Transcript T Nakano

3Sep2013
ADAS Workshop
Badhonnef, GE
W transport studies in JT-60U
T. Nakano
Japan Atomic Energy Agency
Tungsten: a candidate for PFCs in reactors
T~104 eV
n~1020 m-3
Wq+
(q~40-60)
W divertor plates
Tungsten:
suitable for plasma facing components
for reactors
High melting point
Low fuel retention
Low sputtering yield (long life time)
Unsuitable
Highly radiative
Narrow operation window as PFCs
( TDBTT< T <Trecrystalliation)
Neutron damage ( transformation, etc )
Present study:
 Suppression of W accumulation
W divertor plates in JT-60U
W coated CFC tiles:
50 m with Re multi-layer
11 tiles (1/21 toroidal length )
Inner
Div.(C)
Dome
(C)
Standard configuration
W tile
W exp. configuration
Outer
Div.(C)
W tile
Diagnostics
 Short-wavelength VUV spectrometer
–
( 0.5- 40 nm )
On-axis : W XLVI intensity (core)
 Long-wavelength VUV spectrometer
( 20 – 120 nm )
Off-axis: sensitivity calibration
 Visible spectrometer
– sensitivity calibration




PIN
Soft X-ray (>3keV)
CXRS
Toroidal rotation
TMS
Te, ne
FIR, CO2 line density
Identification of VUV spectrum (on-axis)
Steps of spectral analysis:
1. Wq+ spectrum <= FAC*
2. Adjust Fractional
Abundance (FA)
3. Wq+ spectrum x FA
4. Sum-up
5. Comparison with
observed spectrum
•W41+ - W52+ were identified
•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density
*) M.F.Gu, Can. J. Phys. 86 (2008) 675. http://sprg.ssl.berkeley.edu/~mfgu/fac/
59+
n
3p
6.11 W
58+
5.98 W
57+
5.85 W
56+
5.74 W
55+
5.35 W
54+
5.21 W
53+
5.06 W
4.92 W
51+
19
4x10 m
8 keV
-3
52+
n
3d
4.71 W
50+
4.58 W
49+
4.44 W
48+
4.30 W
47+
4.17 W
46+
4.05 W
19
4x10 m
4 keV
-3
45+
4s
n
2.41 W
44+
2.35 W
3s1/2 - 3p1/2
(Si)
(P)
(S)
(Cl)
(Ar)
3p3/2 - 3d3/2
60+
(Al)
(K)
(Ca)
(Sc)
(Ti)
(V)
(Cr)
(Mn)
(Fe)
(Co)
4s1/2 - 4p3/2
19
6.59 W
(Mg)
3p3/2 - 3d5/2
-3
6.73 W
4x10 m
12 keV
61+
3s1/2 - 3p3/2
62+
7.00 W
3p1/2 - 3d3/2
n
3l - 4l
3s
IP (keV)
63+
7.13 W
(Na)
(Ni)
(Cu)
(Zn)
0
1
2
3
4
5
Wavelength (nm)
6
7
8
9
* ¼ picsFWHM
0.5 keV
4x1019 m-3
Identification of VUV spectrum (on-axis)
Steps of spectral analysis:
1. Wq+ spectrum <= FAC*
2. Adjust Fractional
Abundance (FA)
3. Wq+ spectrum x FA
4. Sum-up
5. Comparison with
observed spectrum
•W41+ - W52+ were identified
•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density
*) M.F.Gu et al., Astrophys. J. 582 (2003) 1241. http://sprg.ssl.berkeley.edu/~mfgu/fac/
Evaluation of W44+ ionization / W45+ recombination rate
Excitation rate
Measurement
I W45+(6.2 nm): 4s 2S1/2 - 4p 2P3/2 = Ce45+ (4s, 4p)· nW45+ (4s)· ne
1S
1P
I W44+(6.1 nm): 4s4s *)
4s4p
0
C P Ballance J.1 Phys. B 40 (2007) 247
ORNL*
Close
energy1 (199LLNL,
ev andFAC,
204 eV)
44+excitation
21
45+: 4s 2 S 0 - 4s4p
2 P 1, 205 eV, 204 eV, 205 eV
W
Similar
dependence
of C199
W
: 4senergy
S1/2 - 4p
P3/2, 201 eV,
eV, 200 eV
e
W
10
10
45+
W
1.0
45+
W
-10
10
44+
/W
~ 0.44
-11
10
1
10
2
3
10
Te ( eV )
10
4
0.5
0.0
Ratio of Excitation rates
44+
-9
S 44+®45+
(Ioniz.rate)
LANL ~
1.50.44· 45+®44+
a (Recomb.rate)
FAC
ORNL
Calculation
-8
3
Excitation rate ( cm / s )
10
Ioniz. Equi.
