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RFX-mod Diagnostic systems for 2011 campaign presented by S. Martini

RFX-mod Diagnostic systems for 2011 campaign presented by S. Martini. RFX vs RFX-mod diagnostics (from RFX Prog- Workshop 2007). Measurement RFX RFX-mod n e CO 2 interferometer CO 2 interferometer 20 point/ 1 pulse Thomson scattering 84 point/10 pulse Thomson scattering

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RFX-mod Diagnostic systems for 2011 campaign presented by S. Martini

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  1. RFX-modDiagnostic systems for 2011 campaignpresented by S. Martini Prog WKS 2011

  2. RFX vs RFX-mod diagnostics (from RFX Prog- Workshop 2007) MeasurementRFXRFX-mod ne CO2 interferometer CO2 interferometer 20 point/ 1 pulse Thomson scattering 84 point/10 pulse Thomson scattering 12 point edge Thomson scattering Microwave reflectometerMicrowave reflectometer Te Multipoint Thomson scattering 84 point/ 10 pulse Thomson scattering Si(Li)–pulse height analyser (PHA) 12 point edge Thomson scattering Spectroscopy (line intensity ratio) Spectroscopy (line intensity ratio) SXR two-filter monitor SXR two-filter monitor (6 chords) SXR two-filter tomography Ti Multichannel spectrometer Multichannel spectrometer E||B neutral particle analyser (NPA)Diagnostic Neutral Beam CXRS TOF NPA Impurities/flows Multichannel visible–UV spectrometer Multichannel visible–UV spectrometer Flat-field survey spectrometer Flat-field survey spectrometer Vacuum CTV spectrometer Vacuum CTV spectrometer Interference filter array Interference filter array Grazing incidence spectrometer Grazing incidence spectrometer SXR–bolometric tomography SXR–bolometric tomography Multilayer filters SXR spectrometer Multilayer filters SXR spectrometer Solid pellet injector Diagnostic Neutral Beam CXRS laser Blow-Off Prog WKS 2011

  3. RFXvs RFX-mod diagnostics MeasurementRFXRFX-mod Fluctuations & SXR monitor array SXR tomography Turbulence Electrical probe arrays Electrical probe arrays CO2 interferometer CO2 interferometer Microwave reflectometer Microwave reflectometer FIR polarimeterFIR polarimeter GPI Edge plasma Langmuir probes Triple Langmuir probe U-probe ISIS Gundestrup probe GPI edge Te & ne from He line intensity ratio Plasma-Wall Int. Surface collector and erosion probes Surface collector and erosion probes /influxes Interference filter array Interference filter array CCD cameras with interference filters CCD cameras with interference filters HmonitorsHmonitors CMOS fast camera InternalB Magnetic probes Magnetic probes (Fast insertable pneum.) FIR polarimeterFIR polarimeter Solid pellet injector+ CMOS fast camera Prog WKS 2011

  4. Achievements 2010 • New NPA diagnostic: First Ti measurements • FIR polarimeter: Repair & modification to operate at longer l, => improved resolution • New horizontal SXR tomography camera: Operational • Microwave reflectometer: Routine operation of the Ka band • Room temperature solid pellet injector: Extensively used for wall conditioning • CXRS/DNBI: progress in the solution of the measuring problems, => produced some preliminary data. Prog WKS 2011

  5. Core confinement: Te & ne profiles Prog WKS 2011

  6. Outline of the Main Thomson Scattering Fiber optic delay lines multiplex (Dl=15m  Dt=70ns): 3 positions/spectrometer TS signal collectedthrough 3 ports 28 filters+APD polychormators 4 spectral channels 28 Digitizers @ 500MHz • ND:YLF laser (l=1053nm): • E ~ 5J • Pulse length ~20ns FWHM • 10 pulses @ 50 Hz 84 scatt. volumes on equatorial diameter (-0.95<r/a<0.85) 70ns 70ns Prog WKS 2011

  7. Main Thomson Scattering Prog WKS 2011

  8. Main Thomson scattering New laser (100 pulses @ 100Hz, old was 10 pulses @ 40 Hz ). Old YLF laser to be upgraded (to use both lasers together). => further increase number of pulses, study of transient events. Beam profiler system with fast camera installed near the laser entrance window to facilitate alignment. Modification of the diagnostic mechanical structure for easier mounting and installation of the collecting optics. Automatic windows cleaning system further developed and used for TS main windows and internal mirrors of the Zeff diagnostic. Prog WKS 2011

