RFX-mod Programme Workshop 2009 – January 2009 RFX-mod Diagnostic Status and Plans S.Martini on behalf of the RFX Team

RFX-mod Programme Workshop 2009 – January 2009 IntroductionIntroduction 2008 “new entries”2008 “new entries” 2009 plans2009 plans ConclusionsConclusions

RFX-mod Programme Workshop 2009 – January 2009 RFX Achievements 2008 FIR polarimeter operational and providing data New measurements: edge T e and n e from He lines intensity ratio, impurity injection by laser Blow-off, q-profile from H pellets ablation cloud desorption diagnostic edge Thomson scattering

RFX-mod Programme Workshop 2009 – January 2009 Scope Reconstuction of B Θ profile by measurements of faraday angle. Details channels FIR radiation at μm Measurements range between 5° and 10° Time resolution 1÷3 ms Measure Faraday angles with error < 10% Future plans Installation completed during spring 2008 Measure of the magnetic axis position B Θ profile computed by Abel inversion Equilibrium computed using polarimetric measurements as constraints First polarimeter measurement in RFX-mod F. Auriemma, M. Brombin, A. Canton, E. Zilli

RFX-mod Programme Workshop 2009 – January 2009 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

RFX-mod Programme Workshop 2009 – January 2009 Sample polarimeter measurements high current & density #25570 MODEL:  &p n e $ [1-(r/a) 15 ] measurements

RFX-mod Programme Workshop 2009 – January 2009 Polarimeter summary first faraday rotation measurements on 5 calibrated chords in high current RFX-mod discharges...to do: residual oscillations at the end of the pulse automatic calibration procedure enhancing and stabilizing FIR laser output power 1 broken beam splitting grid new beam splitting system with quartz platesbetter beams alignment installation chord #1

RFX-mod Programme Workshop 2009 – January 2009 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.

RFX-mod Programme Workshop 2009 – January 2009 Thermal Helium Beam (THB) An example of results obtained using THB with CCD cameras: time evolution of edge radial profiles of T e, n e and P e. At the end of 2008 PMTs have been installed. After calibration and tests, first plasma signals have been collected.

RFX-mod Programme Workshop 2009 – January 2009 Laser Blow-Off (LBO) Same laser used for edge Thomson scattering and LBO, with a beam splitter allowing the simultaneous activation. First injections carried out ablating a Ni target, a well- suited impurity for transport studies in RFX-mod plasma. Different target thickness and optic configurations tested to optimize the Ni ablation.

RFX-mod Programme Workshop 2009 – January 2009 Sample: LBO inside QSH Island Shot #24073 at 1.2 MA. Top: line integrated SXR brightness. Centre: T e by double filter diagnostic. Bottom: dominant mode m=1,n=-7 and secondary mode m=1,n=-11 -> Ni entered inside hot structure. LBO provide Ni source inside QSH island, allowing the study of impurity transport. Lines Ni XVII and Ni XVIII (249 & 292 Å) observed, together with SXR emissivity increase

RFX-mod Programme Workshop 2009 – January 2009 q profile from pellet ablation cloud Using new fast CMOS camera, first safety factor profile, q(r), measurements in RFX- mod by observing ablation cloud of H pellets. Cloud angle has been measured

RFX-mod Programme Workshop 2009 – January 2009 q profile from pellet ablation cloud First measurements prove the possibility to measure q(r). Spatial resolution and accuracy to improve with Li pellet injector thanks to lower pellet speed and more elongated cloud. profiles agree with toroidal equilibrium model

RFX-mod Programme Workshop 2009 – January 2009 DESOrption diagnostic To seek better density control during operation, new diagnostic, DESO, implemented A series of dummy openings before each RFX-mod shot improves piezo valves flow reproducibility. By processing time evolution of in-vessel pressure, DESO computes both total number of particles supplied by the valve system and total number of particles outgassed from wall and extracted by pumping system.

RFX-mod Programme Workshop 2009 – January 2009 DESOrption diagnostic DESO measurements, coupled to other diagnostics data (masses of injected pellets, mass spectrometer measurements of particles removed from wall during He GDC’s), allows to compute 3 parameters :  Des% Desorption Factor -> ratio between particles extracted after pulse end and total ones fuelled.  DeltaPart Number of particles left in the wall after each shot -> difference between total fuelled particles and outgassed ones (in case of He GDC extracted particles are subtracted),  TotPart -> total number of particles stored in the wall since last baking or boronization procedure, computed as sum of DeltaPart for all shots since last wall conditioning.

RFX-mod Programme Workshop 2009 – January 2009 DESOrption diagnostic Des% describes wall capability to absorb particles in each shot. Correlates to I/N values more than TotPart: a non-absorbing wall (Des%>100%) forces I/N to 2  Am, corresponding to maximum sustainable n e. Conversely, DeltaPart behavior shows that more particles are stored in the wall at each shot, i.e. an effective way to prevent wall particle accumulation has not yet been found.

