium orhydrogen plasmas and beams)

February 20 Visit of James Elles, MEP

March 5 End of C14 campaign. Ten-month periodof shutdown commences

April 1-2 EFDA JET neutron diagnostic workshop

April 27 The Remote Handling Boom entered thevacuum vessel for the first time sincethe end of Operations

April 28-29 EFDA JET hosts the EIROforumworkshop on neutron diagnostics

May 4-5 EIROforum Assembly meets at CulhamScience Centre

May 7 Swiss Secretary of State for Research,Dr Charles Kleiber, visited JET

May 20 JET Anniversary day (see the article)

May 21 First wall photon cleaning experiments usingRemote Handling

May 26 EFDA JET workshop on Reflectometry –Present status and future prospects

June 21 New Vertical Bolometer camera was delivered

June 26 Task Force Leaders for the JET 2005Campaigns approved (see the article)

June 23 Visit of Chinese Ambassador Mr Zha Peixin

June 29 The JET Facilities welcome participants of the31st EPS Conference on Controlled Fusionand Plasma Physics, London

July 1 Polychromators for the new High ResolutionThomson Scattering System arrived from theGeneral Atomics, US

July 22 Five cameras for the new Charge exchangeand Edge current spectroscopy delivered

The JET Remote Handling group is carrying out close to 200 tasks of remote in-vessel maintenance and enhancementsduring the current shutdown. The works continue apace as the group moved to the second phase earlier this summer,marking the start of the more challenging remote in-vessel tasks.

Phase one was about preparation. Preparing for removal of installed components, cleaning tile surfaces, surveying in-vessel areas where new components are to be installed and carrying out some investigative work where minor damage andgeneral wear n’ tear occurred as a result of operations. One ofthe more unusual remote tasks in phase one was the PhotonicCleaning of Tile Surfaces by a flash lamp for tile detritiationpurposes. The cleaning was carried out on a divertor tile carrierand a section of poloidal limiter tiles. This work is related directlyto ITER so that the results will be no doubt viewed with interestby our friends in Garching.

After a short manual intervention, remote phase twoimmediately turns up the heat, quite literally, with the start ofwhat is to be a significant amount of remote welding, challengingboth equipment and the skills of the remote handling team.

Looking forward, phase two includes removal of the majorityof tile carriers and the start of what will be the first of several majorinstallations involving new diagnostic systems.

Stephen Sanders On contract from Oxford Technologies Ltd.

The JET Shutdown - A Remote Handling Perspective