Recent JET Experiments and Science Issues Jim Strachan PPPL Students seminar Feb. 14, 2005

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Recent JET Experiments and Science IssuesJim
StrachanPPPL Students seminarFeb. 14, 2005

• JET is presently worlds largest tokamak, being ½
  linear dimension of ITER and twice DIII-D.
• JET has produced the highest plasma current,
  largest fusion power, longest confinement time,
  and has Tritium and Be capability
• JET first operated in 1983, making many
  contributions
• This talk will discuss some issues on
• Size scaling
• DT results
• Divertor/wall material studies
• Some references
• J. Wesson Tokamaks Oxford Sci. Publ. (2004)
  general
• G. Federici, et al, Nuclear Fusion 41, 1967
  (2001) wall processes
• J. Jacquinot, et al, Nuclear Fusion 39, 235
  (1999) DT physics

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D. Meade
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Total main wall tiles 4404
Mushrooms
Be
Be
LH ICRH protection
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The JET plasma has a shape and relationship to
its vacuum vessel which is similar to ITER,
making the JET discharges an indication of ITER
plasmas
JET plasmas have achieved many of the scaled
parameters needed for ITER
J. Pamela
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JET results extend scaling to conditions closest
to ITER
Confinement scales like I R n1/3 (a/P)1/2
J. Cordey
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New regimes often tested at JET to understand
size scaling
Confinement is complex with interplay between
pressure gradients, MHD, and transport
irregularities
J. Cordey
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DT experiments study tritium technology, isotope
and a particle effects
PTE
DTE1
TTE
DTE2
Largest machines have the performance to make it
worth tritium
D. Meade
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Time Evolution of JET DT pluses
Highest Fusion Energy ITER prototype plasma
Highest Fusion Power
P. Lomas
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10 of heating was attributed to alpha heating
P. Thomas
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One major effort is to mitigate ELMs and scale to
ITER
? Large enough for ITER relevance if Ip 3MA
Pinp 25-38 MW
Atop 0.6 m2 Alimiters 0.3-0.6 m2

• Power density estimate
• DWELMwall (0.5-1.0) DWELMdiv
• AELMwall AELMdiv
• tELMwall tELMdiv 200 - 500 ms
• DWELM 1MJ

Be-wall loads 9 39 MJm-2s-1/2 (melting 16
MJm-2s-1/2)
G. Matthews
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IAEA summary 2004
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JET Wall Proposal Option 1

• Objectives are to study
• Material migration / lifetime
• Tritium retention / inventory control
• Damage due to transients / control

350 MJ
20 MJ
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JET Wall Proposal option 2.

• Objectives
• Demonstrate low T retention
• Test de-tritiation techniques
• Study effect of Be on W erosion
• Study melt layer loss wall divertor ? ELMs
  and disruptions
• Refine control / mitigation techniques ? Limit
  disruption / ELM damage
• Operate without C - radiation

350 MJ
20 MJ
Demonstrate routine / safe operation of fully
integrated ITER compatible scenarios at 3-5MA?
NBI power upgrade
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Discussion

• JET being largest machine, and highest
  performance, and closest to ITER tests size
  scaling
• JET DT capability tests tritium technology,
  isotope effects, alpha particle effects, and
  trace tritium transport
• Similarity to ITER shape and relation to walls
  means JET tests power handling and wall material
  issues