Introduction to Fusion Research atJET

JET–R(99)14

E.R. Solano, J. Jacquinot et al

“This document is intended for publication in the open literature. It is madeavailable on the understanding that it may not be further circulated and extractsmay not be published prior to publication of the original, without the consent ofthe Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA,UK”.

“Enquiries about Copyright and reproduction should be addressed to thePublications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA”.

JG00.106/1

Introduction toFusion Research

at JET

Information from the JET team and collaborators,compiled by. E. R. Solano and J. Jacquinot.

Special thanks to the following JET team members:

B. Alper, M.N.A. Beurskens, C. Challis, A. Chankin, J. Christiansen,S. Clement, P. Coad, S. Cox, G. Conway, G. Cordey, G. Cottrell,C. Giroud, J. van Gorkom, C. Gormezano, C. Gowers, H. Guo,N. Hawkes, L. Horton, C. Ingesson, T. Jones, M. Keilhacker, P. Lomas,G. Matthews, F. Milani, F. Nave, F. Rimini, G. Saibene, Y. Sarazin,R. Sartori, A. Sips, D. Stork, P. Thomas, M. Watkins, J. Wesson,K.-D. Zastrov, M. Zerbini

and collaborators:S. Cowley (UCLA), G. Hammet (PPPL), K. Lackner (MPI-IPP), C. Petty(GA), F. Porcelli (P. Torino), P. Stangeby (U. Toronto).

JG00.106/105

From time to time, fusion researchers are called upon to give a talk aboutfusion or tokamaks to an audience of non-specialists.

The set of transparencies that form this report was made and collected tofacilitate that task. Some basic concepts are explained, defined and illustrated.Where examples or illustrations are called for, relevant JET results arepresented. The authors are indebted to the JET team researchers andcollaborators for information, ideas and material.

The report has the following “chapters”:

Fusion, Energy… …………………………………………………………… 2energy issues

JET Project & Device ……………………………………………………… 10objectives of JET, administrative structure of the JET Joint Undertaking, the JETProgramme (1983-1999),

Introduction to Fusion Physics (Basic) ……………………………...…….. 28fusion reactions, plasmas, Q, orbits, tokamak fields, stability, turbulence, confinement

PEP mode, Snakes, Monster Sawteeth ……………………………………. 50phenomena observed experimentally in JET, leading to fruitful research..

Scaling Laws ………………………………………………………………... 55wind-tunnel, dimensionless scaling, extrapolation,

Internal Transport Barriers ………………………………………………. 63confinement bifurcation, profiles, turbulence

Fusion in JET ……………………………………………………………….. 70results from DT campaigns, isotope effect, performance, alphas

Divertors ……………………………………………………………………. 77what for, how, history of JET divertors, erosion/deposition, divertor physics

Technology and Diagnostics ………………………………………………. 88remote handling, overview of diagnostics, specific examples: LIDAR TS, MSE, CXS,ECE, Reflectometry

This report should not be quoted as a reference in scientific publications: the originalsources of information should be sought and quoted instead.

JG00.106/1

JG00.106/2

Fusion, Energy

JG00.106/3

Fusion – Main issues

Heating• Ohmic• Neutral Beam Injection• Ion Cyclotron Resonance• Lower Hybrid systems• α particle heating 350 Million °C

ContainmentTokamak (Toroidal device)

• Particle orbits• MHD instabilities• Micro-instabilities Anomalous transport• Scaling laws• Bifurcations

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Impurities• Heat and particle exhaust• Plasma surface interactionsEdge and divertor physics

JG00.106/4

How can Fusion helpour Energy needs?

1500

1000

500

01860 1900 1920 1960 2020 2060

Shell Oil company scenario for sustainablegrowth in 2060

Exa

joul

es

JG99.47/2c

Unknown!Geothermal

Solar

Biomass

Wind

NuclearHydro

Fossil fuels &traditionalbiomass

JG00.106/5

Fusion Energy – Advantages

• Fusion fuels have very large energy density:

– 1 gram of fully reacted Deuterium-Tritium fuelgives around about 26000 kW·hr of electricity ,enough for about 5000 households for 1 day.

– 1 gram of fully burnt Coal gives only about3W.hr of electricity (ie 10 million times less)

• Fusion fuels are abundant and geographicallywidespread:

– Deuterium (extracted from sea water), enough for300 thousand million years

– Tritium is made from Lithium using a fusionreaction.

– Lithium (abundant on land and in the oceans),enough for about 2000 years

JG00.106/6

Fusion Energy – Advantages(continued)

• Fusion fuels are ‘clean’:

– Fusion does not give rise to Greenhouse gases (CO2) orAcid rain gases (SO2, NO2)

• Fusion reactors are inherently safe:

– A very small quantity of fuel is kept in the reactor region(only enough for a few tens of seconds operation)

– ‘Critical’ or ‘meltdown’ situations associated with NuclearFission are physically impossible

– Accidents are self limiting and Public evacuation wouldnot be necessary

JG00.106/7

Fusion Energy – Advantages(continued)

• Fusion fuels are not involved in nuclear proliferationproblems:

– No plutonium

– Tritium remains on site in the fuel cycle

• Fusion reactors leave no long lived highly radioactivewaste:

– No long-lived radioactive waste from the fuel cycle

– After around 100 years the Fusion reactor using selectedmaterials would only leave low level radio-active structuralcomponents

JG00.106/8

No Long-lived Radioactivityafter Shutdown

‘Fusion Model 1’ : advanced materials (Vanadium alloys)requires development

‘Fusion Model 2’ : Low activation Stainless Steel/ watercooled

Near-term technology

0 50 100 150 200 250 300 350 400 450 500Time after shutdown (years)

1

101

102

103

104

105

106

107

108EFR A

EFR B

PWR

Coal

FusionModel 1

FusionModel 2

Comparison of Relative Radiotoxicityfrom various power sources

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Rel

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oxic

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JG00.106/9

Fusion Energy– Disadvantages

• Fusion reaction is difficult to start!

High temperatures (Millions of degrees) in a pure HighVacuum environment are required

Technically complex and high capital cost reactorsare necessary

• More Research and Development is needed to bringconcept to fruition

The physics is well advanced but requires sustaineddevelopment on a long time scale (20 to 40 years)

JG00.106/10

JET Project&

Device

JG00.106/11

Fusion research:Science and Energy

Research is mission-driven.

JET has a clearly defined objective:

“to obtain and study a plasma in conditions anddimensions approaching those needed in a

thermonuclear reactor. These studies will be aimed atdefining the parameters, the size and the working

conditions of a Tokamak reactor.”

This requires work in four main areas:

(i) The study of scaling of plasma behavior as parametersapproach the reactor range;

(ii) The study of plasma-wall interaction in these conditions;

(iii) The study of plasma heating;

(iv) The study of alpha-particle production, confinement and consequent plasma heating.

JG00.106/12

JET

• A European project “to obtain and study plasmas inconditions and dimensions approaching those needed ina reactor. These Studies will be aimed at defining theparameters, the size and the working conditions of aTokamak reactor .”

• In practice:

– Size adequate to confine α particles →

– 30 MW of heating (several methods)

– Flexibility in:

– Plasma topology

– Heat and particle exhaust.

• Members: the European Commission and all the EU countries(+ Switzerland) working in fusion

• Budget ~ 70 million Euros

• Operated since 1983

Ip > 3MA

R > 3m~

~

JG00.106/13

Objectives of JETThe essential objective of JET, set originally (1975), is:

“to obtain and study a plasma in conditions and dimensionsapproaching those needed in a thermonuclaer reactor. Thesestudies will be aimed at defining the parameters, the size and

the working conditions of a Tokamak reactor.”

This requires work in four main areas:(i) The study of scaling of plasma behaviour as

parameters approach the reactor range;(ii) The study of plasma-wall interaction in these conditions;(iii) The study of plasma heating;(iv) The study of alpha-particle production, confinement

and consequent plasma heating.

Objective of New Phase (1992-1996) is to establish in deuterium:“reliable methods of plasma purity control under conditions

relevant for the Next Step Tokamak”

Purpose of the present programme (to end–1999) is:“to provide further data of relevance to ITER”

• In particular, to:(i) make essential contributions to the development and

demonstration of a viable divertor concept for ITER ,(ii) carry out experiments using deuterium-tritium plasmas

in an ITER-like configuration ;while allowing key ITER-relevant technology activities ,such as the demonstration of remote handling and tritiumhandling, to be carried out.