  9. MIR Interferometer • Two independent modules (A&B) • Mod. A: CO2 & He-Ne Lasers • Mod. B: CO2 & CO Lasers • 14 chords • Up to 250 kHz time resolution • Measurement error ≈2·1018 m-3 Prog WKS 2011

  10. RFX MIR interferometer measurements Plasma current Module A Module B Module B chords use in vessel mirrors Prog WKS 2011

  11. CO2 multi-chord interferometer The CO2 laser are old (moreover discontinued from repair by the manufacturer) and will be replaced in 2011. Laser replacement will improve reliability (new one will have a higher stability). Further improvements 2011: installation of a motorized sliding retro-reflector for calibration purpose system for remote monitoring of laser power emission. Prog WKS 2011

  12. SXR TOMOGRAPHY • SXR Bremsstrahlung radiation detected by Si photodiodes (25m-thick Beryllium foils) • 78 lines of sight • bandwidth hundreds kHz • tomographic emissivityreconstructionsbased on the Cormack-Bessel algorithm Prog WKS 2011

  13. New manipulator for SXR tomography • New horizontal manipulator silicon photodiodes 3 Be foils with different thickness: • selection of SXR energy ranges • improvement of SXR tomographic diagnostic • double-filter technique gives Te profile high time resolution: 100-200 kHz high space resolution: • 65 lines of sight • 3 poloidal sections • toroidal overlap Prog WKS 2011

  14. New horizontal SXR camera The new camera has 65 photodiodes (instead of 21) in 3 arrays of 19, 27 & 19 diodes. Each array has its own Be foil, so that the SXR tomography can be used either to reconstruct the SXR emissivity (all the arrays with same Be foil) or the Te, profile (through the two-foil technique). The space resolution is 2 cm and time resolution is ≥10kHz (up to 50kHz). A significant effort devoted to reduce EMI by the toroidal windings. The radial profiles of Te from Thomson Scattering (black points) and from the SXR data (red triangles) at the same time for a MH pulse. Prog WKS 2011

  15. SXR multifilter • New multifilter designed and built in 2009. • 8 channels for accurate time evolution of Te(0) with 5 kHz resolution. • Different Be foils installed => up to 6 independent Te(0) measurements. Prog WKS 2011

  16. Comparison beween temperatures calculated by SXR multifilter Black line =>Te(0) from ratio of C/B signals, green line =>Te(0) obtained from the ratio D/A. The two Te are basically the same, showing the cooling of the plasma when the pellet is ablated. Time resolution 5 kHz. Thickness of Be foils also shown. pellet Prog WKS 2011

  17. Ion temperature: NPA and CXRS/DNBI Prog WKS 2011

  18. First Ti data from NPA Diagnostic 11-channel NPA on loan from IPP fully commissioned in 2010 : Measurementes show “two slopes” neutral particle fluxes energy distribution. Low energy population (E<2.5 keV) presumably associated to the bulk Maxwellian. Preliminary Ti from low energy fluxes gives Ti/Te≥0.5 and time behaviour which, at high ne correlates well with Te from SXR multifilter. During reconnection events, fast ions generation (E>5 kEV) also seen. Prog WKS 2011

  19. Ti measurement from NPA During 2011 further optimization will be performed: Improved shielding of the external magnetic field Remote control (from SIGMA) of the applied voltages. Detailed interpretation of the spectra using the Nené Monte Carlo code. Prog WKS 2011

  20. Diagnostic Neutral Beam • In 2009 it was seen the beam was stopped in the duct connecting the injector to RFX. • In 2010 pumping improved adding two cryopumps and the duct cross section increased, form 10 to 15 - 20 cm • In one day of operation before the shutdown hints of charge exchange signal showed up in the spectrum The new duct with two 2000 l/s criopumps Comparison of two spectra with and without beam. The difference corresponds to the active signal. Prog WKS 2011

  21. Edge Confinement and Turbulence Prog WKS 2011

  22. Edge ne & Te profiles (THB) and Gas Puffing Imaging • Edge radial profile of ne and Te by the line intensity ratio method • Spatial resolution of 5mm in the outer 35mm of the radius for the turbulent structure measurements by the GPI system He cloud Spherical mirror GPI Plane mirror Vacuum window Lens To spectrometer for Te, ne profile measurements 10 cm Prog WKS 2011

