IOS-5.2Maintaining ICRH Coupling in expected ITER regime

Spokes person: M. GonicheM.-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 MeetingKyoto, Japan, 18–21 October 2011

TORE SUPRA

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

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

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)(Gas)

(Gas)

A1

ICR-4

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

~0.2 kW

~70 kW

285/300~1/RL

0 deg~1/RL

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

~0.2 kW

285/300~1/RL

0 deg~1/RL

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 (onlyweak prompt response to puff)

• If any difference, effect on 285/300 is slightly stronger than on 0 deg

~0.2 kW

C-Mod IOS 5.2 Status: SOL Reflectometer is Operational

en

Poloidally distributed gas injection near E antenna- Reflectometry measurements not too far from E antenna

Gas puff

Poloidally distributed valve & reflectometer not too far from Q5Polidally distributed valve in Q5 side limiter under discussion

Reflectometer& Probes

Poloidally distributedvalve

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 antLCFSfiltered

unfiltered

Bottereau/Pham

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

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

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:

TORE SUPRA

Poloidally spread injection near antenna

Reflectometer

Li beam Reciprocating probe

Status

JET Yes, 20° Yes, far away

Yes, far but magn. connected

Yes, far but magn. connected

Tested but scarce ne

profiles

AUG Yes, 0° Yes, far away

Yes, far away, close in 2011

Tested

Tore Supra Yes, 40° Yes, 40°

No Yes, far but magn. connected

Tested but no reflec. prof.

DIII-D Yes , 0° Yes, 25°

No No Not tested

C-Mod Yes, 40° Yes, 40°

Not tested

NSTX Yes (part of the antenna)

Yes, 0°

KSTAR Planned Yes, far away

Yes

TORE SUPRA

ICRH with poloidally spread gas injection : status

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

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!