JG00.106/14

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JG00.106/15

Composition of JET Teamby Nationality in 1998

UK 208

Germany 12

Italy 11

The Netherlands 5

Denmark 5

Sweden 1

Switzerland 2

Ireland 4

Belgium 1

Greece 1

Austria 1

Others 5France 8

JG99

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UK 191

JG00.106/16

Composition of JET Team (by Nationality),plus Contractors, in 1990: 657

Sweden 8Belgium 6

Switzerland 6

Greece 4

Others 6

Luxembourg 1Netherlands 16

Denmark 10

Ireland 22

France 42

Italy 34Germany 30

UK 249

Contractors 222

Spain 1

JG00

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Composition of JET Teamplus contractors (by Nationality)

in 1990: 657

JG00.106/17

JG00

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180

160

140

120

100

80

60

40

20

0

1977

1979

1981

1983

1985

1987

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1999

2001

InvestmentsStaff CostsOperationg CostsA+CSUJOC

Annual Phasing of JET Costs(Commitments) in 1997 MioECU

JG00.106/18

MEMBER % Mio ECU

EURATOM 80.0000 60.61

BELGIUM 0.1817 0.14

CIEMAT, SPAIN 0.4186 0.32

CEA, FRANCE 1.8581 1.41

ENEA, ITALY 1.8395 1.39

RISO, DENMARK 0.0827 0.06

LUXEMBOURG 0.0037 0.00

ICCTI, PORTUGAL 0.0970 0.07

DCU, IRELAND 0.0378 0.03

KFA, GERMANY 0.5388 0.41

IPP, GERMANY 2.4385 1.85

FZK, GERMANY 0.7578 0.57

NFR, SWEDEN 0.2299 0.17

SWITZERLAND 0.4978 0.38

FOM, NETHERLANDS 0.3158 0.24

TEKES, FINLAND 0.0895 0.07

UKAEA 10.5921 8.02

ÖAW, AUSTRIA 0.0207 0.02

100.0000 75.76

Percentage Contributions to JET for 1998,based on the Euratom participation in

Associations’ Contracts for 1998

JG00.106/19

COUNCIL

ChairmanF. Troyon

ChairmanG. Leman

ChairmanK. Lackner

DIRECTOR

J. Jacquinot

Associate Director,Head of Administration

Department

Associate Director,Head of Heating and

Operations Department

Deputy Director,Head of Torus and

Measurements Department

EXECUTIVE COMMITTEE SCIENTIFIC COUNCIL

JG99.253/1c

JET: Overall ProjectStructure

JG00.106/20

JET: Overall ProjectStructure

COUNCIL

ChairmanF. Troyon (Switzerland)

ChairmanG. Leman (Sweden)

ChairmanK. Lackner (Germany)

DIRECTOR

J. Jacquinot

EXECUTIVE COMMITTEE SCIENTIFIC COUNCIL

JG99.253/3c

JG00.106/21

Dissemination of JET Information

• JET encourages staff to publish.– Official permission must first be obtained.– Approval required for all publications, eg books, journal

articles, reports, letters, lectures, broadcasts, etc.

• Approval procedure intended to ensure that:– Consistent data and results are presented and that proper

attributions and acknowledgements are made to relevantcontributors;

– Information is released in properly regulated manner (inkeeping with Euratom and JET Statutes);

– High standards (particularly, on quality) are maintainedfrom the Project;

– Proper records are maintained throughout the history ofthe Project.

To obtain approval for dissemination of JET information,the text of the article should be attached to

Form JCA1 (Rev 7/84).

• The series of Reports is as follows:– EUR-JET-R (JET Report Series);– JET-P (JET Preprint Series);– JET-IR (JET Internal Report Series);– JET-TN (JET Technical Notes);– JET-DN (JET Divisional Notes);

JG00.106/22

Criteria for Authorship of JETPublications

(A) An author must have made a substantial contribution toa major part of the work reported and be in a position todefend (to a specialist in the subject) the detailed scientificand technological content relating specifically to his/hercontribution;

and

(B) the author must be in a position, generally, to take apersonal share of responsibility for the overall contentand accuracy of all scientific and technological informationcontained in the document.

JG00.106/23

At October, 1998

1. UKAEA, Harwell, Didcot, Oxon, UK.2. University of Leicester, Leicester, UK.3. TRINITI, Troitsk, Moscow, Russia.4. KFA, Jülich, Germany.5. Helsinki University of Technology, Espoo, Finland.6. Institute of Plasma Physics, Hefei, P R of China.7. UKAEA Culham Laboratory, Abingdon, Oxon, UK.8. A.F. Ioffe Institute, St. Petersburg, Russia.9. Institute of Theoretical Physics, University of Oxford,

UK.10. ENEA, CRE Frascati, Roma, Italy.11. Royal Institute of Technology, Stockholm, Sweden.12. Imperial College, University of London, UK.13. Max Planck Institut für Plasmaphysik, Garching,

Germany.

14. Princeton Plasma Physics Laboratory, Princeton, USA.15. FOM Instituut voor Plasmafysica, Nieuwegein, The

Netherlands.16. Dept. of Neutron Research, Uppsala University,

Sweden.17. University of Saskatchewan, Saskatoon, Canada.18. University of Manchester Institute of Science and

Technology, Manchester, UK.19. IST, Centro de Fuseo Nuclear, Lisbon, Portugal.20. Institute for Aerospace Studies, University of Toronto,

Canada.21. CEA, Cadarache, France.22. University of Lund, Sweden.23. CRPP-EPFL, Lausanne, Switzerland24. General Atomics, San Diego, USA..

THE JET TEAMJET Joint Undertaking, Abingdon, Oxon, OX14 3EA, U.K.

J.M. Adams 1, P. Ageladarakis, B. Alper, H. Altmann, S. Arshad, P. Andrew, Y. Andrew 12, D. Bailey,

N. Bainbridge, B.Balet, Y. Baranov8, P. Barker, R. Barnsley2, M. Baronian, D.V. Bartlett, A.C. Bell, E. Bertolini, C. Bevil, V. Bhatnagar,

A.J. Bickley, H. Bindslev, K. Blackler, D. Bond, T. Bonicelli, D. Borba19, P. Brennan, W.J. Brewerton, M. Brix4, M.L. Browne, T. Budd,

R. Budny14, T. Businaro, M. Buzio, C. Caldwell-Nichols, D. Campling, P. Card, C.D. Challis, A.V. Chankin, D. Chiron, J. Christiansen,

D. Ciric, H.E. Clarke, S. Clement, J.P. Coad, I. Coffey7, S. Conroy16, G. Conway, S. Cooper, J.G. Cordey, G. Corrigan, G. Cottrell,

S.J. Cox, R. Cusack, N. Davies, S.J. Davies, J.J. Davis, M. de Benedetti, H. de Esch, N. Deliyanakis, A. Dines, J. Dobbing, N. Dolgetta,

S.E. Dorling, P.G. Doyle, H. Duquenoy, A.M. Edwards7, A.W. Edwards, J. Egedal, T. Elevant11, C.G. Elsmore, S.K. Erents7, G. Ericsson16,

L.G. Eriksson, H. Falter, J.W. Farthing, M. Fichtmüller, G. Fishpool, K. Fullard, M. Gadeberg, L. Galbiati, R. Garbil, E. Gauthier21,

R.D. Gill, D. Godden, A. Gondhalekar, A. Goodyear, C. Gormezano, C. Gowers, F.S. Griph, M. Groth18, K. Guenther, H. Guo,

A. Haigh, B. Haist4, C.J. Hancock, P.J. Harbour, J.D.W. Harling, N.C. Hawkes7, N.P. Hawkes1, J.L. Hemmerich, O.N. Hemming,

T. Hender7, C.H.A. Hogben, L. Horton, M. Huart, G. Huysmans, C. Ingesson15, B. Ingram, M. Irving, J. Jacquinot, H. Jaeckel,

J.F. Jaeger, O.N. Jarvis, M. Johnson, E.M. Jones, T.T.C. Jones, F. Junique, C. Jupen22, A. Kaye, B.E. Keen, M. Keilhacker, W. Kerner,

N.G. Kidd, S. Knipe, R. Konig, J.G. Krom, P. Kupschus, R. La Haye24, J.R. Last, K. Lawson7, M. Lennholm, J. Lingertat, X. Litaudon21,

T. Loarer, P.J. Lomas, M. Loughlin, C. Lowry, R.M.A. Lucock, A.C. Maas15, B. Macklin, C.F. Maggi, M. Mantsinen5, V. Marchese,

F. Marcus, J. Mart, D. Martin, G. Matthews, H. McBryan, G. McCracken, P.A. McCullen, A. Meigs, R. Middleton, P. Miele, F. Milani,

J. Mills, R. Mohanti, R. Monk, P. Morgan, G. Murphy, F. Nave19, G. Newbert, P. Nielsen, P. Noll, W. Obert, D. O’Brien, M. O’Mullane,

E. Oord, R. Ostrom, S. Papastergiou, V.V. Parail, W. Parsons, B. Patel, A. Paynter, A. Perevezentsev, A. Peacock, R.J.H. Pearce,

M.A. Pick, J. Plancoulaine, O. Pogutse, R. Prentice, S. Puppin, G. Radford9, M. Rainford, V. Riccardo, F. Rimini, F. Rochard21,

A. Rolfe, A. Rossi, G. Sadler, G. Saibene, A. Santagiustina, R. Sartori, R. Saunders, O. Sauter23, V. Schmidt, B. Schunke, S.M. Scott,

