ADAS/SANCO (Atomic data and impurity transport codes)

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ITER plasma rotation and Ti profiles from high-resolution crystal spectroscopy R Barnsley, L-C Ingesson, A Malaquias & M O’Mullane. ADAS/SANCO (Atomic data and impurity transport codes) Evaluation of suitable impurities and ionization stages. Simulations of line and continuum emission. - PowerPoint PPT Presentation

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  • ADAS/SANCO (Atomic data and impurity transport codes) Evaluation of suitable impurities and ionization stages. Simulations of line and continuum emission. Impurity contributions to Prad and Zeff.

    Integration into ITER Vertical coverage with 2-D curved crystal optics and 2-D detectors. Two or more graphite reflectors for the region inaccessible by direct views.

    Instrument performance- Optimization of sensitivity. Simulation of signal-to-noise ratios.

    Data reduction- Study of quasi-tomographic derivation of rotation and Ti.ITER plasma rotation and Ti profiles from high-resolution crystal spectroscopyR Barnsley, L-C Ingesson, A Malaquias & M OMullane

    R Barnsley, Moscow, Nov 2003.

  • ITER-98 impurity profiles

    R Barnsley, Moscow, Nov 2003.

  • ADAS / SANCO modelled line/continuum ratios for H- and He-like Kr: Chord-integrated ratios. Reference case: f-Kr = 10-5 . Ne, Prad ~ 700 kW.ITER profiles used for SANCO and signal modelling

    R Barnsley, Moscow, Nov 2003.

  • ADAS / SANCO results for f-Kr = 10-5 . ne: (Left) Ionization balance. (Right) Radiated power components and total. Prad ~ 700 kW (integrated over plasma volume). Zeff ~ 0.01 Kr ionization stages down to ~ Kr 26+ have x-ray lines suitable for crystal Doppler spectroscopy. Most of the radiated power is not in the H- and He-like stages.

    R Barnsley, Moscow, Nov 2003.

  • ADAS / SANCO results for f-Kr = 10-5 . ne: (Left) He-like Kr 34+, 1s2-1s2p, 0.945 . (Right) H-like Kr 35+, 1s-2p, 0.923 . Line radiation: photon/cm3.s. Continuum: photon/cm3.s.. For signal calculations, Deuterium continuum was multiplied by Zeff2 (~2.22).

    R Barnsley, Moscow, Nov 2003.

  • R Barnsley, Moscow, Nov 2003.

    Schematic of a Johann spectrometer with graphite prereflector to provide shielding and allow poloidal and toroidal components of the line of sight. The wavelength range ((, and the crystal filling factor (, are both determined by the sight-tube dimensions.

  • R Barnsley, Moscow, Nov 2003.

    Accessible spectrum and spectrometer passband, in the region of the principal lines of H- and He-like Fe and Kr, for a Johann spectrometer with graphite prereflector

  • ITER-98 x-ray spectrometer array (XCS-A) 5 lines of sight Provides good neutron shielding Access to plasma remote areas

    - Signal attenuation (10% transmission) - Reflection from graphite implies narrow bandwidth (~1%)

    R Barnsley, Moscow, Nov 2003.

  • X-ray discrete multi-chord option The new system is integrated at eport9 (16 LOS)and uport3 (5 LOS)

    Direct viewing lines without graphite reflectors.Two spectral arms are used for each viewing line:

    One for He like Ar (edge)One for He like Kr (core)

    R Barnsley, Moscow, Nov 2003.

  • Multi-chord X-ray spectrometer option ISO views of eport9

    R Barnsley, Moscow, Nov 2003.

  • - Upper and lower systems give continous coverage of the plasma core r/a
  • Two or more graphite reflector based lines of sight will complete plasma coverage

    R Barnsley, Moscow, Nov 2003.

  • Option for equatorial port- Allows continuous imaging- Minimises blanket aperture

    R Barnsley, Moscow, Nov 2003.

  • X-ray Views Referred to Mid-plane Profiles

    R Barnsley, Moscow, Nov 2003.

    Approximate coverage of the combined upper-port and mid-plane x-ray arrays, referred to the mid-plane profiles.

    The region between 0.7 < r/a < 0.9 cannot be viewed directly from either port.

    This gap is covered by two or more graphite reflectors.

  • + Allows plasma imaging+ Improves S/N ratio with smaller entrance aperture and smaller detectorfs/fm = -1/cos(2B)- No real focus for B < 45fs: Sagittal focus fm: Meridional focusB: Bragg angleSpherically Bent Crystal

    R Barnsley, Moscow, Nov 2003.

  • When combined with asymmetric crystal cut, gives considerable freedom in location of foci.Toroidally Bent CrystalA Hauer, J D Kilkenny & O L Landen. Rev Sci Instrum 56(5), 1985.

    R Barnsley, Moscow, Nov 2003.

  • 2-D bent crystal(not to scale)The source is deep and optically thin.A toroidally-bent crystal is required, to place the spatial focus in the plasma.Raw spatial resolution depends on:

    - Crystal height- Chord length in plasma Chord-weighted emission Optical aberrations and crystal bending Requires / ~ 10-3 (cf. / ~ 10-4 for -focus)

    For a crystal of height h: r(Uport) ~ h/6 ~ 1 cm r(Eport) ~ h/3 ~ 2 cm r/r ~ 100 (optically)

    R Barnsley, Moscow, Nov 2003.

  • R Barnsley, Moscow, Nov 2003.

