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

1. Recent JET Experiments and Science IssuesJim StrachanPPPL 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

2. D. Meade

3. Saddle coil protection Inner wall cladding Upper Dump plate Outer poloidal limiters Inner wall guard limiters NBI Shinethrough protection KC1 coil covers B&C tiles Saddle coil protection Total main wall tiles = 4404 Mushrooms Be Be LH + ICRH protection

4. 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

5. JET results extend scaling to conditions closest to ITER Confinement scales like: I R n1/3 (a/P)1/2 J. Cordey

6. New regimes often tested at JET to understand size scaling Confinement is complex: with interplay between pressure gradients, MHD, and transport irregularities J. Cordey

7. DT experiments study tritium technology, isotope and α particle effects PTE DTE1 TTE DTE2 Largest machines have the performance to make it worth tritium D. Meade

8. Time Evolution of JET DT pluses Highest Fusion Energy ITER prototype plasma Highest Fusion Power P. Lomas

9. 10% of heating was attributed to alpha heating P. Thomas

11. 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

12. IAEA summary 2004

13. 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

14. 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

15. 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