S. Sharapov, A. Sibley, M. Simon, R. Simonini, A.C.C. Sips, P. Smeulders, P. Smith, R. Smith, F. Söldner, J. Spence,

E. Springmann, R. Stagg, M. Stamp, P. Stangeby20, D.F. Start, D. Stork, P.E. Stott, J.D. Strachan14, B.C. Stratton14, P. Stubberfield,

D. Summers, L. Svensson, P. Svensson, M. Tabellini, J. Tait, A. Tanga, A. Taroni, C. Terella, J.M. Todd, P.R. Thomas, K. Thomsen,

B. Tubbing, P. Twyman, P. van Belle, G.C. Vlases, M. von Hellermann, T. Wade, R. Walton, D. Ward, M.L. Watkins, N. Watkins1,

M.J. Watson, M.R. Wheatley, A. Whitehurst, D. Wilson, H.R. Wilson7, T. Winkel, D. Young, I.D. Young, Q. Yu6, K-D. Zastrow,

W. Zwingmann.

PERMANENT ADDRESSES

At October,1998

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Phas

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1991

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use

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T F

acili

ties

afte

r 19

99)

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acte

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Phas

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ITER

Sup

port

Prog

ram

me

ITER

–Spe

cific

Dive

rtor

Stud

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ITER

Phy

sics S

tudies

Confi

neme

nt an

d Fue

lling

Stud

ies, p

ossib

ly inc

luding

Trac

e Triti

um; P

rofile

Contr

ol St

udies

PTE

DTE

1

Pum

ped

Dive

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(Mar

k I)

Dive

rtor M

odific

atio

ns (M

ark

IIA)

Dive

rtor M

odific

atio

ns(M

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usin

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D–D

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D–T

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um E

xper

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≤2.

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JG00.106/25

Requirements for JET Site

1) Technical suitability– High demand for electrical power– Ability to handle small amounts of tritium– ability to dispose of radioactive portions of JET device as

needed– Expertise and facilities for safe working in radioactive

conditions

2) Buildings and Services– General-purpose ans specially designed buildings– Support services (Workshops, computing facilities,

medical and catering services etc.)– Road, Rail and Air transport– Possibility of expansion within site

3) Social aspects– Ample living accommodation– Good shopping other amenities– Appropriate school facilities

JG00.106/26

JET

JET is a Tokamak with:

– Torus radius 3.1m

– Vacuum vessel 3.96m high x 2.4m wide

– Plasma volume 80m3 – 100m3

– Plasma current up to 6MA

– Main confining field up to 4 Tesla

JG00.106/27

Key aspects developed at JET

• Diagnostics - Lidar and 70 other diagnostics

• Heating and current drive (total ~ 35 MW)– Neutral Beam Injector 80 to 140 KeV– Ion Cyclotron Resonance 25 to 55 MHz– Lower Hybrid Systems 3.7 GHz

• Confinement– MHD stability limits– Bifurcations to different states– Scaling laws, energy and particle transport

• α particle heating (D/T experiments)

• Particle and power exhaust– Divertors (4 versions!)

• Key fusion technologies– Remote handling– Active gas handling (tritium components)

JG00.106/28

IntroductionFusion Physics

(Basic)

JG00.106/29

Magnetic Fusion

• Needs for additional energy resources in the 21st Century -Fusion energy and the environment

• Maintain a plasma at 200 million degrees (20 keV) and apressure of 1 to 2 atmospheres with energy confinement time(τ) of 2 to 4 seconds.

– Self heating by D-T fusion born α-particles⇒ energy gain .

• Plasmas, the 4th state of matter, are dominated by collectiveeffects and non-linear behaviour.

– Anomalous transport– Self organisation resulting in bifurcations

⇒ Research on fusion grade plasma is essential

Theory - Code modelling - Experimental flair

Control - Instrumentation - Materials - High Power Technology -

Mechanics... and Large Installations (τ~ a2)

JG00.106/30

Contemporary Physics Education Project (CPEP)

Plasma:The fourth state of matter

Most matter in the universe is in plasma state

JG00.106/31

Physics domains inMagnetic Fusion

• Particle orbits → confinement devices

– Toroidal devices

Tokamak (internal current)

Stellarators (no internal current)

• MHD

– stability vs large scale perturbation

– Operating domain

– pressure limits

– low q limit

• Micro-instability

– small scale turbulence → anomalous transport– bifurcations → improved confinement

• Edge and divertor physics

– Heat and particle exhaust

– Plasma surface interactions

JG00.106/32

Fusion Reactions

D + D → T (1.0MeV) + p (3.0MeV)

D + D → He3 (1.0MeV) + n (2.4MeV)

D + T → He4 (3.5MeV) + n (14.1MeV) easiest

D + He3 → He4 (3.7MeV) + p (14.7MeV)

Cross-sections for fusion reactions

10–27

10–28

10–29

10–30

10–31

10–32

σ (m

2 )

1 10 100 1000

Deuteron energy (keV)

D–T

D–D

D–He3

JG96

.48/

2c

JG00.106/33

Q, the fusion gain factor

Power density from D-T fusion

Pfusion = n2 < σ v > Efusion

Pα ~

• Energy loss from plasma core: by thermal conduction

Define energy confinement time τE: Ploss =

For steady state , Ploss = Pexternal + Pα

• Q = = is the fusion gain factor

• Q = 1 ⇒ 20% of plasma heating by fusion α’s

• Q = ∞: ignition (no external heating applied)

• For energy production, Q≥10 is adequate

3nTτE

Pfusion

5

14

Pfus

Pheat

5PαPexternal

JG00.106/34

Fusion triple product

• The fusion amplification factor, Q is related to the triple product,nτETi

Q = ~= nτE nTτE

n2 <σv> Efusion

3nT/τE

<σv>

T

Reactorconditions

Ignition

QDT=1

QDT=0.1

JETJETDIII-D

JETJET

JETJET

JT-60U

JT-60

JT–60UTFTR

TFTR

TFTR

TFTRTFTR

FTTFTR

TEXTOR

TFRTFR

DIII-D

DIII-D

DIII-D

ALC-A

ALC-C

ASDEX

PLTPLT

T10

T3D–T Exp

Reactor–relevantconditions

Inaccessibleregion

Lim

it of

Bre

mss

trahl

ung

01 10 100 1000

Central Ion temperature Ti (M°C)

0.001

01

10

100

1000

1997

1980

1970

1965

Year

JG95.113/8c

Fus

ion

prod

uct,

n iτ E

. Ti (

x102

0 m

–3 s

.M°C

)

JG00.106/35

Particle Orbits, I

In a uniform magnetic field, cyclotron motion:

Larmor radius ρL = and guiding center drifts

Implications:• adiabatic invariant µ = mv⊥

2/B• Perpendicular collisional transport has step size ρL

Dclassical = ρL2 νCoulomb

• Particles stream freely along field lines“close” field lines to magnetically confine orbits.

+

B

JG99.342/2c

+

JG99.321/5c

Btoroidal

mv⊥

eB

JG00.106/36

Particle Orbits, II• In a toroidal magnetic field Fermi drifts are present (∇B and

curvature drifts)

Neutral plasma: drift cannot be corrected with E field.

• In fact, charge separation from v∇B leads to loss of confinement,

via the E x B drift:

A solution is to add a poloidal field.

Bpoloidal created by Ip,a toroidal currentflowing in the plasmaitself.

∇B

JG99.342/3c

Bv∇B = µ B x ∇B

B±|e|B

∇B

JG99.342/4c

B

E vE x B = B2

E x B

JG99.321/6c

B

BIp

→

→

→ →

JG00.106/37

The Tokamak: Fields

Bpol~Btor/10

• Nested closed flux surfaces : p, n, T, Φ constant on flux surfaces,because of fast streaming //B, slow diffusive transport ⊥B

• Helically twisted B field lines are needed for particle confinement,force balance and stability.

circuitpoloidal1circuitstoroidal#

q = = safety factor ~ p

t

RB

aB

Stability also depends on magnetic shear , drdq

rq=s

Typical j current density, q profiles:

qaxis<1: sawteeth

qedge<2: Disruptions!

Rationals!

JG99.321/10c

JG99.321/9c

j(r)/jo q(r)1 3

2

1

00

→

JG00.106/38

Schematic ofTokamak

Iron transformercore

Toroidalfield coils

Poloidalmagnetic

field

Toroidalmagnetic

field

Resultanthelical field

(twist exaggerated)

Transformer winding(primary circuit)

Plasma current(secondary circuit)

JG95

.113

/7c

JG00.106/39

mv⊥eBpol

The Tokamak: Orbits

Poloidal Larmor radius: ρpol =

Neoclassical diffusion:

Dneocl = ρpol2 νCoulomb~100 x Dclassical

Ion transport can be near neoclassical, but typical electrontransport is 10–100 x larger than neoclassical.

2

1

0

-1

-2

R (m)43

Pulse No: 48227

2

Z (

m)

JG99

.329

/4c

RFprobe

ICRHResonance

Banana orbit (3MeV)

JG00.106/40

Fluids: MHD

Because of the long range of the Coulomb interaction, singleparticle orbits are only part of the story.

In fact the plasma can be modeled as a fluid (or a set ofinterpenetrating fluids).

