recent jet experiments and science issues jim strachan pppl students seminar feb. 14, 2005 jet is...
TRANSCRIPT
Recent JET Experiments and Science IssuesJim Strachan
PPPL Students seminarFeb. 14, 2005
• JET is presently world’s 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
D. Meade
NBI Shinethrough protection
Upper Dump plate
Inner wall cladding
Inner wall guard limiters
Mushrooms
Saddle coil protection
Saddle coil protection
BeBe
Outer poloidal limiters
LH + ICRH protection
KC1 coil covers
B&C tiles
Total main wall tiles = 4404
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 haveachieved many of the scaled parametersneeded for ITER
J. Pamela
JET results extend scaling to conditions closest to ITER
J. Cordey
Confinement scales like:
I R n1/3 (a/P)1/2
J. Cordey
New regimes often tested at JET to understand size scaling
Confinement is complex: with interplay between pressure gradients, MHD, and transport irregularities
PTE DTE1 TTE DTE2
Largest machines have the performance to make it worth tritium
DT experiments study tritium technology, isotope and α particle effects
D. Meade
Time Evolution of JET DT pluses
Highest Fusion Power Highest Fusion EnergyITER prototype plasma
P. Lomas
10% of heating was attributed to alpha heating
P. Thomas
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:WELM
wall ~(0.5-1.0) WELMdiv
AELMwall ~ AELM
div
ELMwall ~ ELM
div ~ 200 - 500 s
WELM = 1MJ
Be-wall loads 9 – 39 MJm-2s-1/2
(melting ~ 16 MJm-2s-1/2)
One major effort is to mitigate ELMs and scale to ITER
G. Matthews
IAEA summary 2004
Objectives are to study:
• Material migration / lifetime
• Tritium retention / inventory control
• Damage due to transients / control
350 MJ
20 MJ
JET Wall Proposal: Option 1
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
Demonstrate routine / safe operation of fully integrated ITER compatible scenarios at 3-5MA NBI power upgrade
350 MJ
20 MJ
JET Wall Proposal: option 2.
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