  23. Thermal Helium Beam (THB) • 3 emission lines of He atomic beam injected into plasma observed. Light collected from 8 different radial positions, 0 to 35 mm with a spatial resolution of 5 mm: • Now measure evolution of edge profiles of Te, ne and Pe (0.94<r/a<1) with time resolution of 0.5 ms. • Measurements routinely available for all RFX-mod discharges. Prog WKS 2011

  24. Thermal Helium Beam (THB) Using conditional average technique, it is also possible to study high frequency fluctuations, and characterise the edge structures (“blobs”) Coherent structures seen as peaks in density and pressure. Prog WKS 2011

  25. Edge Thomson Scattering • Single pulse ruby laser (7J @ 694nm, 30ns at FWHM) focused on a 3mm pin-hole in vacuum. • Sapphire lens & prism deflect beam by 30° and image the pin-hole in vacuum vessel. • A camera lens (f=83mm / F#1.2) collects light at ~150°from 16 positions over f=1mm fibers: • 12 scattering volumes for Te, ∼10mm resolution; • 4 measuring points for detecting background plasma light. • The entrance port hosts the input system & the collection window  stable alignment. • Fibers are arranged in a 4x4 pattern and fed into a 4 spectral channels spectrometer. • An Intensified CCD (ICCD) acquires the Thomson and the Background signal Prog WKS 2011

  26. 27 – 31 GHz ne ~ 1019 m-3 f 2 μs Reflectometer system on RFX-mod • Full Abel reconstruction of an unknown profile requires a wide band system • But.. in many cases real profiles can be assumed linear • When the linear profile constraint, a narrow band system gives a good estimate of the cut-off layer position • Narrow band system can be extremely fast: • reliable measurements even in presence of strong density fluctuations Narrow band system (4 GHz span in 1 μs) microwave frequency modulation pattern Reflectometer vs Edge TS Prog WKS 2011

  27. Microwave Reflectometer The system with one IMPATT source has been routinely operating on RFX-mod in 2010. This allowed to perform extensive analyses over a large discharge database, as shown below: Radial position of the cut-off layer as a function of the global electron density neand of the parameter ne/nG Radial position of the cut-off layer as a function of the electron density ne for standard and post-litization pulses Prog WKS 2011

  28. f 0.5 μs Reflectometer upgrade 3 simultaneous narrow band systems (4 GHz span in 250 ns) 56 – 60 GHz ne ~ 4.2 1019 m-3 • 3 point measurement: • better profile reconstruction • turbulence radial correlation measurements • Increase of the modulation frequency: • better time resolved measurement of ne fluctuations • direct measurement of the radial propagation • compensation of errors due to Doppler shift 42 – 46 GHz ne ~ 2.4 1019 m-3 27 – 31 GHz ne ~ 1019 m-3 microwave frequency modulation pattern Prog WKS 2011

  29. Fast Reciprocating Manipulator (FARM) The FARM design has been completed in 2010. In 2011 the manipulator and a new edge probe with multiple measurements capability will be built. The aims of the new diagnostic are the reconstruction of edge ne, Te and flow profiles in all RFX-mod plasma conditions, the investigation of turbulence and current filaments at high Ip, and the measurement of the average edge current density. This latter measurement should clarify the crucial issue of ohmic constraint satisfaction in Single Helicity equilibria. Prog WKS 2011

  30. r  FaRM: foreseen measurements The Fast Reciprocating Manipulator (FaRM) is suitable for installation of different probe heads and can host up to one hundred signals. Maximum fast insertion is 100 mm The f probe head will be equipped with arrays of both magnetic and electrostatic sensors The concepts used in the U-probe head and Gundestrup head will be exploited • Radial profile of current density (useful information for plasma modeling: boundary condition input for calculation of helical equilibrium; study of power lost in the edge region) • Current density turbulent structures • Radial profiles of different quantities • Pressure (ne and Te) • Flow (parallel and perpendicular) • Electric fields • Vorticity • Reynolds stress … Prog WKS 2011

  31. Impurities: Zeff Diagnostics Prog WKS 2011

  32. Zeff from continuum Bremsstrahlung in visible range Previously too high Zeff values measured along a vertical diameter due to strong contamination of the Bremsstrahlung radiation. Detailed inspection of the spectrum and measurements at different l, identified molecules produced close to the wall as the contaminating source (molecular pseudo-continuum) Solution:=> A new Zeff diagnostics is under development measuring along a toroidal path to maximize plasma contribution relative to contaminated edge region. Prog WKS 2011