The combination of fluid and Maxwell’s equations lead toMagnetohydrodynamics (MHD).

From the point of view of MHD, the concept of β becomesimportant (Raleigh-Taylor instabilities):

Linear, ideal MHD is rather well understood: plasma equilibriumcan be established in tokamaks and gross instabilities can beavoided.

Non linear and resistive MHD leads to more complex phenomenae,many still under investigation

β = =p

B2 / 2µ0

kinetic pressure

magnetic pressure

JG00.106/41

Instabilities

1) Magneto hydrodynamic instabilities

At rational flux surfaces (q=m/n with m and n integer numbers)resonant modes can occur.

These influence particle and heat transport.

2) Turbulence:

Turbulence spectrum is very complex due to many degrees offreedom.

Electrostatic turbulence: Important for both ion and electronheat transport.

Electromagnetic turbulence: Important for electron heattransport.

Reversed or low magnetic shear has stabilising effect onturbulence.

JG00.106/42

G. H

amm

et

Sta

ble

Pen

du

lum

Un

stab

le In

vert

ed P

end

ulu

m

Den

sity

-str

atif

ied

flu

idIn

vert

ed-d

ensi

ty f

luid

LL

(rig

id r

od)

⇒ R

ayle

igh-

Tayl

or In

stab

ility

Inst

abili

ty

M

F =

Mg

g

ω =

(g/

L)1/

2

ρ =

exp

(-y/

L)ρ

= e

xp( -

y/L)

ω =

(-

g/|L

|)1/

2 =

i(-

g/|L

|)1/

2 =

iγ

Max

gro

wth

rat

e γ

= (

g/L)

1/2

stab

le ω

= (

g/L)

1/2

JG99.342/11c

JG00

.106

/41

JG00.106/43

JG10

6/42

R

B =

"lig

ht fl

uid"

g eff =

cen

trifu

gal f

orce

plas

ma

= h

eavy

flui

d

v2 R

JG99.338/

2cTop

view

of T

oroi

dal p

lasm

a:G

row

th r

ate:

Sim

ilar

inst

abili

ty m

echa

nism

inM

HD

& d

rift/m

icro

inst

abili

ties

γ =

=g e

ff L

v t2

RL

“Bad

Curv

ature

” in

stab

ility

in p

lasm

as≈

Inve

rted P

endulu

m /

Ray

leig

h–T

aylo

r in

stab

ility

G. H

amm

et

JG00.106/44

Stabilising gross MHD instabilities

Twist in B carries plasma from bad curvature region to goodcurvature region:

Similar to how twirling a honey dipper can prevent honey fromdripping.

Tokamaks are stable , on average up to a critical pressure

G. Hammett

Unstable

Gravity

JG99.338/3c

Gravity

Gravity

Purely toroidal B

Stable

Twisting B

→

JG00.106/45

Pul

se N

o: 4

0847

P

ulse

No:

408

47

Hig

h P

erf

orm

ance

by

Opera

ting D

isch

arge

Clo

se t

o M

HD

Sta

bili

ty B

oundar

y

20 10 0 10R

F

Power(MW)

Energy(MJ)

4.0

4.5

5.0

5.5

6.0

Tim

e (s

)6.

57.

07.

58.

0JG98.722/21c

RDD(1016)

bθ(n = 1)

Dα(a.u.)

βN

NB

I

5 0 10 5 02.

0

1.0 0

•

•R

eal t

ime

cont

rol o

f hea

ting

pow

er a

llow

s op

erat

ion

clos

e to

MH

D s

tabi

lity

boun

dary

for

mor

e th

an 1

sec

ond,

avo

idin

g di

srup

tion

and

achi

evin

g hi

ghes

t neu

ton

rate

(5.

4x10

16 s–1

)JG99.145/15c

NO

wal

l

2.5

2.0

(L

→ H

)6.8

7.0

6.4

6.0

5.8

5.6 5.

45.

2

1.5

1.0

0.5 0

45

76

β(0)

/<β>

β N

8

MH

D s

tabi

lity

limit

with

JE

T w

all JG

00.1

06/4

5

JG00.106/46

Str

uct

ure

of

Neocl

assi

cal Te

arin

g M

odes

SX

R T

omog

raph

y

Fla

tteni

ng in

Te

Isla

nd E

volu

tion

•M

ode

stru

ctur

e sh

ows

an n

=2 m

ode

with

cou

pled

m=2

and

m=3

pol

oida

l har

mon

ics

•N

TM

cau

ses

loca

l fla

tteni

ng in

Te

arou

nd q

=1.5

, cha

ract

eris

tic o

f an

isla

nd

•Is

land

evo

lutio

n fo

llow

s ne

ocla

ssic

al th

eory

[Sau

ter,

Laus

anne

]

1416

1820

2224

2628

Tim

e (s

)

5P

ulse

No:

439

50P

ulse

No:

439

39P

ulse

No:

405

63

4 3 2 1 0

JG99.190/19c

δBθ

(fas

t)δB

θ (s

low

)P

oloi

dal β

w2

~ δ

Bθ

1.0

0.5 0

-0.

5

-1.

02.

53.

0R

(m

)

Z (m)

3.5

5

16.2

s<t<

16.3

s

16.7

s<t<

16.8

s

q =

1.5

4 3 2 1 0 3.2

3.4

R (

m)

Te (keV)

3.6

3.8

JG00

.106

/46

JG00.106/47

Turbulence and anomaloustransport

Small amplitude microinstabilities drive anomalous transport intokamaks

Measure small fluctuations can describe

observed transport in tokamaks (1-100 x neoclassical)

JG99

.338

/4c

0 ar

n (r)

Understanding turbulent transport is very interesting from thephysics point of view.

Micro-instabilities have smallamplitude, but still are non-linear

n = n0 (r) + n (x, t)

n0 >> n

but ∇n0 ~∇n~

~

~

~ ~ ~nn

ΦT

TT

1%~~~

JG00.106/48

JG99

.321

/11c

-0.12 0 0.12 -0.06 0 0.06

Turbulence reduction fromshear in plasma rotation

Contour plots of turbulence amplitude, (simulation)

Without Sheared Flow With Sheared FlowZ. Lin, Science 281,1835(1998)

Shear in the E x B poloidal flow (due to the dominant radialelectric field) is responsible for the reduction in amplitude andradial extent of fluctuations in density and electrostatic potential.

Theory, aided by numerical simulation, is beginning to understandthe many complex mechanisms that lead to self-regulatedturbulent transport in tokamak plasmas.

eΦT

~

→→

JG00.106/49

Confinement:The different zones

In magnetic fusion small scale microinstabilities dominatetransport.

Bifurcations to states with reduced transport occur.

Regions with reduced transport (“Transport Barriers”) can appearin the edge or the core of tokamak plasmas, (or in both).

Sawteeth

10

1

Internal Transport Barrier(ITB)

Edge Localized Modes(ELMs)

Edge TransportBarrier (ETB)

(H-mode)

Normalised radius r/a

JG98

.426

/2c

Pla

sma

Pre

ssur

e

L–mode

Core

Pedestal

JG00.106/50

PEP mode,Snakes,MonsterSawteeth

JG00.106/51

The PEP Mode(Pellet Enhanced Performance)

Injection of frozen deuterium pellets into the centre of the plasmaresult in the formation of a transport barrier in the plasma core:

The transport barrier may be due to the stabilizing effect ofreversed magnetic shear on MHD modes, associated with hollowcurrent density profiles

1.0

5

4 ICRF (8MW)

Time (s)

JG99.266/5c

3

Pellet

0.5

02 3

3.2

3.4

3.8

3.6

4.0 76

Time (s)

Majorradius (m)

54

3

2

4

6

8

9

10

Te = 11 keV

Te(keV)

ICRF(8MW)

42

Pellet

Major radius (m)

Den

sity

(x10

20 m

-3 )

4

JG00.106/52

The SnakeThe snake is a long-lived (100ms) structure that appears afterpellet injection.

This snake is a region of higher pressure plasma.

Pellet induced snakes were usually associated with (1,1) modesat the q=1 surface, but (3,2) modes were also observed.

JG00.106/53

More snakes

Snakes form spontaneously in Optimized Shear Discharges.

Fluctuation in Soft X-ray emission profile.

Blue double helix is a hot snake (polarity can invert).

• These snakes are usually associated with q=2

• More than one (2,1) mode may be present in the same surface.

• These snakes appear spontaneously.

400

300

200

Tim

e (µ

s)

100

0-1.0 -0.5 0

Z (m)0.5 1.0

JG99

.175

/8c

JG00.106/54

Monster sawteeth

Plasma are modulated by sawtooth-like oscillations.

