Active beam-based diagnostics in KSTAR

Transcription

1 Active beam-based diagnostics in KSTAR Jinseok Ko on behalf of W-H Ko a, H H Lee a, K Ida b (Charge Exchange Spectroscopy) Y-U Nam a, S Zoletnik c, M Lampert c, D Dunai c (Beam Emission Spectroscopy) J Ko a, J Chung a, and M debock d (Motional Stark Effect) a National Fusion Research Institute, Daejeon, Korea b National Institute for Fusion Science, Nagoya, Japan c Wigner Research Centre for Physics, Budapest, Hungary d Eindhoven University of Technology, Eindhoven, The Netherlands 26th ITPA-Diagnostic Spring Meeting Mon 19 Thu , Pohang, Korea 1

2 Active Beam Diagnostics: Overview Heating D beam and diagnostic Li beam are used for CES (CXRS), BES, MSE.. NBI LiBeam (1) t-ces / MSE* (Middle window) NBI (2) BES (Bottom window) NBI, Li beam *Spectrum measurements only till 2014 *Polarimetric MSE in 2015 (3) Li Zeeman (Slanted) Li beam (2016) (3) (4) p-ces (Top/Bottom) NBI (2014) (4) Beam Specifications Deuterium (Heating)** Lithium (Diagnostics) Size 24 x 60 cm (W x H) 2 5 cm (dia.) Shape Rectangular Circular Current ~ 20 A ~ 2 ma Energy kev < 60 kev Modulation 2 ~ 5 Hz ~ 250 khz ** Values are for single ion source (1) (2) 2

3 Charge Exchange Spectroscopy: Analysis and Introduction Spectroscopic analysis on CVI impurities provides ion velocity and energy since 2011 DS-spectrometer (400 mm, F/2.8, 32 channels) lent from NIFS (Japan) for KSTAR toroidal CES was installed in r & t = 0.5 (edge) 2 (core) cm & 100 Hz NBI modulation (2 5 Hz) for background (passive CX) subtraction with linear interpolation during beam-on durations 3

4 Charge Exchange Spectroscopy: Routine & Reliable Routine and reliable measurements of Ti and Vt profiles including pedestal regions V φ [km/sec] T i [kev] #5681 (2011) H-mode L-mode V φ [km/sec] T i [kev] #7082 (2012) H-mode L-mode Vφ [km/s] T i [kev] (b) H-mode 3 L-mode 2 1 KSTAR # 9422 (a) #9422 (2013) R [m] R [m] R [m] 4

5 Charge Exchange Spectroscopy: ELM suppression Changes in the pedestal structures during ELM suppression are different V φ [km/sec] Vt(3.065) w/o RMP Vt(3.115) Vt(3.825) Suppression Vt(4.115) Vt(4.915) Vt(5.215) R [m] T i [kev] Ti(3.065) w/o RMP Ti(3.115) Ti(3.825) Suppression Ti(4.115) Ti(4.915) Ti(5.215) R [m] #7821 n=1 RMP #7821(2012) : ELM control by n=1, +90 RMP (2.0kA [3~8s]) B T =1.8T, I p =0.5MA, V φ pedestal globally reduced while the Ti pedestal locally reduced in the edge. 5

6 Charge Exchange Spectroscopy: Carbon density Carbon impurity density has been estimated with several assumptions (preliminary) To do: More comprehensive effective charge exchange cross sections Stopping cross-section data from ADAS Beam attenuation code to account for the complex geometry Assumptions: n0(0) = 1e13 /m3 Analytical form for σs from [Suzuki PPCF 1998] Full:Second:Third = 0.8:0.15:0.05 Perpendicular injection of NBI Zeff = 2 with carbon dominant Emission from beam n=2 is neglected Simple ne and Te profiles 6

