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Background JET / ITER

Planned physics experiments with ILA J. Ongena, acting TFH Leader ERM-KMS, Association EURATOM-Belgian State, Brussels. Background JET / ITER. ITER requirements for ICRF is to couple 20 MW on plasma with two major issues : ELMy H-mode Antenna - plasma separatrix ~ 14 cm

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Background JET / ITER

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  1. Planned physics experiments with ILA J. Ongena, acting TFH LeaderERM-KMS, Association EURATOM-Belgian State, Brussels

  2. BackgroundJET / ITER • ITER requirements for ICRF is to couple 20 MW on plasma with two major issues : • ELMy H-mode • Antenna - plasma separatrix ~ 14 cm • Faraday shield recessed ~ 1cm + Faraday shield - strap ~ 5 cm =>Antenna strap - separatrix ~ 20 cm • JET ideal to study coupling in such conditions: • ICRF system with fast data acquisition • The ELMy H modes • Can operate with ROG  14 cm • Antenna strap - separatrix ~ 19 cm

  3. LH and ICRH Systems in JET LH Launcher JET-EP Antenna ICRH Antenna A ICRH Antenna B

  4. BackgroundAntenna loading in general (in L-mode conditions) • In L-mode, R variation well documented (lA ~ assumed constant) • Main dependence is exponential decrease with ROG ( antenna- cut-off density) • Example: • ROG < 4 cm => R > 3 Ohm = “good” coupling • 4 cm < ROG < 7 cm => 1.5 Ohm < R < 3 Ohm = coupling OK • 7 cm < ROG < 10 cm => R< 1 Ohm - Bad coupling Almost no data at ROG > 10 cm but very very bad coupling expected !

  5. JET’s gas injection system GIM : Gas Inlet Module GIM10 GIM12 GIM9 GIM11

  6. GIM12 GIM10 GIM9 GIM11 Antenna position in JET • Main diagnostics : • RCP, Lithium beam, edge LIDAR, fast interferometer data • Visible spectro. DD/S3-AD34 = Oct.1 vertical view  below midplane LFS • Magnetic connection of antennas to edge diagnostics : RCP, Li-beam • D2 gas injection: • From divertor GIMs 9 + 10 as in ref. • Add  level injection from GIM6 ILA

  7. Optimization of gas puff needed • ROG fixed at 14 cm • During D2 injection from GIM 6 • Improvement on ALL the antennas • During D2 injection from GIM 10 • No obvious improvement • gas injected from divertor • Fuelling less efficient ! • Also need to check effect on density, confinement, ELMs. Rc(A1) (Ohm) Rc(B1) (Ohm) Rc(C1) (Ohm) Rc(D1) (Ohm) 1022 el/s GIM6 GIM10 Da V

  8. Effect of gas injection / ROGBetween ELMS • Coupling for ROG ~14 cm very poor << 1 Ohm • D2 injection : • from divertor: • R X by 1.5 to 3 • from the midplane: • R X 2.5 to 6 ! • R up to 2 Ohm ! Good coupling ! Increasing ROG Increasing gas GIM6 @ 8 1021el/s GIM6 @ 4 1021el/s GIM 10,9 No GIM6 No gas

  9. GIM12 GIM10 GIM9 GIM11 High power ICRH at large plasma-strap distance with gas puff Coupling studies in ITER-relevant plasma configuration (dl~0.50, du~0.38) #68752, 1.9MA /3.0T 8MW power coupled ELMs present Using gas from various positions Distance antenna box-separatrix 14cm Clear effect on Te (+1 keV) and Wdia (+1 MJ)

  10. Effect of ICRH on LH coupling 3.4T/2.4MA, 51MHz, dipole phasing no gas from GIM6 • Depends on power and phasing from ICRH antennas magnetically connected to LH grill • Worse at higher power, and at -90 and monopole phasing. Effect not homogeneous poloidally • Puffing D2 near the LH launcher to increase ne,SOL alleviates problem in most cases • Also for operation with ILA in JET: will be magnetically connected

  11. Assess sheat effects • Antennae A and B viewed by the wide angle IR camera. • Specific session in 2007 dedicated to the characterisation of heating with RF • Important temperature increase with RF on upper part of septa SA SB 70439, t=59 s. PICRFA=PICRFB=2 MW

  12. A2 antennae septum temperature on JET Temperature evolution of septum A, septum B and limiter 1, pulse 70438, with power on antenna A, B and D, and NBI power. ROG= 3 cm.

  13. Physics experiments planned with ILA Questions to this group : • Details needed of currently assumed ITER scenarios : • n/nG, H98, heating scenarios, ELM size, assumed edge conditions,…. ? • What is optimal ROG in JET to mimic ITER assumed edge density conditions ? • What is optimal size of ELMs to use in JET ? • ….

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