Sawteeth can be stabalized by:

– Current profile control (avoiding q = 1 surface)

– Fast particles inside q = 1 surface

Monster sawtweeth are expected in burning plasmas due toalphas

A B

JG99.266/6c12

8

6

Ele

ctro

n te

mpe

ratu

re (

keV

)

R.F

. pow

er (

MW

)

04 5 6 7

Time (s)

Te (0)

PRF

Pulse No: 13430

8 9

36

24

12

010

JG00.106/55

ScalingLaws

JG00.106/56

Scaling LawsWind tunnel techniques in

Tokamaks

• Diffusive confinement

• If τE = τE(n,B,T,a), the invariance properties of the Fokker-Plankequations lead to a scaling relation:

• Choosing appropriate dimensionless variables:

ρ*~ ρi/a, β~ nT/B2, ν*~

the confinement time can be expressed as:

τE = ρ*α F (β,ν*, q...)

α = –1 Stochastic, λ~a

α = –2 Bohm scaling, λ~(aρi)1/2

α = –3 Gyro-Bohm, λ~ρi

→ τE ~ ~a2

Dturb

a2

λ2 / τc

τE ∝ ∝m

eB

T

a2 B2

1

ΩF

T

a2 B2F

1Ω

νvth/qR

τC = correlation time

JG00.106/57

Dimensionless IdentityExperiments

Dimensionless scaling can be tested by comparing ΩτE valuesin different machines with identical values of ρ*, β, ν*, q.

DIII-D

JET

1.690.552.150.16

R(m) = a (m) =B(T) =τE(s)=

JET2.960.951.070.32Predicted (0.31 actual)

DIII-D

JG99

.338

/5c

JG00.106/58

Extrapolation to a reactor

Scaling laws, derived from experimental data from variousmachines, are used to extrapolate confinement time estimatesto other devices.

JET is nearest to the reactor range, and tritium experiments

provide mass scaling: (∝mB2, more favourable than

Bohm)

ASDEX

D3D

JET

JFT2M

PBXM

PDX

AUG

CMOD

COMPASS

JT60U

TCV

ITER

ITER

10

1

0.1

0.01

0.01 0.1

RMSE = 15.8%

ITER-RC

ΩτE,fit = ρ*-2.83 β-0.8 ν*-0.1

1

Confinement time derived from scalingτE, fit (s)

10

Con

finem

ent t

ime

from

exp

erim

ents

τ E, t

h (s

)

JG99

.342

/18c

τE ∝ ρ*-3mB

JG00.106/59

and JET can use Tritium,providing information on Mass scaling

Core confinement time exhibits near gyro-Bohm scaling withτE ∝ (m/B)ρ*–3 (∝ m B2, cheaper than Bohm)

10-110-1

10

101

102

10 101 102

B τEfit ∝ M ρ*-2.83 β-0.5 ν

*-0.1 (Ts)

B τ

E (e

xper

imen

tal)

(Ts)

D-T ELMy H-mode

ITERJET

JG99

.342

/5c

ITER(βN = 2.4)

2.2

<β N < 2

.9

1.3 <β N <

1.7

JG00.106/60

Separ

ate P

lasm

a E

nerg

y in

to P

edest

al a

nd C

ore

•P

edes

tal e

nerg

y sc

ales

str

ongl

y w

ith m

ass

(M0.

5 ) as

if e

dge

is a

t ide

al p

ress

ure

limit.

•S

ubtr

actin

g pe

dest

al e

nerg

y fr

om to

tal p

lasm

a en

ergy

res

ults

in c

ore

co

nfin

emen

t tim

eco

nsis

tent

with

gyr

o-B

ohm

sca

ling

(M–0

.2)

Con

finem

ent i

s su

m o

f cor

e +

edge

: ω

c τ E

~ <

ρ*>–3

(1 +

c <

ρ*>2 /β

N2 )

Ped

esta

lC

ore

JG99.145/10c

0

0.4

0.3

0.2

0.1

0.5 0

0.1

0.2

0.3

0.4

0.5

τ gyr

o-B

ohm

τcore = (Wth-Wped)/P (s)

00.

5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1.0

1.5

2.0

2.5

3.0

3.5

Wped (MJ)

0.54

I (M

Tpe

d/2)

0.5

H D D–T

T

H D D–T

T

RM

SE

= 1

8%

JG00

.106

/60

JG00.106/61

JG00

.106

/61

•H

-mod

e th

resh

old

in H

, D, D

-T a

ndT

dec

reas

es w

ith in

crea

sing

isot

ope

mas

s as

A-1.

Very

favo

urab

le fo

r ITE

R

•33

% re

duct

ion

in p

ower

to a

cces

sH

-mod

e in

pur

e tri

tium

(e.g

. dur

ing

star

t up)

.

•20

% re

duct

ion

in p

ower

to m

aint

ain

high

fusi

on o

pera

tion.

H-m

ode T

hre

shold

Pow

er

Vari

es

Inve

rsely

wit

h M

ass

002468

24

68

PT

h(sc

alin

g) =

0.7

6 n e

0.75

B R

2 A

–1 (

MW

)

PLOSS = PIN – (MW)

H D D–T

T

JG98.152/5c

dWdt

JG00.106/62

ITER Databases to which JETis a major contributor

1) L-mode and Ohmic Global Confinement

2) L–H threshold

3) H-mode ELM-free and ELMy Global Confinement

4) Profile, contains profiles for all types of pulses

5) Disruption

6) Divertor/Edge

7) Pedestal

JG00.106/63

Internal TransportBarrierITBs

JG00.106/64

Confinement bifurcation inoptimised shear

Two ‘similar’ discharges show the difference between a plasmawithout (#42428) and with (#42426) a strong internal transportbarrier.

20100

P (MW)NBI

ICRH

Ti0 (keV)

W (MJ)0

0

0

105

20

5.0 5.5 6.0Time (s)

6.5 7.0 7.5

JG99

.342

/c

48

Pulse No: 42428 Pulse No: 42426

Rneutrons (x1016 s-1)

JG00.106/65

0 1 2 3 4–2.5

–2.0

–1.5

–1.0

–0.5

0

0.5

1.0

1.5

2.0

2.5

R (m)

Z (

m)

2 3 4R (m)

0

1

2

3

4

n e (

1019

m–3

)

JG97

.291

/43

Density Profile

Magnetic Configuration

Dense Core with Optimised Shear(Pulse No: 39571, t = 7.8s)

• Strong density peaking inthe plasma core.

JG00.106/66

Continuous Operation withInternal Transport Barrier

• Substantial increases in density and ion temperature resultwithin the Internal Transport Barrier (ITB).

JG97

.563

/23c

1

2

3

4

0

Pulse No: 42940 (D–T) Bt = 3.85T

2.0 2.5 3.0 3.5 4.0Major radius (m)

n e (x

1019

m–3

)

From LIDARt = +0.8s

t = +0.6s

t = +0.3st = +0.1s

t = –0.2s

JG97

.563

/24c

10

20

30

40

0

Pulse No: 42940 (D–T)3.3MA/3.85TTimes refer to start of high power phase

∇Ti = 150 keV/m∇p = 106 Pa/m

3.0 3.2 3.4 3.6

ITB

Major radius (m)

Ti (

keV

)

t = +0.7s

t = +0.9s

t = +0.5s

t = +0.3s

t = +0.1s

t = 0s

JG00.106/67

JG99

.501

/65

JG00

.106

/67

Inte

rnal Tr

ansp

ort

Barr

iers

pro

duced b

y appro

pri

ate

heati

ng d

uri

ng p

lasm

a c

urr

ent

ram

p-u

p p

hase

In J

ET

(see

A.C

.C. S

ips

this

con

fere

nce)

•LH

CD

ass

ist a

t the

pla

sma

star

tto

pro

vide

a re

prod

ucib

le in

itial

curr

ent p

rofil

e.•

Cur

rent

ram

p at

0.4

MA

/s to

pro

vide

a br

oad

or h

ollo

w c

urre

nt p

rofil

e.•

Pre

-hea

t to

slow

dow

n cu

rren

tdi

ffusi

on.

•Lo

w d

ensi

ty ta

rget

.•

Mai

n he

atin

g be

fore

full

curr

ent

fact

or a

nd lo

w s

hear

in p

lasm

a co

re.

•R

ecor

d yi

eld

in J

ET

D-D

pla

smas

20P

ulse

No:

408

47D-

DM

kIIA

10 0 0024

024

0.4

0.2 4.

04.

55.

05.

56.

06.

57.

0

Power (MW) Power (MW)

Ip (MA)

Dα (a.u.)

ITB

I p

R (

m)

JG99.245/2c

H-m

ode

Pow

er fe

edba

ckco

ntro

lled

Neu

tron

s

ICR

H

NB

I

•In

JE

T, IT

Bs

are

best

pro

duce

dw

hen

q ax c

lose

to 2

at s

tart

of

mai

n he

atin

g.(a

lso

repo

rted

in J

T-60

, TF

TR

, RT

P.(C

Cha

llis)

3.2

0510152025

3.4

3.6

3.8

Ti (keV)

3.2

012 8 4

3.4

3.6

Maj

or r

adiu

s (m

)M

ajor

rad

ius

(m)

Te (keV)

Tim

es r

efer

to s

tart

of h

igh

pow

er p

hase

(at

5.4

s)

Pul

se N

o: 4

0847

0.7s

0.7s

0.5s

0.5s

0.2s

0.2s

t =

0s

t =

0s

1.2s

1.2s

1.4s

1.4s

Ion

tem

pera

ture

Ele

ctro

n te

mpe

ratu

re

Typi

cal t

arge

t q p

rofil

e(f

rom

MS

E +

EF

IT)

2.5

1.5

2.0

2.5

3.5

3.0

R (

m)

Safety factor q

JG99.245/3c

JG00.106/68

JG00

.106

/68

Opti

mis

ed S

hear

Dis

char

ges

in D

-T

•IT

Bs

in n

e, T

e an

d T

i rea

dily

obt

aine

d in

D-D

and

D-T

and

with

sim

ilar

pow

ers.

