R Barnsley, Moscow, Nov 2003.1 ADAS/SANCO (Atomic data and impurity transport codes) - Evaluation of...

R Barnsley, Moscow, Nov 2003. 1

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


0.5 0.6 0.7 0.8 0.9 10

0.0002

0.0004

0.0006

0.0008

H-like ClHe-like Cl Li-like ClH-like Ar

r/a

E (w

/cm^3

)

0.7 0.75 0.8 0.85 0.9 0.95 1 1.050

0.0005

0.001

0.0015

H-like O H-like C H-like Be

r/a

E (w

/cm^3

)

0 0.2 0.4 0.6 0.8 10

0.002

0.004

0.006

H-like Fe He-like Fe Li-like Fe (x5)Ne-like Fe (x5)

r/a

E (w

/cm

^3)

0 0.2 0.4 0.6 0.8 10

0.0002

0.0004

0.0006

H-like Kr He-like KrLi-like KrNe-like Kr (x10)

r/a

E (w

/cm

^3)

ITER-98 impurity profiles


0 0.5 10

0.2

0.4

0.6

0.8

1

H-like Kr 35+ 1s-2p

Line-peak/continuum ratio for f-Kr=10^-5

r/a

0 0.5 10

1

2

3

4

He-like Kr 34+ 1s^2-1s2p

Line-peak/continuum ratio for f-Kr=10^-5

r/a

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.

0 0.2 0.4 0.6 0.8 110

0

10

20

30

Ne (10^19/m^-3) Te (keV) Ti (keV)Vtor (*10 km/s)Vpol (km/s)

ITER Reversed-Shear Profiles

r/a

ITER profiles used for SANCO and signal modelling


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.


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).


Crystal, radius R

Detector

ShieldGraphite prereflector

Input cone

Rowland circle, diameter R

Schematic of a Johann spectrometer with graphite prereflector to provideshielding and allow poloidal and toroidal components of the line of sight. Thewavelength range , and the crystal filling factor , are both determined by thesight-tube dimensions.


1.8 1.85 1.90

5 109

1 108

1.5 108

2 108

2.5 108

3 108

Graphite(001)/Ge(220) peak sensitivityGraphite(001) passband at 8.0deg Bragg angleSpectrometer passbandH-like FeHe-like FeH-like Kr (2nd order)He-like Kr (2nd order)

Wavelength (Angstrom)

Sen

siti

vity

S (

cm^2

)

Accessible spectrum and spectrometer passband, in the region of the principallines of H- and He-like Fe and Kr, for a Johann spectrometer with graphiteprereflector


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%)


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)


Multi-chord X-ray spectrometer option

ISO views of eport9


- Upper and lower systems give continous coverage of the plasma core r/a <~ 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.

Upper view

Lower view

‘L’

‘U’

Core views with continuous coverage on equatorial port 9


Two or more discreet views –graphite reflectors

Continuously resolved withimaging crystal optic

Two or more graphite reflector based lines of sight will complete plasma coverage


Option for equatorial port

- Allows continuous imaging

- Minimises blanket aperture


Imaging Multichord or Imaging

Discrete, graphite

X-ray Views Referred to Mid-plane Profiles

Approximate coverage of the combined upper-port and mid-plane x-rayarrays, 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 detector

fs/fm = -1/cos(2B)

- No real focus for B < 45°

fs: Sagittal focus fm: Meridional focus B: Bragg angle

Spherically Bent Crystal


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.


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)


T h e c o u n t - r a t e N ’ ( c o u n t / s ) f r o m a s p e c t r a l l i n e w i t h i n t e n s i t y I ( p h o t o n / c m 2 . s ) , i s g i v e n b y

N' .I S

w h e r e , f o r a J o h a n n s p e c t r o m e t e r w i t h g r a p h i t e p r e r e f l e c t o r , t h e s e n s i t i v i t y f u n c t i o nS ( c m 2 ) i s g i v e n b y

S ....Pgr

.. Rc .4

hx hy

T h e t e r m s a r e : g r a p h i t e p e a k r e f l e c t i v i t y P g r , v e r t i c a l d i v e r g e n c e ( r a d ) , c r y s t a l r e f l e c t i o ni n t e g r a l R c ( r a d ) , p r o j e c t e d c r y s t a l w i d t h h x ( c m ) , c r y s t a l h e i g h t h y ( c m ) , a n d t h e c o m b i n e dd e t e c t o r a n d w i n d o w e f f i c i e n c i e s . T h e f r a c t i o n o f t h e c r y s t a l a p e r t u r e f i l l e d a t a g i v e nw a v e l e n g t h d e p e n d s o n t h e s o u r c e a n d b e a m l i n e g e o m e t r y .


