1. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 1 ECRH Feedback Control in TEXTOR and ITER J.A. Hoekzema 2, E. Farshi 1, E. Westerhof 1, W.A. Bongers 1, M.F. Graswinckel 1, J.W. Oosterbeek 2, M.vd Pol 1 Partners in the Trilateral Euregio Cluster: 1 FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein, The Netherlands 2 Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, EURATOM Association,D-52425 Jülich, Germany Introduction on NTM feedback control ECE measurements for mode detection and localization Achievable localization of ECE and ECCD in TEXTOR and ITER

2. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 2 Intro on NTM feedback control ECRH feedback control system 1.Detect mode: MHD from pick-up coils / from ECE fluctuations.. 2.Localise mode (in real space): Via equilibrium reconstruction 3.Determine where to steer launcher to achieve appropriate deposition: Via ray/beam tracing Main problem in equilibrium reconstruction. This can be avoided by working in frequency space: 1.Detect mode in frequency space (ECE) 2.Detect deposition in frequency space (ECE response on modulation ECCD at different frequency than mode frequency) 3.Steer launcher Complications 1.Detection of the deposition may be affected by mode 2.Fast transport in MHD region 3.ECCD may destabilise MHD while detecting deposition

3. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 3 Same sightline ECE mode detection Using same sight line ECE with f ECE = f ECRH ±  f –At same f : ECRH deposition profile = ECE emission profile consequently,  dep,ECRH =  ECE –ECE at f ECRH ±  f comes from opposite sides of  dep,ECRH –Thus: localizing mode by  phase jump between the two ECE frequencies automatically matches  dep,ECRH to  mode Main problem: how to measure (backward propagating) low power ECE in ECRH beam line?

4. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 4 ECE power ECE system with 100 MHz bandwidth –ECE power expected 1.22  10 -7 W for ITER (Q=10 Scen.2, 7.6 keV at q=3/2) 1.60  10 -8 W for TEXTOR (~ 1 keV at q=3/2) –Noise level for state of the art ECE system ITER ( 20 kHz sampling) 4  10 -13 W TEXTOR ( 100 kHz sampling) 8  10 -13 W –Minimum required transmission for signal to noise ratio of 100 is 0.03 % for ITER and 0.5 % for TEXTOR

5. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 5 Receiver separates two frequencies from ECE signal ITER: gyrotron frequency 170 GHz, band-pass filters will be at 168 and 172 GHz Schematic ECE radiometer

6. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 6 Issues for technical realization of same sightline ECE Ways to couple out ECE radiation from ECRH beam line: –Grating to deflect a small fraction (MTP coupler) –Dielectric Screen to (partly) reflect ECE frequency and transmit ECRH frequency Removal relatively high power ECRH frequency from the detection system –Notch filters (e.g. dielectic screen as first stage) Complications from Remote Steering Launcher

7. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 7 MTP coupler Mirror with grating in MTP deflects 1% of forward and backward power downwards and upwards, resp. mirror grating MTP and polarizer © IAP,Nizhny Novgorod

8. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 8 Dielectric Screen Place screen in QO beam line to reflect ECE and transmit ECRH TEXTOR: f ECRH = 140 GHz, f ECE = 138, 142 GHz fused quartz 18.5 mm under 10 o

9. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 9 Dielectric Screen For limited power/pulse length screen can be placed directly in the high power beam Place screen where beam size is large Example TEXTOR beam line: largest waist 95 mm Resulting heating from 1 MW ECRH beam, 2 % abs.

10. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 10 Scheme for ITER grating Universal Polariser Forward Power Measurement Dielectric screen Mainly ECE Receiver gyrotron Waveguide notch filters Waveguide Reflected power + ECE Pin Switch

11. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 11 Bandwidth of RS Launcher in ITER 170 GHz 168 GHz172 GHz Steering angle 5 o 170168172 Gauss (%)999999 offset axis (mm)-  4.7  4.7 offset waist (cm)-  5.4  5.4

12. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 12 Bandwidth of RS Launcher 170 GHz 168 GHz172 GHz Steering angle 10 o 170168172 Gauss (%)918690 offset axis (mm)-  9.4  9.4 offset waist (cm)-  5.3  5.3

13. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 13 ECE and ECCD Localization ITER Q = 10 Scenario 2: R = 6.2 m, B = 5.3 T, I = 15 MA –q=3/2 at  = 0.77 ; T q=3/2 = 7.7 keV; n q=3/2 = 1.0 × 10 20 m  3 Upper Launcher ECRH system –170 GHz, 3  8 beams at 1 MW each –1 st harmonic O-mode –average launching point: R = 6484.8 mm, Z = 4110.0 mm –Gaussian wavebeam radius: 71 mm –Beam divergence: 2 o (phase front curvature 2.1 m)

14. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 14 ECE and ECCD Localization TORBEAM beam tracing calculation (ackn. E. Poli) –Injection angles:  =  35 o ;  = 55.2 o

15. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 15 ECE and ECCD Localization Deposition/Emission profiles from TORAY-FOM  =  20 o  = 61 o  =  20 o  = 52 o

16. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 16 Localisation vs poloidal injection angle in ITER  = -20 o

17. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 17 Localisation: the TEXTOR case R = 1.75 m; a = 0.465 m; B < 2.8 T; I < 800 kA ECRH: 140 GHz, 800 kW; LFS mid plane injection Example 1: HFS resonance 2.20 T, 2 nd X-mode ECR

18. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 18 Localisation: the TEXTOR case ECRH: 140 GHz, 800 kW; LFS mid plane injection Focused beam waist (1 cm) near plasma centre Example 2: HFS resonance 2.55 T, 2 nd X-mode ECR

19. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 19 Localisation: the TEXTOR case Example 3: LFS resonance 2.86 T, 2 nd X-mode ECR

20. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 20 Controlled islands with DED in TEXTOR

21. Active Control of MHD Stability, Austin, 3-5 November 2003J.A. Hoekzema, FZ-Juelich / IPP Association EURATOM-FOM FOM-Instituut voor Plasmafysica “Rijnhuizen” 21 Conclusion and discussion Same sightline ECE proposed for NTM feedback –mode detection/localisation and launcher steering in single step Detection of backward ECE in ECRH beam line –MTP mirror grating with 1 % efficiency, acceptable for ITER and TEXTOR –consequences of remote steering to be assessed further –alternative for ITER: use of dedicated “spare launcher” –dielectric screen with 35 % efficiency, acceptable for TEXTOR –alternative for screen: Fabry Perot with two thin sheets Achievable ECRH and ECE localization –ITER upper launcher: possibly rather broad deposition (beam size vs steering range to be optimised) –TEXTOR: excellent localisation, HFS resonance optimal