•8.

2MW

of

fusi

on p

ower

pro

duce

d, e

ven

thou

ghop

timis

atio

n in

com

plet

e.

JG97.563/24c

10203040 0

Pul

se N

o: 4

2940

(D

–T)

3.3M

A/3

.85T

Tim

es r

efer

to s

tart

of h

igh

pow

er p

hase ∇T

i = 1

50 k

eV/m

∇p

= 1

06 P

a/m

3.0

3.2

3.4

3.6

ITB

Maj

or r

adiu

s (m

)Ti (keV)

t = +

0.7s

t = +

0.9s

t = +

0.5s

t = +

0.3s

t = +

0.1s

t = 0

s

Pul

se N

o. 4

2746

3

.3M

A/3

.4T

PIC

RH

PN

BI

Pre-

heat

phas

e

Te

(R=

3.65

)

H-m

ode

phas

e

Tio

(keV

)

n eo

(101

9 m

–3)

ITB

20 10 0

Power (MW) PFusion (MW)Te (keV)

12 8 4 030 20 10 0

4 2 0

8 6 4 2 07.

57.

06.

56.

05.

55.

0T

ime

(s)

JG98.629/26c

Teo

JG00.106/69

JG00

.106

/69

ITB

Form

atio

n a

nd T

urb

ule

nce

Suppre

ssio

n

•H

igh

pow

er h

eatin

g ge

nera

tes

regi

on o

f hig

h to

roid

alve

loci

ty s

hear

whi

ch s

uppr

esse

s lo

w f

requ

ency

turb

ulen

ce th

roug

hout

pla

sma

core

⇒ g

loba

l dec

reas

ein

χi.

•Fo

rmat

ion

of I

TB l

inke

d, v

ia f

eedb

ack

betw

een

enha

nced

∇P

and

ExB

she

ar, t

o lo

calis

ed s

uppr

essi

onof

hig

h fre

quen

cy tu

rbul

ence

⇒ lo

calis

ed d

rop

in χ

e.

500

400

300

200

100 00

5Ti

me

(s)

67

Den

sity

fluc

tuat

ions

in p

lasm

a co

re

Frequency (kHz)

10P

ulse

No:

467

273.

4T/3

.4 M

A

8 6 4 2 20 10 0 4.5

5.0

5.5

6.0

Tim

e (s

)6.

57.

07.

5

Te (keV) (MW)

NB

I

ICR

H

3.5m

3.2m

Ref

lect

omet

erpo

sitio

n

10P

ulse

No:

467

27

8 6 4 2 03.

83.

63.

4

Insi

de -

Cor

eIT

BO

utsi

de -

Edg

e

3.2

Te (keV)

Rad

ius

(m)

6.3s

6.0s

5.5s

5.0s

Foot

JG99.145/12c

Den

sity

fluc

tuat

ions

in p

lasm

a

JG00.106/70

Fusion in JET

JG00.106/71

Fusion Power Development

The diagram encompasses :

• 10% T in D experiments in JET in 1991;

• a result from the D-T studies on TFTR(1993 to 1997);

• high fusion power and quasi steady-state fusion powerin the JET D-T experiments of 1997.

15

5

10

00 1.0 2.0 3.0 4.0 5.0 6.0

Time (s)

Fus

ion

pow

er (

MW

)

JET(1997)

JET(1997)

JET(1991)

TFTR(1994)

JG97

.565

/3c

JG00.106/72

WD

IA (M

J)(k

Pa)

Dα

(V)

Dα

(V)

Dα

(V)

5NBI 8MW 2.6T/2.6MA

3

1

10Edge electronpressure

DT 10:90

DT 50:50

DT 100:0

Pulse No: 41738

Pulse No: 41685

Pulse No: 41852

10

5

0

5

10

5

0

10

5

0

0

Time (s)20 22 2624

JG97

.410

/5c

Isotope ratio scan(with 8MW of Neutral Injection)

• Stored energy, density and edge pressure are higher in tritium.

• ELM frequency lower.

• 8MW insufficient to reach Type I ELMs in D–D.

JG00.106/73

JG99

.501

/71

JG00

.106

/73

Reco

rd S

tead

y-Sta

te D

-T Q

-val

ue

•(D

)T IC

RH

I p

= 3

.7M

A, B

T =

3.7

T, f

= 2

8MH

z D

:T =

9:9

1

•P

fus

= 1

.67M

W

PR

F =

6M

W

•Q

(3τ E

) =

0.2

2 =

Efu

s/E

in

•τ E

= 0

.87s

•H

97 =

0.9

•S

mal

l ELM

s

•T

io ~

Teo

2460

0.5

1.02460

0.5

1.5

1.00246

1314

1516

1817

Tim

e (s

)

Pul

se N

o. 4

3015

(MW)(MW) (MJ) (keV)

JG97.569/10c

PN

BI

(Dia

gnos

tic)

PIC

RH

WD

IA

6 M

W

Pfu

s =

1.6

MW H

97D

α+T

α

Teo

(E

CE

)T

io (C

XS

)

JG00.106/74

Record Fusion Energy in‘Steady State’ ELMy H-mode

• DT fusion energy 21.7 MJ in ITER geometry

• 4 MW Fusion power at Q = 0.2

• Duration of 4.5 s ( 10 x τE ) limited by NB duration

• Central Te ≈ Ti ≈ 8 keV; βN = 1.3

JG97

.535

/1c

22MJ

20

Pulse No: 42982 3.8MA/3.8T

010

0

10

02

020

0

4

0

12 13 1514 1611 1817

Time (s)

(MW

)(a

.u.)

(MJ)

(x10

18 s

–1)

(MW

)

(MJ)

PIN

Dα

Neutron rate PFusion

Fusion energy

WDIA 10MJ

24MW

βN=1.3

JG00.106/75

Alp

ha

Par

ticl

e H

eat

ing C

lear

ly O

bse

rved

•D

-T m

ixtu

re s

can

show

s:-

no o

r ve

ry w

eak

isot

ope

effe

ct o

n gl

obal

ene

rgy

conf

inem

ent;

-str

ong

corr

elat

ion

betw

een

diam

agne

tic e

nerg

y an

d op

timum

(40

:60)

D-T

mix

ture

.•

Hig

hest

ele

ctro

n te

mpe

ratu

re s

how

s a

clea

r cor

rela

tion

with

the

max

imum

alp

ha p

artic

lehe

atin

g po

wer

and

the

optim

um D

-T m

ixtu

re.

Con

firm

s pr

oces

s by

whi

ch ig

nitio

n w

ould

occ

ur in

a re

acto

r

0

1.5

1.0

0.59 81011

0.25

0.50

0.75

1.00

n T /

(nT +

nD

)

WD

IA (

MJ)

Wth

(M

J)

τ E,th

(s)

3.8M

A/3

.4T

/10.

5MW

JG98.629/21c

(60%

)

D–T

Pul

ses

(T c

once

ntra

tions

)

(50%

)(7

5%)

(92%

)

(0%

)

01

Pα(

MW

)2

13 12 11 10Te(0) (keV)

JG98.629/11c

JG00

.106

/75

JG00.106/76

JG00

.106

/76

16.1

MW

of

D-T

Fusi

on P

ow

er

•R

epro

duci

ble

hot i

on E

LM-f

ree

H-m

odes

inD

-D a

nd D

-T a

t hig

h pl

asm

a cu

rren

t and

com

bine

d N

B+

ICR

F h

eatin

g po

wer

.

•P

erfo

rman

ce in

crea

ses

until

term

inat

ing

MH

Din

edg

e (la

rge

saw

toot

h, g

iant

ELM

, ext

erna

lki

nk d

riven

by

edge

cur

rent

).

•G

ood

mix

ture

and

den

sity

con

trol

allo

wed

reco

rd fu

sion

pow

er, P

fus,

and

Q, a

lbei

ttr

ansi

ently

:

– P

fus =

16.

1MW

(>1

0MW

for

0.7s

); a

nd

– Q

tot =

Pfu

s/(P

loss

–Pα)

= 0

.94±

0.17

(Pfu

s/Pin

= 0

.62)

.

30 20 10 0

Pul

se N

o: 4

2976

Tra

nsp

Y93

0 4.

