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

Prog WKS 2011 RFX vs RFX-mod diagnostics RFX vs RFX-mod diagnostics (from RFX Prog- Workshop 2007) MeasurementRFXRFX-mod n e CO 2 interferometerCO 2 interferometer 20 point/ 1 pulse Thomson scattering84 point/10 pulse Thomson scattering 12 point edge Thomson scatteringMicrowave reflectometer T e Multipoint Thomson scattering84 point/ 10 pulse Thomson scattering Si(Li)–pulse height analyser (PHA)12 point edge Thomson scatteringSpectroscopy (line intensity ratio) SXR two-filter monitorSXR two-filter monitor (6 chords) SXR two-filter tomography T i Multichannel spectrometerMultichannel spectrometer E||B neutral particle analyser (NPA)Diagnostic Neutral Beam CXRS TOF NPA Impurities/flowsMultichannel visible–UV spectrometer Multichannel visible–UV spectrometerFlat-field survey spectrometerVacuum CTV spectrometerInterference filter arrayGrazing incidence spectrometerSXR–bolometric tomographyMultilayer filters SXR spectrometer Solid pellet injector Diagnostic Neutral Beam CXRS laser Blow-Off

Prog WKS 2011 RFXvs RFX-mod diagnostics RFX vs RFX-mod diagnostics MeasurementRFXRFX-mod Fluctuations &SXR monitor arraySXR tomography TurbulenceElectrical probe arraysElectrical probe arrays CO 2 interferometerCO 2 interferometerMicrowave reflectometer FIR polarimeter GPI Edge plasmaLangmuir probesTriple Langmuir probe U-probe ISIS Gundestrup probe GPI edge T e & n e from He line intensity ratio Plasma-Wall Int.Surface collector and erosion probesSurface collector and erosion probes / influxes Interference filter arrayInterference filter arrayCCD cameras with interference filters H  monitorsH  monitors CMOS fast camera Internal BMagnetic probes Magnetic probes (Fast insertable pneum.)FIR polarimeter Solid pellet injector+ CMOS fast camera

Prog WKS 2011 Achievements 2010 New NPA diagnostic: First T i measurements FIR polarimeter: Repair & modification to operate at longer, => 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 Core confinement: T e & n e profiles

Prog WKS scatt. volumes on equatorial diameter (-0.95<r/a<0.85) 28 filters+APD polychormators 4 spectral channels TS signal collected through 3 ports Fiber optic delay lines multiplex (  l=15m   t=70ns): 3 positions/spectrometer ND:YLF laser ( =1053nm): E ~ 5J Pulse length ~20ns FWHM Hz Outline of the Main Thomson Scattering 70ns MHz

Prog WKS 2011 Main Thomson Scattering

Prog WKS 2011 Main Thomson scattering New laser ( Hz, old was 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 Z eff diagnostic.

Prog WKS 2011 Two independent modules (A&B) Mod. A: CO 2 & He-Ne Lasers Mod. B: CO 2 & CO Lasers 14 chords Up to 250 kHz time resolution Measurement error ≈2·10 18 m -3 MIR Interferometer

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

Prog WKS 2011 The CO 2 laser are old (moreover discontinued from repair by the manufacturer) and will be replaced in 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. CO 2 multi-chord interferometer

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

Prog WKS 2011 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 T e profile high time resolution: kHz high space resolution: 65 lines of sight 3 poloidal sections toroidal overlap

Prog WKS 2011 New horizontal SXR camera The radial profiles of T e from Thomson Scattering (black points) and from the SXR data (red triangles) at the same time for a MH pulse. 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 T e, 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.

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

Prog WKS 2011 Comparison beween temperatures calculated by SXR multifilter Black line =>T e (0) from ratio of C/B signals, green line =>T e (0) obtained from the ratio D/A. The two T e 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 Ion temperature: NPA and CXRS/DNBI

Prog WKS 2011 First T i 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 T i from low energy fluxes gives T i /T e ≥0.5 and time behaviour which, at high n e correlates well with T e from SXR multifilter. During reconnection events, fast ions generation (E>5 kEV) also seen.

Prog WKS 2011 T i 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 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 cm In one day of operation before the shutdown hints of charge exchange signal showed up in the spectrum Comparison of two spectra with and without beam. The difference corresponds to the active signal. The new duct with two 2000 l/s criopumps

Prog WKS 2011 Edge Confinement and Turbulence

Prog WKS 2011 Spherical mirror Plane mirror Vacuum window Lens To spectrometer for T e, n e profile measurements He cloud GPI 10 cm Edge n e & T e profiles (THB) and Gas Puffing Imaging Edge radial profile of n e and T e 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

Prog WKS 2011 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 T e, n e and P e (0.94<r/a<1) with time resolution of 0.5 ms. Measurements routinely available for all RFX-mod discharges.

