The future of MSE: Towards real-time measurements and current profile control in ITER and KSTAR M. F. M. de Bock a,b , D. U. B. Aussems a , R. Barnsley b , J. Chung c , G. Hommen a , J. A. van Hooft a , R. T. Huijgen a , J. Ko c , D. Johnson d , F. M. Levinton e , M. Scheffer a , B. Stratton d , and M. Walsh b a Eindhoven University of Technology, Eindhoven, The Netherlands b ITER Organization, Saint-Paul-lez-Durance, France c National Fusion Research Institute, Daejeon, Korea d ITER-US, Princeton Plasma Physics Laboratory, Princeton, NJ, U.S.A. e Novaphotonics, Princeton, NJ, U.S.A.
Motional Stark Effect • Current or q-profile • Instabilities, improved confinement, steady state … • Current profile control real-time actuators, controller, sensor q 3 2 1 ρ T ρ 3/3/2013 PAGE 1
Motional Stark Effect • MSE (Motional Stark Effect) diagnostic • Local, spectroscopic measurement of internal B-field (parts of it) g E = v x B + E s l E ’ m v k B 3/3/2013 PAGE 2
Motional Stark Effect • MSE (Motional Stark Effect) diagnostic • Local, spectroscopic measurement of internal B-field (parts of it) g E = v x B + E s l E ’ m v k B • Line splitting ~ | E | 3/3/2013 PAGE 3
Motional Stark Effect • MSE (Motional Stark Effect) diagnostic • Local, spectroscopic measurement of internal B-field (parts of it) g E = v x B + E s l E ’ m v k B • Line splitting ~ | E | • Line intensity π/σ ~ (1- cos 2 θ)/ (1+ cos 2 θ) , with cos θ = k.E/|E | 3/3/2013 PAGE 4
Motional Stark Effect • MSE (Motional Stark Effect) diagnostic • Local, spectroscopic measurement of internal B-field (parts of it) g ~ γ E = v x B + E s l γ+π/2 ~ E ’ m v k B • Line splitting ~ | E | • Line intensity π/σ ~ (1- cos 2 θ)/ (1+ cos 2 θ) , with cos θ = k.E/|E | • Line polarization angle tan γ =E.m/E.l 3/3/2013 PAGE 5
Motional Stark Effect • MSE (Motional Stark Effect) diagnostic • Local, spectroscopic measurement of internal B-field (parts of it) g E = v x B + E s l E ’ m v k • Conventional MSE B − Filter out π or σ line A B A B A B − Measure polarization angle: g Z R 0 1 2 tan( ) A B A B A B 3 Z 4 R 5 − Convert to q- and j-profiles (EFIT, Ampère’s law …) 3/3/2013 PAGE 6
Future challenges • In the measurement… • Wall reflections • Polarization dependent mirror degradation [1] • In the analysis… • Real-time polarization angles [2] [3] • Real-time q-profiles [1] H. Yuh et al., Poster HTPD conference 2012 (not published) [2] A. Malaquias et al., EPS 2003 ECA Vol. 27A, O-3.4C [3] G. Hommen et al., Plasma Phys. Control. Fusion Vol. 55 (2013) 025007 3/3/2013 PAGE 7
Wall reflections (ITER) • Background signal … • Line integrated bulk bremsstrahlung • Reflections of divertor bremsstrahlung + incandescence A B C • unknown (coatings) partially polarized • spatial-temporally non-uniform [1] H. Yuh et al., Poster HTPD conference 2012 (not published) 3/3/2013 PAGE 8
Wall reflections (ITER) • Background signal … • Line integrated bulk bremsstrahlung • Reflections of divertor bremsstrahlung + incandescence A B C A B C • Off-wavelength channels • in-situ calibration • cross-check in beam-off phases [1] H. Yuh et al., Poster HTPD conference 2012 (not published) 3/3/2013 PAGE 9
Mirror degradation (ITER) • First mirror (FM) exposed to plasma … • Imaging diagnostic, low signal Large aperture • Deposition dominated location aperture FM • Coating affects reflection and polarization! [1] H. Yuh et al., Poster HTPD conference 2012 (not published) 3/3/2013 PAGE 10
Mirror degradation (ITER) • First mirror (FM) exposed to plasma … • Coating affects reflection and polarization • Minimize effect by keeping incident angle close to normal [1] H. Yuh et al., Poster HTPD conference 2012 (not published) [2] A. Malaquias et al., EPS 2003 ECA Vol. 27A, O-3.4C 3/3/2013 PAGE 11
Mirror degradation (ITER) • Line Splitting calibration of polarization measurement • LS not affected by reflection and polarization changes • No line overlap in ITER • But: relation to B more complicated than polarization [1] H. Yuh et al., Poster HTPD conference 2012 (not published) 3/3/2013 PAGE 12