E048141
NB
Te ( keV )
0.0
5
EC
0
Te
ne
10
5
-3
0.5
10
6
19
IP
3
ne ( 10
1.0
15
0.3
12
0.2
8
0.1
4
W44+
5
~50+
W44+
Ratio
W
I
1
/I
W45+
,I
W
45+
W
,I
W50+
I
Negative shear discharge
-W accumulation occurs
 Te decrease
from 10 keV to 5 keV
 During Te decrease,
IW45+ and IW44+ increases,
and then decreases
0.0
44+
W45+
SX ( ch )
0
(a.u.)
Ip ( MA )
1.5
m ) PNB, PEC ( MW )
Waveform of Negative Shear discharge
with EC injection
0
4
6
8
Time ( s )
10
120
Te -scan data for
W45+ / W44+
 Comparison with
ionization equilibrium
100
Cal:
nW45+ / nW44+
= S44+ / a 45+
10
Density ratio ( W
45+
/W
44+
)
FAC calculation reproduced measured W45+/W44+
Exp:
nW45+ / nW44+
= I45+ / I44+ / 0.44
1
FAC
0.1
10
3
2
JT-60U experiment
3
Te ( eV )
4
5
6
7
8 9
10
4
Accuracy of ionization/recombination rates calculated
with FAC were evaluated in JT-60U experimental data
Waveform of W accumulation shot
Ctr
Co
Switch Co. to Ctr NBs.
With decreasing VT, W
XLVI increases, while W I is
constant.
 W accumulation
The same phase
between W XLVI and SX(5)
W XLVI is a measure
inside the Sawtooth layer
Systematic experiments on W accumulation against VT
were performed
Plasma rotation and central heating effective in
avoiding W accumulation
nW / ne
10
-3
Radiation collapse
3%
10
10
-4
-5
-200
Neutral Beam
-100
0
Plasma rotation velocity ( km / s )
T. Nakano and the JT-60 team, J. Nucl. Mater. S327 (2011) 415.
100
3
Radative power rate ( W cm )
Radiative power rates calculated with FAC
10
-24
Lw*
Lw = ! q LWq+ Fa(q)
4f
10
25+ - 27+
W38+ - 45+
W
28+ - 37+
W
46+
W
-25
64+
W
10
70+
-26
10
2
2
4
6 8
10
3
2
4
6 8
10
4
2
4
W
63+
W
Te ( eV )
Radiative power ( line radiation ) is highest between 2 – 4 keV
Dominant charge states change at Te ~ 4 keV
from highly raditive n=4-shell to lowly radiative n=3-shell
Decrease of Lw
*T Putterich et al Nucl. Fusion 50 (2010) 025012
3
Radative power rate ( W cm )
Comparison of calculated radiative power rate
with NLTE5 workshop results**
10
10
10
-24
Lw*
Lw = ! q LWq+ Fa(q)
-25
-26
10
2
2
4
6 8
10
3
2
4
6 8
10
4
2
4
Te ( eV )
FAC calculation is in agreement with the NLTE5 results
*T Putterich et al Nucl. Fusion 50 (2010) 025012
**Y Ralchenko et al AIP Proceedings 1161 (2009) 242
Radiative power from W ( MW )
Evaluated radiative power
in agreement with bolometoric measurement
1
Radiation collapse
DPBOL = Pbefore – Pafter
0.1
PNB = 15 MW
Pradcore ~ 4 MW
0.01
(Te ~ 5 – 6 keV )
-200
-100
0
100
Toroidal rotation velocity at ! =0.05 ( km / s )
Negative Feed-Back seems to result in radiation collapse:
W accumulation => Radiation increase => Te decrease =>
Lw increase
=> Radiation increase => …
Summary and Conclusions
W XLVI ( 6.2 nm ) intensity was measured with
absolutely calibrated VUV spectrometers.