7 Charge Exchange Spectroscopy: Poloidal system Feasibility test for poloidal CES will be performed in the 2014 campaign CES / MSE (Middle window) BES (Bottom window) D Heating beam Li diagnostic beam Poloidal CES system (Top and bottom) Er measurements 16 channels 7

8 Beam Emission Spectroscopy: Introduction 2D image of electron density and fluctuation, turbulence Neutral beam emits line radiation proportional to the electron density Doppler-shifted line radiation can be separated from impurity lines using proper filters & optical setting BES Specifications Channels 4x8 (will be upgraded to 4x16) Spatial Resolution 1 cm (4x8 cm 2 ) Temporal Resolution S/N Ratio Meas. Position Filter Control Camera 2 MHz (up to 100 sec) ~ 150 ( ~ 2% background) Radially & Vertically selectable (shot by shot) Heating (for fine tuning) / Rotation (for calibration) Switch (for Li or D) APD (fast) & CMOS (high res.) (simultaneous) 2D images of electron density profile can be measured by avalanche photodiode camera High-speed & high signal-to-noise ratio measurements of 2D electron density Radial & Vertical Positioning 2D density profile turbulence properties turbulence propagation 8

9 Beam Emission Spectroscopy: Optics Very flexible optics allow various modes of measurements Emissions from core to edge through viewport are redirected by mirror and prism Some part of the lights are sent to CCD camera which makes simultaneous measurement with the APDCAM. Lights are imaged at this plain Retractable calibration screen is placed here Remotely adjustable mirror can direct emissions from the core or the edge to the APDCAM APDCAM is rotatable for horizontal and vertical measurements front mirror prism Heatable and rotatable filter can adjust transmit bandwidth for fine tuning and for background calibration lens array small mirror for CMOS arm focal length adjustable lens array rotatable APDCAM filter changer retractable calibration screen remotely adjustable mirror 9

10 Beam Emission Spectroscopy: What to measure What can be measured and studied? Multichannel Photon Intensity Cross Correlation btw Channels Turbulence Size Intensity Calibration Power Spectrum btw Channels w. timedelay Turbulence Propagation Background Subtraction Filtering Power Spectrum D Li GAMs Electron Density 2D Profile Reconstruction Electron Density Fluctuation btw other diagnostics Magnetic Pitch Angle 10

11 Beam Emission Spectroscopy: 2D ne profiles 2D ne profile dynamics reveal polidal propagation of ELM precursor Edge n e profile during ELM phases relaxation precursor collapse recovery 2 cm Poloidally downward recovery relaxation precursor collapse recovery Inner channel collapse recovery relaxation precursor Poloidal propagation of ELM precursor. Inclination means poloidal propagation (downward) of radially localized density structure Outer channel Nam-KPS (2014) 11

12 Beam Emission Spectroscopy: Fluctuation and turbulence Turbulence amplitude are reduced to noise level in H-mode Dα signals during L-H transitions L H H L 12

13 Motional Stark Effect: Diagnostic principle Doppler-shifted polarized light gives local field information B B LOS // E π σ π v LOS E π σ π σ π v Polarimetric (conventional) approach: Photo-elastic modulator (PEM) polarimetry Spectral approach: Stark splitting, relative intensities of multiplets 13

14 Motional Stark Effect: Spectral approach ITER relevant KSTAR approach includes spectral analysis which is ITER-relevant Total envelop MSE multiplet from ion source 1 MSE multiplet from ion source Ion source 1 (fit) Ion source 2 (fit) Total (fit) Data Unshifted Da & Ha Two CII lines MSE multiplets Edge Core Wavelength ( nm; 8.5 nm) First-time-ever spectral approach for multi-ion source NBI in KSTAR Stark-split base: free from mirror coating, Faraday effect etc (promising for ITER) Will be kept evolving as a satellite MSE system along the PEM-based MSE. Ion source 1 Ion source 2 Average Ko-JINST (2013) 14