    The count-rate N( (count/s) from a spectral line with intensity I( (photon/cm2.s), is given by

    where, for a Johann spectrometer with graphite prereflector, the sensitivity function S((cm2) is given by

    The terms are: graphite peak reflectivity Pgr(, vertical divergence ( (rad), crystal reflection integral Rc( (rad), projected crystal width hx (cm), crystal height hy (cm), and the combined detector and window efficiencies ((. The fraction ( of the crystal aperture filled at a given wavelength depends on the source and beamline geometry.

  • Factors leading to choice of Bragg angleLow Bragg angle (~30) :+ Reduced dispersion: = /tan.a) Smaller first-wall penetration for a given bandwidth.b) Smaller detector movement for tuneable spectrometer.+ Larger crystal radius for a given crystal-detector arm - helpful with long sight-line.+ Greater choice of crystals for short wavelengths.+ Detector more remote from port plug. + Reduced effect of conical ray geometry for imaging optics.- Shallower input angle to detector - parallax problems with gas-chamber detector. ~ Requires a toroidal crystal for imaging at B < 45

    R Barnsley, Moscow, Nov 2003.

  • Effect of input geometry on Johann sensitivityShield aaShield bShield cabcCrystal filling factor Johann optics allow us to trade S/N with band-pass, while maintaining peak sensitivity at the central wavelength

    R Barnsley, Moscow, Nov 2003.

  • Parameters of the upper port imaging crystal spectrometersThe upper port system consists of two spectrometers, able to observe both H- and He-like lines of Ar and Kr. Toroidally bent, asymmetrically cut, crystals give enough free parameters to:1) Place the meridional (imaging) focus in the plasma~6m2) Place the sagittal (dispersion) focus in the port plug~3m3) Keep a compact crystal-detector arm~1.3m

    Crystal toroidal radii: Sagittal ~ 4mMeridional ~ 1mCrystal aperture:~25 x 25 mm2 Spatial resolution > 25mm

    Ion speciesB rangeCrystal2d (nm) range (nm)Ar XVII / XVIII26 -28SiO2(1010)0.8510.375 - 0.400Kr XXXV / XXXVI26.5 - 28.5 Ge(440)0.2000.090 - 0.096

    Detector: Aperture ~ 25mm x 100mm2-D spatial resolution < 0.1mmCandidate detectors: Advanced solid state e.g. CCD, or advanced gas detector e.g. GEM.

    R Barnsley, Moscow, Nov 2003.

  • R Barnsley, Moscow, Nov 2003.

    The count-rate N( (count/s) from a spectral line with intensity I( (photon/cm2.s), is given by

    For a Johann spectrometer with graphite prereflector, the sensitivity function S((cm2) is:

    Crystal filling factor ( = 1. Total vertical divergence (tot.No. of viewing channels nch ,

    Vertical divergence per channel (ch (rad) is: (ch = (tot / nch

    (tot ~ 0.5 rad

    nch = 35

    Reference

    Fe in 1st order

    Reference

    Kr in 2nd order

    High sensitivity option.

    Only Kr on graphite

    (Ist order)

    Graphite planes

    (002)

    (004)

    (002)

    Graphite peak

    Reflectivity Pgr

    0.3

    0.2

    0.5

    Germanium cut

    (220)

    (440)

    (220)

    Ge reflection integral Rc

    (rad

    66

    9

    34

    Crystal aperture hx , hy

    cm2

    5 x 5

    5 x 5

    5 x 5 {10 x 10}

    Window/detector

    efficiency (

    0.5

    0.5

    0.5 {0.8}

    SD Direct views

    10-7 cm2

    9.4

    1.3 *

    4.7 {30}

    SGr Graphite views

    10-7 cm2

    2.8

    0.25

    2.4 {15}

  • Outline detector specificationTotal detector height (~800 mm) = observed plasma height (~4 m) x demagnification (~0.2)Individual detector height:~160 mm for 5 detectorsDetector width in direction: ~50 mmVertical resolution:~5 mm, for >100 resolvable lines of sightHorizontal resolution:~0.1 mmQDE / Energy range:> 0.7, 6 13 keV(Uport also 3 6 keV)Average count rate density:~106 count/cm2.sPeak count rate density:~107 count/cm2.sn- background count density:~104 count/cm2.s (flux of 106 n-/cm2.s, 10% sensitivity. 90% shielding)

    Candidate detectorsThis performance is typical of detectors in use or in development for high-flux sources such as synchrotrons. Gas-microstructure proportional counters. Solid state arrays with individual pulse processing chain for each pixel.

    R Barnsley, Moscow, Nov 2003.

  • Calculated signals for reference case: f-Kr = 10-5 . Ne Prad ~ 700 kW Zeff ~ 0.01 Vertical image binned into 35 chords. Poisson noise added for 100 ms integration time.

    R Barnsley, Moscow, Nov 2003.

  • Estimated Poisson signal-to-noise ratios based on counting statistics SNR ~ (Integral counts in line) / sqrt(line + continuum + n-background). Main noise source for data reduction is continuum, not n-background. A wide operational space is available between 10-7 < f-Kr < 10-4. Uses a modest instrument sensitivity of 1.4 . 10-7 cm2 per chord. (10x higher is possible).

    R Barnsley, Moscow, Nov 2003.

  • Fits to the simulated noisy raw data Illustrative of the raw data quality (obviously) not the best method of analysis. Due to the narrower profile, chord-integral effects are less for H-lik