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 OMullane

• 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.

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ITER-98 impurity profiles
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• 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

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• 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.

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

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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)

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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)

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Multi-chord X-ray spectrometer option
ISO views of eport9
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Core views with continuous coverage on equatorial
port 9
- Upper and lower systems give continous coverage
of the plasma core r/a lt 0.7 - 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.
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Two or more graphite reflector based lines of
sight will complete plasma coverage
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Option for equatorial port - Allows continuous
imaging - Minimises blanket aperture
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X-ray Views Referred to Mid-plane Profiles
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Spherically Bent Crystal
Allows plasma imaging Improves S/N ratio
with smaller entrance aperture and smaller
detector fs/fm -1/cos(2?B) - No real focus
for ?B lt 45 fs Sagittal focus fm Meridional
focus ?B Bragg angle
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Toroidally Bent Crystal
A Hauer, J D Kilkenny O L Landen. Rev Sci
Instrum 56(5), 1985.
When combined with asymmetric crystal cut, gives
considerable freedom in location of foci.
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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)

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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 lt 45
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Effect of input geometry on Johann sensitivity
Johann optics allow us to trade S/N with
band-pass, while maintaining peak sensitivity at
the central wavelength
Shield a
a
Crystal filling factor ?
a
b
Shield b
c
Shield c
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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 4m Meridional
1m Crystal aperture 25 x 25 mm2 Spatial
resolution gt 25mm Ion species ?B
range Crystal 2d (nm) ? range (nm) Ar XVII /
XVIII 26 -28 SiO2(10?10) 0.851 0.375 -
0.400 Kr XXXV / XXXVI 26.5 - 28.5
Ge(440) 0.200 0.090 - 0.096 Detector
Aperture 25mm x 100mm 2-D spatial resolution
lt 0.1mm Candidate detectors Advanced solid
state e.g. CCD, or advanced gas detector e.g.
GEM.
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• 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 gt100 resolvable
  lines of sight
• Horizontal resolution 0.1 mm
• QDE / Energy range gt 0.7, 6 13 keV (Uport
  also 3 6 keV)
• Average count rate density 106 count/cm2.s
• Peak count rate density 107 count/cm2.s
• n-? background count density 104 count/cm2.s
• (flux of 106 n-?/cm2.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.

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• 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.

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• 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 lt f-Kr lt 10-4.
• Uses a modest instrument sensitivity of 1.4 .
  10-7 cm2 per chord. (10x higher is possible).

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• 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 gt 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).