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°


Effect of input geometry on Johann sensitivity

Shield “a”

“a”

Shield “b”

Shield “c” 1 2 3

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


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 > 25mm

Ion species B range Crystal 2d (nm) range (nm)

Ar XVII / XVIII 26° -28° SiO2(1010) 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 < 0.1mm

Candidate detectors: Advanced solid state e.g. CCD, or advanced gas detector e.g. GEM.


T h e c o u n t - r a t e N ’ ( c o u n t / s ) f r o m a s p e c t r a l l i n e w i t h i n t e n s i t y I ( p h o t o n / c m 2 . s ) , i s g i v e n b y

N ' .I S

F o r a J o h a n n s p e c t r o m e t e r w i t h g r a p h i t e p r e r e f l e c t o r , t h e s e n s i t i v i t y f u n c t i o n S ( c m 2 ) i s :

S ....P g r

.. R c .4

h x h y

C r y s t a l f i l l i n g f a c t o r = 1 . T o t a l v e r t i c a l d i v e r g e n c e t o t . N o . o f v i e w i n g c h a n n e l s n c h ,

V e r t i c a l d i v e r g e n c e p e r c h a n n e l c h ( r a d ) i s :

c h = t o t / n c h

t o t ~ 0 . 5 r a d n c h = 3 5

R e f e r e n c e F e i n 1 s t o r d e r

R e f e r e n c e K r i n 2 n d o r d e r

H i g h s e n s i t i v i t y o p t i o n . O n l y K r o n g r a p h i t e ( I s t o r d e r )

G r a p h i t e p l a n e s

( 0 0 2 )

( 0 0 4 )

( 0 0 2 )

G r a p h i t e p e a k R e f l e c t i v i t y P g r

0 . 3

0 . 2

0 . 5

G e r m a n i u m c u t

( 2 2 0 )

( 4 4 0 )

( 2 2 0 )

G e r e f l e c t i o n i n t e g r a l R c

r a d

6 6

9

3 4

C r y s t a l a p e r t u r e h x , h y

c m 2

5 x 5

5 x 5

5 x 5 { 1 0 x 1 0 }

W i n d o w / d e t e c t o r e f f i c i e n c y

0 . 5

0 . 5

0 . 5 { 0 . 8 }

S D D i r e c t v i e w s

1 0 - 7 c m 2

9 . 4

1 . 3 *

4 . 7 { 3 0 }

S G r G r a p h i t e v i e w s

1 0 - 7 c m 2

2 . 8

0 . 2 5

2 . 4 { 1 5 }


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: ~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.


0 10 20 300

5000

1 104

1.5 104

2 104

2.5 104

I20 i

I215 i

I218 i

I221 i

I223 i

i

0 10 20 3010

100

1 103

1 104

1 105

Ch 0 (central chord)Ch 18Ch 22 Krypton fraction = 10^-5 Ch 24 Integration time = 100 msCh 26Ch 28Ch 35 (r/a = 1)

Simulated He-like Kr signals with noise

Detector Channel

Cou

nts

per

Cha

nnel

0 10 20 300

5000

1 104

1.5 104

2 104

2.5 104

Ch 0 (central chord)Ch 18Ch 22 Krypton fraction = 10^-5 Ch 24 Integration time = 100 msCh 26

Simulated He-like Kr signals with noise

Detector Channel

Cou

nts

per

Cha

nnel

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.


0 0.2 0.4 0.6 0.8 10.1

1

10

100

1 103

1 104

f-Kr = 10^-4, delta-Prad = 7 MWf-Kr = 10^-5, delta-Prad = 700 kWf-Kr = 10^-6, delta-Prad = 70 kWf-Kr = 10^-7, delta-Prad = 7 kW

100 ms S/N Ratio for He-like Kr 34+

r/a

S/N

rat

io

1 108

1 107

1 106

1 105

1 104

1

10

100

1 103

1 s integration time100 ms10 ms1 ms

Central-chord S/N Ratio for He-like Kr

Krypton fractional abundance

S/N

rat

io

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).


0 0.2 0.4 0.6 0.8 10

10

20

30

Ti profile (Rev shear)Chord-weighted Ti (100 ms, fKr=10^-5)

Chord-weighted Ti for He-like Kr 34+

r/a

Ti

(keV

)

0 0.2 0.4 0.6 0.8 10

50

100

150

Toroidal rotation profile (rev shear)Chord-weighted Vtor (100 ms, fKr=10^-5)

Chord-weighted Vtor for He-like Kr 34+

r/a

Vto

r (k

m/s

)

0 0.2 0.4 0.6 0.8 10

10

20

30

Ti profile (Rev shear)Chord-weighted Ti (100 ms, fKr=10^-5)

Chord-weighted Ti for H-like Kr 35+

r/a

Ti

(keV

)

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).

R Barnsley, Moscow, Nov 2003.1 ADAS/SANCO (Atomic data and impurity transport codes) - Evaluation of...

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