Mirror degradation (ITER) • Line Splitting calibration of polarization measurement • Cross-Calibration through equilibrium reconstruction • Simulations promising • but, very accurate fitting required • no test on yet current devices (KSTAR opportunity?) [1] H. Yuh et al., Poster HTPD conference 2012 (not published) 3/3/2013 PAGE 13
Real-time MSE • q-profile control needs real-time MSE (e.g. ITER and KSTAR goals) • Real-time 1 st time right • correct interpretation know the spectrum • minimize perturbing effects filter “best” part of spectrum • minimize assumptions retrieve “all” data from signal itself • stable and fast analysis • Following slides: KSTAR as test case • MSE on KSTAR not real-time in 1 st phase • but design is “real - time ready” 3/3/2013 PAGE 14
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement g E = v x B + E s l E ’ m v k B [4] M. De Bock et al., Rev. Sci. Instrum. Vol.79 (2008) 10F524 3/3/2013 PAGE 15
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement g E 1,a E 2,b l v a E ’ E 3,c m v b v c B 1 B 2 B 3 [4] M. De Bock et al., Rev. Sci. Instrum. Vol.79 (2008) 10F524 3/3/2013 PAGE 16
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement g E 1,a E 2,b l v a E ’ E 3,c m v b v c B 1 B 2 B 3 [4] M. De Bock et al., Rev. Sci. Instrum. Vol.79 (2008) 10F524 3/3/2013 PAGE 17
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement [9] J. Ko et al., KSTAR conference (2013) poster 25 [4] M. De Bock et al., Rev. Sci. Instrum. Vol.79 (2008) 10F524 3/3/2013 PAGE 18
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement beam 2 beam 1 beam 3 [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 19
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement [9] J. Ko et al., KSTAR conference (2013) poster 25 [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 20
Real-time MSE: spectrum simulation • Real-time measurement 1 st time right • Good understanding MSE spectrum good interpretation MSE measurement beam 2 beam 1 beam 3 [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 21
Real-time MSE: Filter design • Optical filter width and shape • “smoothing” can reduce δγ , but too much increases it! • 2 cavity, 4A wide interference filter for KSTAR δγ [degrees] [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 22
Real-time MSE: Filter design • Optical filter central wavelength position • Fine tuning by tilting. • Can be done real-time to ensure optimal signal [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 23
Real-time MSE: Extracting all information • PEM polarization measurement • polarization intensity modulation • base frequencies ( ω 1 and ω 2 ) E 1,a E 2,b • base retardances ( R 1 and R 2 ) v a E 3,c v b tan(2 g ) = J 2 ( R 2 ) I 2 w 1 v c • J 2 ( R 1 ) I 2 w 2 B 1 B 2 B 3 PEM1 harmonics PEM2 harmonics [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 24
Real-time MSE: Extracting all information • PEM polarization measurement tan(2 g ) = J 2 ( R 2 ) I 2 w 1 • J 2 ( R 1 ) I 2 w 2 E 1,a E 2,b • ω and I ω extracted with PLL v a E 3,c v b • Retardance R ??? v c x (cm) B 1 B 2 B 3 1 set value on PEM controller y (cm) …. but profile on PEM itself! average over PEM aperture [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 25
Real-time MSE: Extracting all information • PEM polarization measurement tan(2 g ) = J 2 ( R 2 ) I 2 w 1 • J 2 ( R 1 ) I 2 w 2 E 1,a E 2,b • Averaged retardance R from signal: v a E 3,c v b I 2 w 1 = - J 2 ( R 1 ) v c B 1 I 4 w 1 J 4 ( R 1 ) B 2 B 3 − measure up to 4 th harmonic [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 26
Real-time MSE: Synergy in analysis • Simple analysis: • 1 Phase Locked Loop per channel • Requires enough signal PEM 1 PEM 2 [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 27
Real-time MSE: Synergy in analysis • Simple analysis: 1 Phase Locked Loop per channel • Multi-channel analysis: • All channels go through same PEMs • Phase shift φ equal for all channels use synergy of multi-channel analysis more signal, more accurate locking, also applies to R PEM 1 PEM 2 [5] M. De Bock et al., Rev. Sci. Instrum. Vol.83 (2012) 10D524 3/3/2013 PAGE 28
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