Validity of Ioniz./Recomb. rate calculated with FAC was
confirmed from W45+/W44+ density ratio
under ionization equilibrium with coronal model.
Quantitative measurement of
-W density: ~ 10-3 in W accumulation cases.
>> ITER allowable level (10-5).
-W radiative power: agrees with bolometoric measurement
Thank you!
Intensity (a.u.)
W63+(3s-3p,3p-3d) at 2 nm identified in JT-60U*
0.8
(a)
55+~61+
W
O
JT-60U
60+~63+
(3s-3p)
5+
identified in EBIT**
were reproduced by
the FAC calculation.
 3s-3p at 2.3 nm
 3p-3d at 2 nm
43+~45+
C
0.4
EBIT(NIST)** 3s-3p lines at 7-8 nm
W
(3p-3d)
7+
E049786
W
(4s-4p)
13 keV
12 keV
3 keV
0.0
65+
F-like W
64+
Ne-like W
63+
Na-like W
62+
Mg-like W
61+
Al-like W
60+
Si-like W
59+
P-like W
58+
S-like W
57+
Cl-like W
56+
Ar-like W
55+
K-like W
54+
Ca-like W
q
Synthesized 65
(b)
The W63+ line
2
3
(c)
n
2p
64
n
63
3s
62
61
60
59
n
3p
58
57
at 2.3 nm will
be a good
diagnostic
line
Calculated
by FAC
56
n
55
for ITER high
temperature
12 keV,
4x1019 m-3 plasma.
3d
54
4
5
6
Wavelength ( nm )
7
* J. Yanagibayashi, T. NakanoWavelength
et al., accepted(nm)
to J. Phys. B
**Y. Ralchenko et al J. Phys. B 41 (2008) 021003
8
9
0
10 20
Assumed Fractional
Abundance (%)
Neutral Beam injectors
• 11 positive-ion-based NBs (PNBs~85keV)
• 2 co-tangential NB, 2ctr-tangential NBs, and 7 perp. NBs.
 Combination of tangential and perpendicular NBs leads to
wide range of toroidal rotation.
2 ctr-tang. PNBs
(~4.5MW)
7 perp. PNBs
(~15.75MW)
21
2 co-tang. PNBs (~4.5MW)
Comparison of time scales of atomic process:
Colonal model is valid
W45+
n=5
4f
4d
4p
3d104s
Ionization
Radiative transition
4.4x1011 s-1
Excitation
3
3d10
Rate coefficient ( m / s )
-14
W46+
10
Excitation: W
-15
10
-16
-17
(4p) -> n=4 or n=5
7.8x10-16
10
10
45+
Ionization: W
45+
(4p) -> W
46+
1.2x10-17
-18
10
-19
10
10
tRadiative
tExcitation
tIonization

3
5 keV
4
10
Te ( eV )
= 1 / 4.4x1011
= 2.3x10-12 s
= 1 / 7.8x10-16 4x1019 = 3.2x10-5 s
= 1 / 1.2x10-17 4x1019 = 2.1x10-3 s
tRadiative
<<
tExcitation <
tIonization
ne
Deexcitation is dominated by radiative transition
W generation
2.5
0.25%
1.5
( 10
20
-2
-1
m s )
2.0
W generation flux
0.4%
Te~ 20 eV
0.1%
1.0
0.5
0.0
0
2
8
6
4
22
-2
10
-1
Ion flux ( 10 m s )
W sputtering yield against D ~ 0.25% ( too high )
Possible W sputtering mechanisms
• by impurity ( C )
• by high energy particles during ELM
High energy particles seem a key for W sputtering
Te~ 20 eV
Time average ~ 1 s
 With decreasing VT,
Yphys.decreases
while Te increases
 Opposite trend
 Needs ELM-resolved
data
 With decreasing VT,
ELM frequency becomes
high and DWdia decreases*
Similar trend
between Yphys. and DWdia
W sputtering is possibly
due to high energy particles
expelled during ELM
*) K.Kamiya et al., Plasma Phys. Control.