2MA

/3.6

T (

IAE

AM

L)

Tio

(ke

V)

PIN

(M

W)

Pfu

s (M

W)

Teo

(ke

V)

Qto

t

Qin D

α +

Tα

16 M

W

28 k

eV

14 k

eV 0.9

0.6

30 20 10 0

1.0

0.5 0 12

.012

.513

.0Ti

me

(s)

13.5

14.0

JG98.632/1c

JG00.106/77

Divertors

JG00.106/78

Divertor

• Plasma is forced to flow along diverted lines into a privateregion where the heat and particles can be extracted.

• This allows:

– to pump the helium ash– to control plasma-wall interactions– to radiate some power to reduce the thermal loading of

the target plates

• Results

– good agreement with theory– τρ*/τE ~ 7.5 (< 10 is required)– good impurity control

• However

– power bursts due to edge MHD (ELMs)– true steady-state operation (active cooling)

JG00.106/79

Divertor Physics

The hotter and more fusion relevant the plasma core is, the harderit is to deal with the plasma edge.

The last plasma closed flux surface can be defined by a materialwall, which scrapes off field lines.

Or topology can help: the divertor concept. An X-point is createdin the poloidal magnetic field, taking the plasma-wall interactionaway from the core.

A delicate balancing game

Plasma cleanliness: keeping impurities out

Detachment: choosing where to radiate

Divertor Closure, for particle control

He enrichment for He ash removal

Power handling

Edge Localized Modes

JG00.106/80

JG00

.106

/80

Diffe

rent

Pla

sma

Edges

Lim

iter

Div

erto

r

JG99.342/12c JG99.342/15c

JG99.342/13c

Pla

sma-

wal

l int

erac

tion

furt

her a

way

from

pla

sma

JG00.106/81

Divertor

Fuel impurities are a major threat to thesuccess of a reactor

There are two primary sources of impurities :

He ash

Plasma-wall interactions

These impurities must be controlled

Radiation reduces plasma T

Dilution of fusion fuel

Pumped Divertor

For particle control (extract ash, neutrals)

Atomic, Molecular and Materials Physics, Technology

JG00.106/82

Divertors in JET

Pre-94Mark 0No specific divertor coils.Large plasma volume,very “open”.

1994/95Mark I“open”,very flexible

1996/97Mark IIAmore “closed”,horizontal andvertical target

1998/99Mark IIGB“Gas -box” typevertical target

JG99.342/16c

JG95

.113

/66c

JG00.106/83

• After 2000 Pulses

• In inner louvre region:– No. of C atoms ~4% of D+ flux to inner leg– Retained D ~6–8% of total gas fuelling

<1018

1018 – 3 x 1018

3 x 1018 – 1019

1019 – 3 x 1019

>3 x 1019

Inner louvre

Flakes

Outerlouvre

JG99

.182

/1c

CFC tiles

Cryopump

JET MKIIa Divertor

Deuterium level(atoms cm-2)

Deposition in MkIIA

JG00.106/84

τp* (He)/τE~7.5can be achieved

• He enriched factor η ~ 0.5 [Guo, EPS]

ITER requires η > 0.1

10

Pulse No: 46536-Corner(a)

(b)

(c)

(d)

(e)

(f)

Pulse No: 46529-VerticalPNBI

PDiv

H97

HeII γ flux

∫nedl

nHe τ* ~2.7s

τ* ~0.35s

τ* ~5.8s

PRAD50

1.20.8

0.432108

4

0

2

02

1

016 18 20

Time (s)He puff

22 24

(MW

)(1

020 m

-2 )

(1020

)(1

0-4

mb)

(MW

)(1

0-6

s-1 )

TOT

JG99

.186

/5c

JG00.106/85

JG00

.106

/85

ED

GE

2D

phan

tom

, si

mula

tion a

nd a

ctual

reco

nst

ruct

ion B

olo

mete

r to

mogra

phy

L-m

ode D

L 3

9587 t

= 2

3–2

4s

-0

.5

-0

.5

-0

.5

-0

.52

.02

.53

.03

.52

.02

.53

.03

.52

.02

.53

.0R

(m

)R

(m

)R

(m

)

Ed

ge

2D

Sim

ula

tion

Exp

erim

en

tal

MW

m-

3

Z (m)

3 2 1 0

3.5

JG99.502/3c

JG00.106/86

JG00

.106

/86

Rad

iati

ve H

-modes

wit

h im

puri

ty s

eedin

g

•Im

purit

y se

edin

g re

sults

in s

mal

l ELM

s an

d a

25%

red

uctio

n in

con

finem

ent

•R

adia

tion

in th

e de

tach

ed d

iver

tor

plas

ma

mig

rate

s to

the

X-p

oint

2.2

2.4

2.6

2.8

3.0

-1.8

-1.6

-1.4

-1.2

-1.0

R (

m)

Z (m)

2.2

2.4

2.6

2.8

3.0

R (

m)

2.2

2.4

2.6

2.8

3.0

R (

m)

MW

m-3

0.0

1.0

2.0

3.0

4.0

5.0

JG99.190/20c

PR

ad/P

Hea

t = 4

3%65

%73

%

Pul

se N

o: 3

7991

Mar

kIIA

(N

2+D

2) P

NB

= 1

2MW

JG00.106/87

Eff

ect

of

Clo

sure

on D

ivert

or

Pre

ssure

and Im

puri

ties

•N

eutr

al p

ress

ure

at p

ump

stro

ngly

incr

ease

sfa

cilit

atin

g pu

mpi

ng o

f He.

Div

erto

r P

ress

ure

Im

purit

ies

•Z

eff i

n L-

mod

e pl

asm

a de

crea

ses

•E

ffect

less

pro

noun

ced

in H

-mod

edu

e to

ELM

pro

duce

d im

purit

ies

Gas

puf

f/pum

p do

es n

ot re

duce

Zef

f in

JE

T du

e to

stro

ng in

trins

ic fl

ows

Line

ave

rage

d de

nsity

(10

19 m

-3 )

Line

ave

rage

d de

nsity

(10

19 m

-3 )

3.5

3.0

2.5

2.0

1.5

1.0

0.5 0

Divertor neutral pressure (10-3 mbar)

2.0

2.5

3.0

3.5

4.0

Hor

iz.

Mar

k I

Ver

tical

Hor

iz.M

ark

IIAP

Ver

tical

Mar

k IIG

BM

kIIA

(H

)M

kIIA

(V

)M

kIIG

B

2.5

L-m

ode

2.0

1.5

1.0 1.

01.

52.

02.

53.

03.

5JG99.145/14c

Zeff

JG00

.106

/87

JG00.106/88

Technology andDiagnostics

JG00.106/89

Highlights of JET Technology

• Remote Handling Capability

– Change from Mark I divertor to MArk IIA divertor testedremote handling techniques

– Change from MArk IIA to Mark IIGB fully by remotehandling

• Remote Handling Capability

– Unique in the world

• Diagnostics developments

JG00.106/90

MascotServomanipulator Station

Master Slave

JG00.106/91

JG99

.501

/90

Ove

rvie

w o

f JE

T d

iagnost

ics

Com

pact

, VU

V c

amer

a

Act

ive

phas

ene

utra

l par

ticle

anal

yser

14M

eV N

eutr

onsp

ectr

omet

er

14M

eV N

eutr

on s

pect

rom

eter

Div

erto

r sp

ectr

osco

py

Neu

tron

act

ivat

ion

2.5M

eV T

ime-

of-f

light

neu

tron

spe

ctro

met

er

Rec

ipro

catin

g pr

obe

(a)

Cha

rge

exch

ange

reco

mbi

natio

nsp

ectr

osco

py

Rec

ipro

catin

gpr

obe

(b)

Hig

h en

ergy

neu

tral

par

ticle

ana

lyse

r Bol

omet

er c

amer

asH

ard

X-r

ay m

onito

rs

Neu

tron

yie

ld p

rofil

e m

onito

r an

d F

EB

Har

d X

-ray

mon

itors

Com

pact

, re-

entr

ant

soft

x-ra

y ca

mer

a

Com

pact

, in-

vess

elso

ft x-

ray

cam

era

Tim

e-re

solv

ed n

eutr

on y

ield

mon

itor

CC

D V

iew

ing

and

Rec

ordi

ngN

eutr

on a

ctiv

atio

n

Hig

h re

solu

tion

X-r

aycr

ysta

l spe

ctro

scop

y

JG99

.68/

3c

Bol

omet

erca

mer

as

End

osco

pe

2/3

1/2

8/1

7/8

8/1

6/7

5/6

7/8

4/5

3/4

Act

ive

phas

eso

ft X

-ray

cam

eras

O-m

ode

mic

row

ave

inte

rfer

omet

er

X-r

ay p

ulse

hei

ght s

pect

rom

eter

VU

V s

patia

l sca

n

VU

V s

patia

l sca

n

50kV

lith

ium

ato

m b

eam

VU

V a

nd X

UV

spe

ctro

scop

y of

div

erto

r pl

asm

a

Fas

t ion

and

alp

ha-p

artic

le d

iagn

ostic

LID

AR

Tho

mso

n sc

atte

ring

Div

erto

r LI

DA

R T

hom

son

scat

terin

g

Lase

r in

ject

ed tr

ace

elem

ents

Mul

ticha

nnel

far

infr

ared

inte

rfer

omet

er

Gra

zing

inci

denc

e X

UV

broa

dban

d sp

ectr

osco

py

Bra

gg r

otor

x-r

ay s

pect

rosc

opy;

