Measurements with the final KSTAR BES diagnostic system

Measurements with the KSTAR Beam Emission Spectroscopy diagnostic systemMt LampertWigner Research Centre for PhysicsHungarian Academy of SciencesBudapest, HungaryE-mail: lampert.mate@wigner.mta.hu3rd FUSENET PhD event - 2013. 06. 25. Mt Lampert Overview of the final Beam Emission Spectroscopy Diagnosic on KSTAR

Introduction to BES2Plasma transport is dominated by turbulence causing fluctuations in plasma parameters

Beam Emission Spectroscopy (BES) is a suitable method for measuring fluctuations:The plasma is being heated by the Neutral Beam Injection (NBI)The particles of the beam are excited and emit lightThe intensity of the light is roughly proportional to the plasma densityBy measuring the light intensity, one can get information about turbulenceFrom the movement of turbulence eddies, flow velocity can be determined

Two important design constraints:Sufficient Doppler-shift (separation from edge D)View along field lines (spatial resolution)3rd FUSENET PhD event - 2013. 06. 25. Mt Lampert Overview of the final Beam Emission Spectroscopy Diagnosic on KSTAR

Schematic view of a BES systemHeidbrink, RSI, FIDA mrsekrl.2

BES diagnostic setup3Design aspects:Direct imaging from plasma to multi-channel detectorCombined system for HBES and LiBES measurementsWavelength: H: ~662nm (Doppler shifted H), Li:~670nmAPDCAM (Avalanche Photo Diode Camera):4 x 8 channel array @ 2.000.000 frame/sec 1cm by 1cm per channel spatial resolution4cm x 8cm of the plasma is measured at one shotContinuously adjustable from r/a = 0.1 to r/a = 1CCD camera: inter-shot spatial calibration, 100Hz beam imaging, full minor radius, 640x480Lithium beam density profile measurementsNovel design features of the system:Heatable and rotateable filter forWavelength tuningFilter changer for Lithium and Deuterium beam measurementsRotateable APDCAM for horizontal(4x8) and vertical (8x4) measurement

Deuterium BeamAPDCAMPeriscope in M-portTilting mirror at two anglesCCD camera3rd FUSENET PhD event - 2013. 06. 25. Mt Lampert Overview of the final Beam Emission Spectroscopy Diagnosic on KSTAR

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The BES system

RotatablemirrorCCD armInsideM portOutsideFilterAPDCAMPlasmaPrismFrontmirror

APDCAM

Stepmotor for mirror rotationTo CCD3rd FUSENET PhD event - 2013. 06. 25. Mt Lampert Overview of the final Beam Emission Spectroscopy Diagnosic on KSTAR

4BES towerBES installed in M portMeasurement possibilities5The BES system was operated by me during the 1000 shots of the 2012 campaignThe system is capable of measuring:TurbulenceAmplitude, wavelengthPoloidal velocity3D fluctuation together with Electron Cyclotron Emission imagingSignals are analyzed through Fourier / correlation methodsDuring steady state plasmaRadial density profile measurement (when NBI is modulated)

Measured signal for shot 71773rd FUSENET PhD event - 2013. 06. 25. Mt Lampert Overview of the final Beam Emission Spectroscopy Diagnosic on KSTAR

Turbulence detection6

Fluctuation level and noise levelr/a=0.65 r/a=0.8r/a=0.85r/a=1SeparatrixCore measurement: (r/a~0.7-0.8)SNR 60Fluctuation amplitude is lowAround 1 - 1.5%Noise level is 1.5 times higher then fluctuationTurbulence is hard to detect

Edge measurement: (r/a ~ 0.9-1)SNR 45Fluctuation amplitude is higherAround 3 - 4%Noise level is around the fluctuation level at channel 3Turbulence can be detected

Background fluctuation (