RFX-mod Programme Workshop 2009 – January 2009 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

RFX-mod Programme Workshop 2009 – January 2009 Edge Thomson Scattering Example of measure Red: edge Ts Blue : closest main Ts profile #25119,n 8E19 Done: acquisition has shifted from CCD camera to fast APD Status: able to measure for n> 3 x Fiber coupling and optics rearrange should shift limit to 1 x To reach lower limits a mechanical modification needed (to overcome vignetting of external channels)

RFX-mod Programme Workshop 2009 – January plans Acquiring new diagnostics in order to : Improve fundamental data set (NPA) Supplement operation of NBI on loan from TPE-RX (FILD). Enhance analysis capability at high current (Li NB diagnostic) Completion / development 2008 activities

RFX-mod Programme Workshop 2009 – January 2009 A Neutral Particle Analyser (NPA), based on re-ionization and magnetic deflection has been borrowed from the Max Planck Institute in Greifswald 22 channels analyse the ion (H,D) distribution function in the keV energy range. T i measurement from NPA

RFX-mod Programme Workshop 2009 – January 2009 T i measurement from NPA the 11 (H) channels of NPA system will be used to measure T i and detect fast ion tails. Fast data acquisition will allow 50  s count windows. Data will be analyzed using Monte Carlo codes simulating neutrals production inside the plasma: utilize modified Nené code, originally developed to reconstruct particle source term in transport simulations.

RFX-mod Programme Workshop 2009 – January 2009 Fast Ion Losses Diagnostic (FILD) To supplement high power NBI injector on loan from TPE-RX, a fast-ion diagnostic will study losses due to instabilities dedicated to a feasibility study to identify the best solution between:  Magnetic collimator spectrometer  Faraday cup collector

RFX-mod Programme Workshop 2009 – January 2009 FILD Top and side view of collimator. Gyroradius (energy) of the particle determines how far from the aperture it strikes the scintillator (left). Pitch angle determines where it strikes along the orthogonal dimension (right).

RFX-mod Programme Workshop 2009 – January 2009 FILD FILD realized with a Faraday cup collector: Charged particles penetrate through a stack of conducting foils, separated by insulating foils. Depending on their energy, they pass a number of foils before being stopped, thus causing a current signal.

RFX-mod Programme Workshop 2009 – January 2009 Lithium neutral beam diagnostic A 35 keV Li beam with current of 1 mA will penetrate the plasma up to n e ~2·10 19 m -3. n e profile obtained from intensity of selected spectral Li lines measured by a CCD camera and an array of 16 avalanche detectors 1. n e profile with high spatial resolution and bandwidth of 100 Hz 2. n e fluctuation at 16 radial positions up to 500 kHz.

RFX-mod Programme Workshop 2009 – January 2009 Collection optics (left) and poloidal section (right) for TEXTOR Lithium beam diagnostic Lithium neutral beam diagnostic

RFX-mod Programme Workshop 2009 – January 2009 Completion / further development 2008 activities Upgrade of the Diagnostic Neutral Beam Injector CXRS affected by high background due to natural charge exchange processes, particularly in outer plasma region. Maximization of optical throughput in 2008 did not increase signal enough to disentangle active CX component from dominating passive one. =>To increase the active CX emission, an upgrade of the beam performance is called for. Best solution is to decrease beam divergence with new extraction and acceleration grids. This will increase the beam current density, and favor both MSE and CXRS measurements.

RFX-mod Programme Workshop 2009 – January 2009 Diagnostic Neutral Beam: T i measurements Increased optical etendue insufficient: CX signal still dominated by passive component. Simulations (Von Hellermann code) suggested looking at O VIII rather than C VI. Yet monitoring O VIII 6068 Å with highly luminous high resolution spectrometer yielded no active CX signal. Passive O VIII core plasma emission provided T i evaluation, although uncertainties on transport coefficients and measurement geometry do not permit to exactly define radial measuring position: at high density T i ~T e, at intermediate n e T i ~ 50% T e,, while at low n e O emission too low for Doppler broadening evaluations. MST experience suggests using UV emission lines (larger effective CX cross sections) -> Calculation of such lines added in simulations and new diagnostic layout being designed, to compensate for optical fibers losses.

RFX-mod Programme Workshop 2009 – January 2009 Diagnostic Neutral Beam: B t measurements Hα measurements provided a weak beam emission signal that will be used for a first attempt to estimate B t in the center. However the weakness of the signal confirms need to restore injector current at least to original value( 2.5 equivalent A) and that smaller beam divergence should be sought for, possibly by changing the extraction grids.

RFX-mod Programme Workshop 2009 – January 2009 Completion/further development 2008 activities Microwave reflectometer After successfull commissioning of first band, installation of the other 4 bands planned for Soft X-Ray (SXR) diagnostics New horizontal SXR camera Various mechanical parts have been built and will be completed in Most electronics purchased and tested. The diagnostic will be installed on RFX in the first part of SXR Multifilter Supplies the core Te by two-foil technique. Planned to upgrade from 4 to 6 channels with an improved chord layout. Tomography vacuum and control system The new vacuum system and control computer will be installed in the first shutdown of 2009.