Prog WKS 2011 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 Edge Thomson Scattering Single pulse ruby laser 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  =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 microwave frequency modulation pattern Reflectometer system on RFX-mod 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) Reflectometer vs Edge TS 27 – 31 GHz ne ~ m -3 2 μs f Full Abel reconstruction of an unknown profile requires a wide band system But.. in many cases real profiles can be assumed linear

Prog WKS 2011 Microwave Reflectometer Radial position of the cut-off layer as a function of the global electron density n e and of the parameter n e /n G The system with one IMPATT source has been routinely operating on RFX-mod in 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 electron density n e for standard and post-litization pulses

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

Prog WKS 2011 Fast Reciprocating Manipulator (FARM) The FARM design has been completed in 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 n e, T e and flow profiles in all RFX-mod plasma conditions, the investigation of turbulence and current filaments at high I p, 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 FaRM: foreseen measurements 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 (n e and T e ) –Flow (parallel and perpendicular) –Electric fields –Vorticity –Reynolds stress … r   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

Prog WKS 2011 Impurities: Z eff Diagnostics

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

Prog WKS 2011 Z eff diagnostic : new layout 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 LOS Instertable mirror with a calibrated lamp to measure reflectivity of mirror 1 Observation mirror Telescope RFX-mod Previuos position of observation mirror affected by PWI Ip Promising preliminar measurements in 2010

Prog WKS 2011 Internal Magnetic Field

Prog WKS 2011 FIR Polarimeter summary Main actions during 2010 : Recommission CO 2 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  184  m (instead of 119  m) for chords #3, 4, 6 with impact parameters respectively -0.06, +0.06, +0.31, => factor 2.4 improved measuring resolution (Faraday rotation angle   

Prog WKS 2011 FIR polarimeter chord layout 6 vertical chords (5 active) chord name h [m] ch ch ch ch ch ch FIR radiation: =118.8  m ch2ch3ch4ch5ch6ch1

Prog WKS 2011 FIR polarimeter new measurements Polarimeter measurements with =184  m Polarimeter switched to 184  m for 3 chords (#3, 4, 6) Advantage clearly seen for chords #3 & 4, which measure small angles: at 119  m 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

Prog WKS 2011 Safety factor from pellet ablation cloud

Prog WKS 2011 Magnetic field diagnostic Magnetic field profile in a RFPRelationship between pitch of the magnetic field w (r) and safety factor reversalBt=0=>vertical ablation magnetic axis Bp=0 =>horizontal ablation cloud

Prog WKS 2011 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 fps Max resolution: from 1024x1024 pixels up to 1000 fps to 128x16 pixels at fps

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

Prog WKS 2011 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 The second 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. Area covered by the horizontal PSD Area covered by the vertical PSD

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

Prog WKS 2011 Comparison measurement-theory Using 2 PSD instead of 1 the error is corrected

Prog WKS 2011 Plasma-wall interaction monitor with CMOS camera

Prog WKS 2011 Plasma-wall interaction studies Fast CMOS camera can look at the H α emission due to the plasma-wall interaction ports keys of the tiles interaction

Prog WKS 2011 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 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 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. Conclusions

Prog WKS 2011 END

Prog WKS 2011 Microwave Reflectometer In 2010 the fast driver routinely operated for a single microwave IMPATT oscillator on the Ka band giving good measurements of edge n e and showing good agreement with THB and edge Thomson Scattering. –During 2011 two new bands will be set-up and commissioned, building new drivers around existing microwave equipment. The reflectometer will thus measure the displacement of plasma layers at 3 given densities, allowing detailed studies of the edge region. –In parallel to this the old IMPATT microwave sources, which are no longer available on the market, will be substituted with sources implementing new technology.

Prog WKS 2011 Reflectometry Principle of operation rcrc rcrc Reflectometer measures the phase delay: Cut-off position from Abel inversion: O-mode wave equation: Wave reflection (cut-off) at plasma frequency: Refraction index: group delay Higher frequency waves are reflected more inside

Prog WKS 2011 Thermal Helium Beam (THB) A He atomic beam injected into plasma and 3 of its emission lines (at 667.8, and nm ) observed. Light collected from 8 different radial positions, 0 to 35 mm with a spatial resolution of 5 mm. A spectrograph is used as polychromator. The lines can be observed by: a CCD with a time resolution of ~100 µs, 3 multianode PMTs for a resolution up to 10 µs.