15 Motional Stark Effect: Polarimetric (conventional) MSE - Plan Polarimetric MSE will commission in 2015 Machine hall Diagnostic room Neutral beam Plasma Collection optics Grating survey spectrometer system calibration APD Vacuum Window Sheet polarizer Interference filter Amp lock-in 1 ADC 1 Dual PEMs (Photo-Elastic Modulator) Mirror (if necessary) wall data processing lock-in 2 ADC 2 ADC 3 ADC 4 Digitizer with embedded digital lock-ins reference signals from dual PEMs 15

16 Motional Stark Effect: Polarimetric (conventional) MSE Resolutions Radial resolution better than that in ITER with a DAQ speed suitable for KSTAR The ITER MSE requirements: r/a 5 % for reasonable q profiles for NTM feedback (q = 1.5, 2) and reversed shear control. Machine r/a (%) Number of min max channels ITER JET JT-60U T DIII-D 315T TL T, 195TU < , 16 NSTX C-Mod MAST KSTAR 2 6* 30 *R = 1.75 m ION3 ION2 MSE coverage (using ION1) r = 1 3 cm (mostly 1 2 cm) MSE NBI LiBeam Emission profile (Ion source 1 in NBI1) Practical limit (photons, beam emission) Typical H-mode KSTAR 1e-5 sec 1e-3sec 1e-2 sec 1e-1 sec 1 sec PEM 20 khz (Theoretical limit) Real-time equilibrium reconstruction (50 Hz) Current relaxation t 10 msec or less seems to accommodate the various characteristic time scales in KSTAR. 16

17 Motional Stark Effect: Polarimetric (conventional) MSE Optics Careful front-optic design for both MSE (polarization) and CES (intensity) The collection optics will be shared with CES (Charge Exchange Spectroscopy) in a cassette structure inserted into the port. A polarizer is an essential element placed after the PEM and before the fibers. Dichroic beam splitter will be used to separate the CES (~ 530 nm) and MSE (~ 650 nm) signals before the polarizer that, otherwise, would attenuate the CES signals significantly. PEM Mirror Top view MSE signals go up after beam splitter (reflected) and then go through the polarizer Side view cassette Beam splitter CES signals go straight beam splitter (transmitted) Mirror and dichroic beam splitter are dielectric-coated*: - S/P reflectance ratio: ± 0.01% - S/P phase difference: ±5 in the range of operation *MLD Tech (USA) 17

18 Li-beam Zeeman Effect: Preliminary Li-beam Zeeman effect is clear near the pedestal CII ( ) Doppler-shifted Li (2S-2P) OII, CII CIII, CII, OIII CIII Feasibility checked for KSTAR with newly installed Lithium beam - Strong change in edge current profiles with external current drive was observed (2013). Dedicated diagnostic beam. No worry about the radial electric field in the measurement. Available slanted port has been reserved for the periscope. Timeline: : Conceptual design : Procurement / Installation : Commission Interaction volume at the pedestal in the midplane 18

19 Active Beam Diagnostics: Summary Summary tces pces BES pmse smse Li-Zeeman Status Operationg 2014 Operationg 2015 Operationg 2016 For Vt, Ti, nz Vp, Ti, nz, Er ne, ne fluc, turbulence r (cm) 0.5 (edge) 2 (core) 1 (edge) 10 (core) 1 Magnetic pitch, q, J 1 (edge) 2 (core) Magnetic pitch, q, J 0.5 (edge) 2 (core) Magnetic pitch, q, J (edge) t 100 Hz 100 Hz 2 MHz 100 Hz 3 Hz 100 Hz Beam NBI NBI NBI, Li NBI NBI Li 0.5 Toroidal CES: Routine and reliable (Pedestal, transport) Poloidal CES: Er BES: Various modes of operations (Transport, turbulence, MHD) MSE: ITER testbed (MHD, AT) Li-Zeeman: Er-free q & J (Pedestal, MHD, AT) 19