Fusion 48 (2006) A131.
Tungsten in Fusion Research
Tungsten as a plasma-facing component
Merit : high melting point => compatible with high temperature fusion plasma
: low hydrogen (T) retention => safety, economy
: low sputtering yield => long lifetime
Cross section of ITER
: low dust production
Demerit : high Z (74)
 highly radiative ( allowable nW/ne < 10-5)
 accumulation in the core plasma
W
Plasma
Issues of W transport study
Understanding of
Transport in core plasma*
=> accumulation mechanism in core plasma
Local transport in divertor, global migration,,,
Control of
W generation, W penetration, W accumulation,,,
Preparation of diagnostics at high Te ~ 15 keV ( ~ Wq+ : q > 60)
Evaluation of W density, W ion distribution*, radiative power,,,
Divertor
*present study
Requirement for W atomic data
=>calculation with an atomic structure code,FAC*
① 二電子性再結合断面積の計算
② JT-60U, LHD スペクトルの解析
*) M.F.Gu et al., Astrophys. J. 582 (2003) 1241. http://sprg.ssl.berkeley.edu/~mfgu/fac/
Significant difference in Ionization equilibrium
Fractional Abandance
1
44+
0.1
46+
45+
0.01
FLYCHK code
Fractional Abandance
0.001
1
0.1
0.01
AUG*
LLNL code
0.001
10 3
10
3
10 4
103
10
104
4
)
TTe( (eVeV
)
e
Te ( eV )
Atomic data ( Ioniz./Recomb. rates ) are still to be checked
 Atomic code calculation with FAC
 Experimental validation in JT-60U plasmas
*T Putterich et al Plasma Phys. Control. Fusion 50 (2008) 085016
Ionization equilibrium:
Difference between AUG* and FAC calculation
Fractional Abundance
Fractional Abundance
1
Still different:
Shift to lower Te
in AUG calculation
0.1
0.01
Ionization equilibrium:
Sq+=>(q+1)+ ･nWq+
= a (q+1)+=>q+ ･nW(q+1)+
AUG*
1
45+ 46+
44+
4
2
0.1
S = Sdirect + Sexcit.autoioniz.
a = aradiative + adie-electronic
4
2
0.01
4
2
0.001 5
*present study
FAC
6 7 8 9
10
3
2
3
4
5
6 7 8 9
10
4
Te ( eV )
*T Putterich et al Plasma Phys.
Control. Fusion 50 (2008) 085016
10
3
Ionization & recomb. rate ( m / s )
Accurate recombination rates required
=> Calculated with FAC
-15
10
10
10
-16
-17
ADPACK mod**
45+
44+
W -> W
Loch Ioniz.*
FAC DR.
FAC Ioniz.
4d nl
44+
45+
W
->
W
4p nl
FAC RR.
4s nl
5d nl
5p nl
-18
10
2
Ionization
10
3
4
10
10
Te ( eV )
Te ( eV )
5
Present
Ref**
FAC (DW)
Loch code* (DW)
W44+-46+ : FAC
Dielectronic Recombination
the others: ADPACK mod.
Radiative Recombination
10
6
FAC
ADPACK mod.