RFX-mod Programme Workshop 2009 – January 2009 Completion/further development 2008 activities Edge measurements Temperature and density profile from thermal He beam A first set-up, consisting of a spectrometer coupled to a CCD camera, gave T e and n e in with a time response of 80 ms at 3 radial positions. The spectrometer will be modified to accomodate 3 slits coupled to photomultipliers for a time response up to 2 MHz, suitable for T e and n e fluctuations measurements Fast insertable pneumatic system for edge probes Following the feasibility study performed during year 2008, the system will be developed in Arcless power supply for ion saturation measurement Following the design activity performed in year 2008, the construction and test of the new power supply will be carried out.

RFX-mod Programme Workshop 2009 – January 2009 Microwave Reflectometer Ka band (26  40 GHz, n e : 0.9  2·10 19 m 3 ), installed. First measurements show strong reflection when the n e > critical value : (f pe 2 = e 2 n e /(4     m e ) > f mw 2 ) Signal post-processing to extract physical information in preparation. Other 4 bands in 2009 to get fast time evolution of a 5- point density profile

RFX-mod Programme Workshop 2009 – January 2009 Upgrade of triple Langmuir probe In addition to temperature, plasma density and potential measurements added. Measurement circuit rebuilt => range of temperature measurement doubled. System for protecting circuits from plasma arcs tested and installed. New acquisition system based on optical fibers: sampling frequency increased to 5 MHz. Effect of magnetizing winding currents (up to 50 kA) on optical transmitters reduced by positioning close to vacuum vessel.

RFX-mod Programme Workshop 2009 – January 2009 impurity pellet injector Injector characteristics Pellet speed: 50÷200 m/s Pellet size: Ø0.5÷2 mm x 1÷3 mm Magazine: 30 pellets Material: Li, C, B Aims Measurement of the pitch of the magnetic field lines Transport studies First wall conditioning

RFX-mod Programme Workshop 2009 – January 2009 Impurity pellet injector Interface to RFX-mod designed and ordered. Important preparation activities completed:  Lithium handling and pellet preparation tools have developed  Tests done to determine vacuum pumping requirements to limit driver gas injection into RFX-mod.  Sabot loading parts re-design improved launch system reliability and reduced running manpower requirements. Injector to be installed in early 2009.

RFX-mod Programme Workshop 2009 – January 2009 New horizontal SXR camera Most of the electronics (acquisition) purchased; 2 prototype amplifiers tested, defining the final version of the amplification stage. The various parts of the diagnostic have been built but the final on RFX-mod will occur in 2009

RFX-mod Programme Workshop 2009 – January 2009 Completion/further development 2008 activities Impurity pellet injector Due to delay in designing injector/machine interface, injector will be mounted in beginning of It will be used with Lithium for wall conditioning and for magnetic pitch angle measurements using the new fast CMOS camera. Impurity transport studies will be also performed.

RFX-mod Programme Workshop 2009 – January 2009 RFX-mod diagnostics present & future Physical quantity nene CO 2 interferometer 84 point/10 pulse Thomson scattering 12 point edge T. scattering Microwave reflectometer TeTe 84 point/ 10 pulse Thomson scattering Spectroscopy (line intensity ratio) SXR two-filter monitor (4 chords) 12 point edge Thomson scattering SXR two-filter tomography TiTi Multichannel spectrometer Diagnostic Neutral Beam CXRS Magnetic deflection NPA Impurities & flows Multichannel visible–UV spectrometer Flat-field survey spectrometer Vacuum CTV spectrometer Interference filter array Grazing incidence spectrometer SXR–bolometric tomography Multilayer filters SXR spectrometer laser Blow-Off Solid pellet injector Diagnostic Neutral Beam CXRS Internal BMagnetic probes FIR polarimeter Q profile from H pellets + CMOS fast camera Fast insertable probbes Solid pellet injector+ CMOS fast camera

RFX-mod Programme Workshop 2009 – January 2009 RFX-mod diagnostics present & future Physical quantity Fluctuations & Turbulence SXR tomography Electrical probe arrays CO 2 interferometer GPI Microwave reflectometer FIR polarimeter Edge plasmaTriple Langmuir probe U-probe ISIS Gundestrup probe GPI edge T e & n e from He line intensity ratio Plasma-Wall Int. / influxes Surface collector and erosion probes Interference filter array CCD cameras with interference filters H  monitors CMOS fast camera

RFX-mod Programme Workshop 2009 – January 2009 Conclusions Some interesting new diagnostics became fully operational in 2008 Others made progress and should be available before summer 2009 This makes the diagnostic data set reacher and should entice more challenging experimental proposal for the RFX-mod experimental program Developement work continues and “new entries” are expected also for next year