VU

V b

road

band

spe

ctro

scop

y

Ele

ctro

n cy

clot

ron

emis

sion

het

erod

yne

Act

ive

phas

eso

ft X

-ray

cam

eras

14M

eV N

eutr

onsp

ectr

omet

er

Fas

t ion

and

alp

ha-p

artic

le d

iagn

ostic

2.5M

eV T

ime-

of-f

light

neu

tron

spe

ctro

met

erE

dge

LID

AR

Tho

mso

n sc

atte

ring

CC

D v

iew

ing

and

reco

rdin

g

Neu

tron

act

ivat

ion

Tim

e re

solv

edne

utro

n yi

eld

mon

itor

Div

erto

rsp

ectr

osco

pyH

-alp

ha a

nd v

isib

lelig

ht m

onito

rs B

rem

Har

d X

-ray

mon

itors

E-m

ode

refle

ctom

eter

Cor

rela

tion

refle

ctom

eter

Div

erto

r ga

s an

alys

isus

ing

Pen

ning

gau

ge

2.5M

eV N

eutr

on s

pect

rom

eter

JG00

.106

/91

JG00.106/92

Measures Te (R), ne (R)

JET LIDAR Thomson scattering systems

LIght Detection And Ranging(Time of flight)

Vacuum beamlineDigitizers

Polychromator

Safety shutterCAMAC and

detection electronics

Bio-shield

Scattered light

Projectionmirrors

Collection mirrors

Laserinput mirror

Laser pulseat some instant

Vacuumvessel

H R LIDAR System

Short pulse ruby laser

Input/output shieldpenetrations

JET load assembly

JG92.87/1c

JG00.106/93

LIDAR Thomson ScatteringDiagnostic

• Measures radial profiles of electron temperature and density inJET plasmas

• Uses time-of-flight principle combined with Thomson scatteringtechnique to obtain spatially resolved measurements

• In the Thomson scattering technique, light from a monochromaticlaser is scattered and doppler shifted by fast moving electrons

• The width of the scattered spectrum is a measure of the electrontemperature and the total intensity is proportional to the density

• Using a short laser pulse (300ps ≡ 10cm) and fast detectionsystem the location of the instantaneous scattered spectrumcan also be determined by time-of-flight so the temperature anddensity profiles can be measured as the laser pulse passesthrough the plasma

JG00.106/94

Electron Temperature anddensity: a) Lidar Thomson

scattering

t1t2

t3

t3

ne

Te

λ1 λ2

λ3

t2t1

Collectionoptics

Path of

laser pulse

To Spectrometer

t3t2t1

x (m) = ct/2

R (m)

Time (ns)

Plasma

Profiles Te & ne Profiles

Signal in differentspectral channelsat different times

Position (x) givenby time-of-flight

JG99

.474

/10c

Position of laserpulse at different

times

JG00.106/95

Example of Lidar measurement:Plasma with Neutral Beam Heating

8

Ele

ctro

n te

mpe

ratu

re(k

eV)

10

20

4

02 3

Major radius (m)4

Time (s)

18MW NBI

Pulse No: 33643JET 4HzLIDAR Thomson Scattering

Ele

ctro

n de

nsity

(x10

19 m

–3)

10

20

5

02 3

Major radius (m)4

JG99

.474

/8c

JG99

.474

/8c

Time (s)

JG00.106/96

Measure q-profile:Motional Stark effect

Measure polarisation of E = vbeam x B

From polarisation angle: pitch angle of B: determine q

ππ

σ Hα

Doppler shift

Stark splitting

JG99.473/1c

BNeutral Beam

80keV Do

V

EVxB

JG00.106/97

Typical example of a MotionalStark measurement:

6.0

5

b)

4

3

q

2

1.5 2.0 2.5 3.0R (m)

3.5 4.0

JG99

.484

/7b

1

Safety factorPulse No: 47620

JG00.106/98

Timing of NBI Heating Affects q(0)

2

1

0

3

2

1

15

10

5

00 2 4 6 8 10

Time (s)

B = 2.6T

JG99

.484

/8c

I Pla

sma

(MA

)Ta

rget

qo

Pad

d (M

W)

Timing scan

theating

JG00.106/99

JG99

.501

/97

JG99.474/2c

Line

of

sigh

t

Act

ive

volu

me

DN

eutr

alB

eam

C6+ ∆λ λ o

I oI

λ

Pro

vide

s lo

cal m

easu

rem

ents

of:

∆λ →

Ti

λ o →

wc

I o →

nc

In a

ctiv

e vo

lum

e

C6+

+ D

→ C

*(5+

) +

D1+

→ C

5+ +

hν

+ D

1+

2 1 0 5270

5290

Wav

elen

gth

(Å)

Radiance (1011 photons/s/sr/cm2/Å)53

1053

30

Pul

se N

o: 3

0260

t =

11.

75s

Lens

Mirr

or

Ele

ctro

n im

pact

Pass

ive

CX

Act

ive

CX

CV

I-c(1

6.9k

eV)

CIII

-b(1

50eV

)

Con

tinuu

m

CVI-a

(460

eV)

CV

I-b(2

.1ke

V)

BeI

I-a(1

04eV

)

λ

R

Oct

ant 8 N

eutr

albe

ams

Spe

ctro

met

er

Meas

ure

Ti: C

har

ge E

xchan

ge S

pect

rosc

opy

JG00

.106

/99

JG00.106/100

Electron Temperature:b) Electron Cyclotron Emission

JG99

.474

/9c

R0

BT (R)

R1

In (R)

Major radius R

Resonant layer ω1

Receiver @ ω1

nωce0 ω

Tokamak axis

ω1

ω1 (R1) = n eB(R1)/me

Te(R) = 8π3c2In(ω(R))/ω2k

JG00.106/101

ECE measurement of electroninternal transport barrier

JG99

.474

/7c

8

7

6

5

4

3

2

1

3.2 3.3 3.4 3.5 3.6 3.7 3.8Major radius (m)

Ele

ctro

n te

mpe

ratu

re (

keV

)

1.8s

1.5s

1.6s

1.25s

1.15s

0.8s

0.6s

0.4s

0.3s

0s

JG00.106/102

Electron density: reflectometry

Critical Density

nc =

Measure the phase difference between the reference beam andthe beam reflected from the critical density layer in the plasma.

Source

Detector

Reference

JG99.474/1c

Critical densitylayer

Ls

Lr

RC

ϕ (t)

Rant.

εo me ωc2

e2

JG00.106/103

JG99

.501

/101

JG10

6/10

3

ITB

For

mat

ion

and

Turb

ulen

ce S

uppr

essi

on

•H

igh

pow

er h

eatin

g ge

nera

tes

regi

on o

f hig

hto

roid

al v

eloc

ity s

hear

whi

ch s

uppr

esse

s lo

wfre

quen

cy t

urbu

lenc

e th

roug

hout

pla

sma

core

⇒ g

loba

l dec

reas

e in

χi.

•F

orm

atio

n of

IT

B l

inke

d, v

ia f

eedb

ack

betw

een

enha

nced

∇P

and

ExB

she

ar,

tolo

calis

ed s

uppr

essi

on o

f hi

gh f

requ

ency

turb

ulen

ce ⇒

loca

lised

dro

p in

χe.

500

400

300

200

100 00

5Ti

me

(s)

67

Den

sity

fluc

tuat

ions

in p

lasm

a co

re

Frequency (kHz)

10P

ulse

No:

467

273.

4T/3

.4 M

A

8 6 4 2 20 10 0 4.5

5.0

5.5

6.0

Tim

e (s

)6.

57.

07.

5

Te (keV) (MW)

NB

I

ICR

H

3.5m

3.2m

Ref

lect

omet

erpo

sitio

n

10P

ulse

No:

467

27

8 6 4 2 03.

83.

63.

4

Insi

de -

Cor

eIT

BO

utsi

de -

Edg

e

3.2

Te (keV)

Rad

ius

(m)

6.3s

6.0s

5.5s

5.0s

Foot

JG99.145/12c

JG00.106/104

JG00

.106

/104

Turb

ule

nce

suppre

ssio

n insi

de ITB

.Power - CorePower - Edge

104

103

102

101

100

104

103

102

101

100-

400

00

400 -

400

400

0-

400

400

0-

400

400

-40

00

040

0 -40

040

00

-40

040

00

-40

040

00

-40

040

0

0-

400

400

Freq

uenc

y (k

Hz)

Freq

uenc

y (k

Hz)

Freq

uenc

y (k

Hz)

Freq

uenc

y (k

Hz)

TAE

Low

freq

uenc

y

Freq

uenc

y (k

Hz)

(e) 6

.5s

ITB

(d) 5

.5s

NB

I(c

) 5.0

s N

BI

(b) 3

.5s

ICR

H(a

) 3.0

s O

hmic

JG99.474/6c