1. 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) 7 th Integrated Operation Scenarios Topical Group Meeting Kyoto, Japan, 18–21 October 2011 TORE SUPRA

2. Status The JE has not progressed much since the Culham meeting DIII-D : New experimental results JET : 1 st 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 2011 as 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. 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 Increase of AUG ICRF antenna loading by local gas injection (Gas) A1 ICR-4

5. 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 RF10 Gas puff 307 Reflectometer 240 Reflectometer

6. ~0.2 kW~70 kW 285/300 ~1/R L 0 deg ~1/R L Outer gap (m) D-alpha RF307 puff 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

7. ~0.2 kW 285/300 ~1/R L 0 deg ~1/R L Outer gap (m) D-alpha RF10 puff Puffing at 10 deg enhances loading at both 0 deg and at 285/300 – only global effect 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 ~0.2 kW

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

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

10. Reflectometer embedded in LHCD antenna (no horns) Confined plasma SOL 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 ICRH antLCFS filtered unfiltered Bottereau/Pham

11. 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 TORE SUPRA

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. Issue 3: Gas rate level effect on confinement / ELMs JET: Decrease of H98 by ~15% for F~10 22 el./s AUG : Tore Supra : Limiter, no H-mode, Fmax~10 21 el./s DIII-D: Decrease of H98 by ~20% for F~10 22 el./s C-Mod: TORE SUPRA

14. Poloidally spread injection near antenna Reflecto meter Li beamReciprocating probe Status JET Yes,  20° Yes, far away Yes, far but magn. connected Tested but scarce n e profiles AUG Yes,  0° Yes, far away Yes, far away, close in 2011 Tested Tore Supra Yes,  40° NoYes, far but magn. connected Tested but no reflec. prof. DIII-D Yes,  0° Yes,  25° No Not tested C-Mod Yes,  40° Not tested NSTXYes (part of the antenna) Yes,  0° KSTARPlannedYes, far away Yes TORE SUPRA ICRH with poloidally spread gas injection : status

15. 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: TORE SUPRA

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!