  33. Zeff diagnostic : new layout • Promising preliminar measurements in 2010 Instertable mirror with a calibrated lamp to measure reflectivity of mirror 1 • A mirror used to get toroidal LOS affected by reduction due to C ,B deposits. • Improvements: • mirror face in counter-current direction • an instertable mirror+ calibrated source allows to measure the reflectivity variation RFX-mod Ip LOS Previuos position of observation mirror affected by PWI Observation mirror Telescope Prog WKS 2011

  34. Internal Magnetic Field Prog WKS 2011

  35. FIR Polarimeter summary • Main actions during 2010 : • Recommission CO2 laser damaged by fire in 2009; • New pre-amplifier boards for the detectors •  reduced sensitivity to stray B & improved S/N ratio; • Modifications to operate with FIR laser at l = 184 mm (instead of 119 mm) for chords #3, 4, 6 with impact parameters respectively -0.06, +0.06, +0.31 , => factor 2.4 improved measuring resolution (Faraday rotation angle l2) Prog WKS 2011

  36. FIR polarimeter chord layout 6 vertical chords (5 active) ch1 ch2 ch3 ch4 ch5 ch6 FIR radiation: l=118.8 mm Prog WKS 2011

  37. FIR polarimeter new measurements Polarimeter switched to 184 mm for 3 chords (#3, 4, 6) Advantage clearly seen for chords #3 & 4, which measure small angles: at 119 mm the relative error would be >100%. Measuring error (from zero-line before/after pulse) is now 1-2°, even in the worst condition at 2 MA Polarimeter measurements with l=184 mm Prog WKS 2011

  38. Safety factor from pellet ablation cloud Prog WKS 2011

  39. Magnetic field diagnostic Magnetic field profile in a RFP Relationship between pitch of the magnetic field w(r)and safety factor q(r) @ reversal Bt=0 => vertical ablation cloud @ magnetic axis Bp=0 => horizontal ablation cloud Prog WKS 2011

  40. Cryogenic pellet injector + Fast CMOS camera Looking at the pellet from behind, the fast CMOS camera follows the time evolution of the pellet ablation cloud. Sensor: CMOS with 17μm pixel Shutter: electronic shutter from 16.7ms to 1.5μs independent of frame rate Frame rate: up to 109500 fps Max resolution: from 1024x1024 pixels up to 1000 fps to 128x16 pixels at 109500 fps Prog WKS 2011

  41. Ablation cloud time evolution penetration of the pellet inside the plasma looked with the fast CMOS camera Prog WKS 2011

  42. Pellet trajectory diagnostics Two-Dimensional Position Sensitive Device (2D-PSD) • A PN junction between two layers of resistors highly homogeneous. • The junction is photo sensitive : electrons produced by incident photons are collected at the electrodes. • The current collected at each electrode is proportional to the distance of the light source from the electrode itself. Prog WKS 2011

  43. The second PSD Area covered by the horizontal PSD Area covered by the vertical PSD • Pellet position is calculated considering the projected position on two PSD sensors. • Because of errors, the projections of the two positions do not intersect . • The assumed position of the pellet is the midpoint of the segment perpendicular to both lines. • Only a small part of the trajectory can be reconstructed. Prog WKS 2011

  44. Pellet ablation rate Ablation rate measured by PSD Hot zone Pellet trajectory Prog WKS 2011

  45. Comparison measurement-theory Using 2 PSD instead of 1the erroris corrected Prog WKS 2011

  46. Plasma-wall interaction monitor with CMOS camera Prog WKS 2011

  47. Plasma-wall interaction studies Fast CMOS camera can look at the Hαemission due to the plasma-wall interaction keys of the tiles ports interaction Prog WKS 2011

  48. Warping Using the keys of the tiles a map of the viewing area can be reconstructed This area can be warped with a fitting code The maximum position error is ± 2° Prog WKS 2011

  49. Comparison with LCFS theoretical reconstruction of the plasma LCFS radius from magnetic measurements Good agreement with the images of the fast camera with two conditions: modes m=0 are negligible if the reversal parameter is shallow (F > 0.07) modes with n>24 are negligible Prog WKS 2011

  50. Conclusions • RFX-mod is equipped of rich and powerful set of diagnostics with high temporal and spatial resolution. • New diagnostics/upgrades are expected during 2011, which will further enhance the measuring capability and the effectiveness of the next experimental campaigns. Prog WKS 2011

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