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IOS-5.2 Maintaining ICRH Coupling in expected ITER regime Spokes person: M. Goniche

TORE SUPRA. IOS-5.2 Maintaining ICRH Coupling in expected ITER regime Spokes person: M. Goniche M.-L. Mayoral (JET), R. Pinsker (DIII-D), L. Colas (TS), V. Bobkov (AUG), S. Wukitch (C-Mod), J. Hosea (NSTX), J.G. Kwak (KSTAR), S. Moriyama (JT60-U)

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IOS-5.2 Maintaining ICRH Coupling in expected ITER regime Spokes person: M. Goniche

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  1. TORE SUPRA IOS-5.2 Maintaining ICRH Coupling in expected ITER regime Spokes person: M. Goniche M.-L. Mayoral (JET), R. Pinsker (DIII-D), L. Colas (TS), V. Bobkov (AUG), S. Wukitch (C-Mod),J. Hosea (NSTX), J.G. Kwak (KSTAR), S. Moriyama (JT60-U) 7th Integrated Operation Scenarios Topical Group Meeting Kyoto, Japan, 18–21 October 2011

  2. Status The JE has not progressed much since the Culham meeting DIII-D : New experimental results JET : 1st ICRF pulse on plasma on Oct.6 AUG: No new results, planned experiment in 2011, delayed to 2012 Tore Supra: No new results due mainly to the poor availability of the ICRH system during 2011 campaign, delayed to end of 2012 C-Mod: No new results, ? NSTX: Status of edge density effect on edge RF power deposition presented at EPS11 in Strasbourg KSTAR : ? TORE SUPRA

  3. Aims for 2011as planned in April 2011 / present status Have better understanding of local modification of electron density profile near the antenna when gas is puffed new gas injection systems (DIII-D, Tore Supra, KSTAR)  Installed on DIIID and Tore Supra, KSTAR ? combined with new or upgraded reflectometer (DIII-D, C-Mod, Tore Supra)  Installed and tested (C-Mod) , installed and tested, data to be analyzed (DII-D) Exploring the role of near fields for enhancing the ionization rate and therefore the electron density. new experiments on AUG  Delayed to 2012 Investigate control in real-time  reach wanted level of coupling while minimising gas injection envisaged in JET  Still foreseen as back-up experiment Investigate the upper limit of edge density NSTX  Mine data to substantiate location of edge deposition in SOL – develop new edge diagnostics for NSTX-U TORE SUPRA

  4. Increase of AUG ICRF antenna loading by local gas injection (Gas) (Gas) A1 (Gas) ICR-4 • Local and polidally distributed gas injection improves antenna loading significantly (~×2) [Ph. Jacquet, V. Bobkov et al., to be submit.to NF] • No density measurements close to the antenna (or gas valve)  ICR moved to Ant.3 in 2011 with Li-beam close to it

  5. RF10 Gas puff 307 Reflectometer 240 Reflectometer Experiments on gas puffing to enhance Fast Wave antenna loading in DIII-D (August 2011) • Compare loading at low (0.2kW) and medium power (70kW) • 0deg and 280/300 antenna • 307 and 10 deg Gas Puff • Data available from one at 307 deg (ORNL), and 240 deg (UCLA) reflectometer (not yet analyzed) DIII-D Top view

  6. August 2011: puffing at 307 deg enhances loading at 285/300, at 0.2 kW or 70 kW, with almost no effect on 0 deg loading 285/300 ~1/RL 0 deg ~1/RL RF307 puff Outer gap (m) D-alpha ~0.2 kW ~70 kW

  7. Puffing at 10 deg enhances loading at both 0 deg and at 285/300 – only global effect 285/300 ~1/RL ~0.2 kW • Effect on 0 deg and on 285/300 loading are similar, and are tracked by D-alpha signal (only • weak prompt response to puff) • If any difference, effect on 285/300 is slightly stronger than on 0 deg 0 deg ~1/RL RF10 puff Outer gap (m) D-alpha ~0.2 kW

  8. C-Mod IOS 5.2 Status: SOL Reflectometer is Operational Gas puff Poloidally distributed gas injection near E antenna - Reflectometry measurements not too far from E antenna

  9. Poloidally distributed valve Reflectometer & Probes Poloidally distributed valve & reflectometer not too far from Q5 Polidally distributed valve in Q5 side limiter under discussion

  10. Reflectometer embedded in LHCD antenna (no horns) LCFS ICRH ant SOL filtered unfiltered Confined plasma Bottereau/Pham • Rather high S/B => detection of the plasma/vacuum interface difficult • Data processing improvement on-going • S/B improved by a factor 10 for the 2012 campaign

  11. TORE SUPRA Issue 1: Local vs Global effect in SOL JET: Not very clear (slight local effect with GIM6 puff?) AUG : Local effect for A1 (single injection point) & ICR-A (poloidally spread) (×2) Tore Supra : no local effect at rather low gas rate test higher gas rate and LHCD-assisted gas ionization DIII-D: Local effect with RF307 puff (×2) ~Global effect with 10deg puff  test poloidally spread gas puff RFCOMB C-Mod:  to be tested

  12. Issue 2: ICRF Power level effect JET: not adressed AUG : to be tested in next campaign Tore Supra : not adressed DIII-D: same Local effect with RF307 at 0.2kW & 70k  to be confirmed at ~1MW in next cmpaign C-Mod:  to be tested

  13. TORE SUPRA Issue 3: Gas rate level effect on confinement / ELMs JET: Decrease of H98 by ~15% for F~1022el./s AUG : Tore Supra : Limiter, no H-mode, Fmax~1021el./s DIII-D: Decrease of H98 by ~20% for F~1022el./s C-Mod:

  14. TORE SUPRA ICRH with poloidally spread gas injection : status

  15. TORE SUPRA Enhancement / modifications of ICRH systems for 2012-2013 JET: Metallic wall (from Oct.2011) AUG in 2012, two antennas with B-coated side limiters to make operation easier. After 2012, two new 3-strap antennas for better compatibility with W wall Tore Supra : Restart in Sept.2012 , back to 3 identical Faraday shields DIII-D: C-Mod: NSTX: Improve voltage standoff on test stand for additional power capability on NSTX Upgrade at higher B field KSTAR:

  16. Conclusions • Installation/test of new gas injection systems and density measurments (reflectometers) is almost completed • New findings on DIII-D (no IC power effect, local/global effect) need to be confirmed & more documented (use of RFCOMB on DIII-D, new experiments on AUG & other machines) • Question on how close the gas injection system has to be should be answered (comparing results from AUG, DIII-D, C-Mod, JET) • Modelling effort (expansion of neutral gas and ionization in SOL from nozzle or poloidally spread injection) needed • We expect more results in 2012!

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