Presentation on theme: "R Barnsley, Moscow, Nov 2003.1 ADAS/SANCO (Atomic data and impurity transport codes) - Evaluation of suitable impurities and ionization stages. - Simulations."— Presentation transcript:
R Barnsley, Moscow, Nov 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 spectroscopy R Barnsley, L-C Ingesson, A Malaquias & M O’Mullane
R Barnsley, Moscow, Nov ITER-98 impurity profiles
R Barnsley, Moscow, Nov ADAS / SANCO modelled line/continuum ratios for H- and He-like Kr: - Chord-integrated ratios. - Reference case: f-Kr = Ne, Prad ~ 700 kW. ITER profiles used for SANCO and signal modelling
R Barnsley, Moscow, Nov ADAS / SANCO results for f-Kr = ne: - (Left) Ionization balance. (Right) Radiated power components and total. - Prad ~ 700 kW (integrated over plasma volume). - Zeff ~ 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 ADAS / SANCO results for f-Kr = ne: - (Left) He-like Kr 34+, 1s 2 -1s2p, Å. (Right) H-like Kr 35+, 1s-2p, Å. - Line radiation: photon/cm 3.s. - Continuum: photon/cm 3.s.Å. - For signal calculations, Deuterium continuum was multiplied by Zeff 2 (~2.2 2 ).
R Barnsley, Moscow, Nov
8 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 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 Multi-chord X-ray spectrometer option ISO views of eport9
R Barnsley, Moscow, Nov Upper and lower systems give continous coverage of the plasma core r/a <~ Compatible with the option of discrete lines of sight, by inserting/removing shield. - Reduced number of crystals and Be windows - Spatial resolution ~10 mm. - Plasma vertical position control with soft x-ray array. - Plasma rotation measurements can still be performed by two parallel views. Core views with continuous coverage on equatorial port 9
R Barnsley, Moscow, Nov Two or more graphite reflector based lines of sight will complete plasma coverage
R Barnsley, Moscow, Nov Option for equatorial port - Allows continuous imaging - Minimises blanket aperture
R Barnsley, Moscow, Nov X-ray Views Referred to Mid-plane Profiles
R Barnsley, Moscow, Nov Allows plasma imaging + Improves S/N ratio with smaller entrance aperture and smaller detector f s /f m = -1/cos(2 B ) - No real focus for B < 45° f s: Sagittal focus f m: Meridional focus B: Bragg angle Spherically Bent Crystal
R Barnsley, Moscow, Nov When combined with asymmetric crystal cut, gives considerable freedom in location of foci. Toroidally Bent Crystal A Hauer, J D Kilkenny & O L Landen. Rev Sci Instrum 56(5), 1985.
R Barnsley, Moscow, Nov 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 / ~ (cf. / ~ for -focus) For a crystal of height h: - r(Uport) ~ h/6 ~ 1 cm - r(Eport) ~ h/3 ~ 2 cm - r/r ~ 100 (optically)
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R Barnsley, Moscow, Nov Crystal Detector Factors leading to choice of Bragg angle Low 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 Effect of input geometry on Johann sensitivity Shield “a” “a” Shield “b” Shield “c” 1 a b c Crystal Detector Crystal 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 Parameters of the upper port imaging crystal spectrometers The 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~6m 2) Place the sagittal (dispersion) focus in the port plug~3m 3) Keep a compact crystal-detector arm~1.3m Crystal toroidal radii: Sagittal ~ 4mMeridional ~ 1m Crystal aperture:~25 x 25 mm 2 Spatial resolution > 25mm Ion species B rangeCrystal2d (nm) range (nm) Ar XVII / XVIII26° -28°SiO 2 (10 10) Kr XXXV / XXXVI26.5° °Ge(440) Detector: Aperture ~ 25mm x 100mm2-D spatial resolution < 0.1mm Candidate detectors: Advanced solid state e.g. CCD, or advanced gas detector e.g. GEM.
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R Barnsley, Moscow, Nov Outline detector specification Total detector height (~800 mm) = observed plasma height (~4 m) x demagnification (~0.2) Individual detector height:~160 mm for 5 detectors Detector width in direction: ~50 mm Vertical resolution:~5 mm, for >100 resolvable lines of sight Horizontal resolution:~0.1 mm QDE / Energy range:> 0.7, 6 – 13 keV(Uport also 3 – 6 keV) Average count rate density:~10 6 count/cm 2.s Peak count rate density:~10 7 count/cm 2.s n- background count density:~10 4 count/cm 2.s (flux of 10 6 n- /cm 2.s, 10% sensitivity. 90% shielding) Candidate detectors This 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 Calculated signals for reference case: - f-Kr = Ne Prad ~ 700 kW Zeff ~ Vertical image binned into 35 chords. - Poisson noise added for 100 ms integration time.
R Barnsley, Moscow, Nov 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 < f-Kr < Uses a modest instrument sensitivity of cm 2 per chord. (10x higher is possible).
R Barnsley, Moscow, Nov 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-like Kr than for He-like. - For r/a > 0.7, lower-ionized Kr ions or lower-Z impurities are required. - Under favourable conditions, a quasi-tomographic deconvolution is possible (L-C Ingesson et al).