( x 0.39 )
*S Loch et al., Phys. Rev. A 72 (2005) 052716 **T Putterich et al., Plasma Phys. Control. Fusion 50 (2008) 085016
W confinement time: ~ 0.5 s inside sawtooth layer
Present work: nWtotal = I WXLVI / Cexcite / ne / FFA(45+) / r ST ( m-3 )
GW = S/XB * I WI
( 1/s )
 tW = nWtotal * VpST / GW ( s )
I W XLVI / I WI ne(0) ( a.u.)
Significant W accumulation at negative toroidal rotation*
Previous work*: W accumulation was evaluated in A.U.
*) T. Nakano et al., Nucl. Fusion 49 (2009) 115024.
Calculation model: Example for W 15+
Electron configuration:
4d10 4f11 5s2
4d10 4f11 5s1 5*1;5s=0
4d10 4f12 5s1
4d10 4f11 5s1 6*1
4d9 4f12 5s2
Atomic structure
calculation
Energy level:
Excitation rate:
Radiative transition
rate:
Coronal model
Population normalized at the ground level
Calculation model: Example for W 15+
4d10 4f11 5s2Electron configuration:
(Ground state)
4d10 4f11 5s2
4d10 4f11 5s1 5*1;5s=0
4d10 4f12 5s1
4d10 4f11 5s1 6*1
4d9 4f12 5s2
Excitation
Radiative transition
 Coronal model
4d9 4f12 5s2
Term Energy ( eV )
Calculated W spectra
JT-60U peripheral plasma: two peaks needed
41+ - 44+
26+ - 36+
W
W
35+ - 43+
C
1
W
Intensity (a.u.)
4+
E049540 t=7-8s
Observed
Synthesized
0
D n =0
(n =3)
Co-like
Ni-like
No Dn =0 transitions
q of W
q+
45
Ge-like
40
D n =0
(n =4)
Rb-like
35
Mo-like
T e = 2 keV
19
ne = 3 x10
4
5
6
Wavelength (nm)
)
* T. Nakano et al., Nucl. Fusion 49 (2009) 115024.
30
m
-3
Ag-like
7 0.0 0.1 0.2 0.3
Fractional Abundance
Contents
 Introduction
 Experimental set-up/Diagnostics
- Absolute calibration of VUV spectrometers
 Results
- Evaluation of Ionization equilibrium
- Quantitative evaluation of
W confinement time, density, radiative power
- W generation
 Conclusions
2
ph / sr m nm s )
Intensity ( a.u. )
Intensity ( a.u. )
Intensity ( a.u. )
( 10
18
Intensity
Sensitivity Calibration of VUV spectrometers:
“ Triple” Branching ratio method
1.0
2
2
2
C IV 3s S - 3p P
Visible
2
C II 2p P - 3d D
0.5
0.0
400
500
500
250
2
600
Wavelength ( nm )
2
C IV 2s S - 3p P
30
50
Wavelength ( nm )
5
10
O VIII ( 1-2 )
15
20
Wavelength ( nm )
60
70
5
10
15
20
Wavelength ( nm )
80
Short-VUV
He II ( n=1-2 )
25
30
Short-VUV
O VIII (2-3)
0.05
2
C II 2p P - 3d D
C VI ( n=2-4 )
0.2
0.00
2
C VI (n=3-4 )
40
C VI ( n=1-4 )
0.10
Long-VUV
He II ( n=1-2 )
0
20
0.0
700
He II ( n=1-2 )
25
30
Sensitivity Calibration of VUV spectrometers:
10
10
19
W XLVI
20
C VI ( n = 1-4 )
-1
10
21
-2
-1
Sensitivity
10
Branching ratio
Coronal model
~ 1 / 4.2
He II ( n = 1-2 )
W XLVI
C VI ( n = 2-4 )
22
-1
( ph sr m s (counts pixel) )
10
18
5
10
15
20
25
30
Wavelength ( nm )
Absolute sensitivity ~ 6.2 nm was obtained
W XLVI is used for W density measurement