t. nakano japan atomic energy agency w transport studies in jt-60u 3sep2013 adas workshop badhonnef,...
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T. Nakano Japan Atomic Energy Agency
W transport studies in JT-60U
3Sep2013ADAS Workshop
Badhonnef, GE
Tungsten:suitable for plasma facing components
for reactors
High melting pointLow fuel retentionLow sputtering yield (long life time)
UnsuitableHighly radiativeNarrow operation window as PFCs
( TDBTT< T <Trecrystalliation)Neutron damage ( transformation, etc )
Tungsten:suitable for plasma facing components
for reactors
High melting pointLow fuel retentionLow sputtering yield (long life time)
UnsuitableHighly radiativeNarrow operation window as PFCs
( TDBTT< T <Trecrystalliation)Neutron damage ( transformation, etc )
Present study: Suppression of W accumulationPresent study: Suppression of W accumulation
T~104 eVn~1020 m-3
Wq+
(q~40-60)Transport
W divertor plates
Tungsten: a candidate for PFCs in reactors
W divertor plates in JT-60UW coated CFC tiles:
50 m with Re multi-layer
11 tiles (1/21 toroidal length )
W tiles
W tilesDome
(C)
Dome(C)
Inner Div.(C)
Inner Div.(C)
OuterDiv.(C)
OuterDiv.(C)
Standard configuration
W tileW tile
W tileW tile
W exp. configuration
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
*) M.F.Gu, Can. J. Phys. 86 (2008) 675. http://sprg.ssl.berkeley.edu/~mfgu/fac/
Identification of VUV spectrum (on-axis)
•W41+ - W52+ were identified•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density•W41+ - W52+ were identified•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density
1. Wq+ spectrum <= FAC*2. Adjust Fractional
Abundance (FA)3. Wq+ spectrum x FA 4. Sum-up5. Comparison with
observed spectrum
Steps of spectral analysis:
0.5
keV
4x10
19 m
-3
* ¼ picsFWHM
*) M.F.Gu et al., Astrophys. J. 582 (2003) 1241. http://sprg.ssl.berkeley.edu/~mfgu/fac/
Identification of VUV spectrum (on-axis)
•W41+ - W52+ were identified•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density•W41+ - W52+ were identified•Isolated W45+ line (W XLVI) at 6.2 nm is used for W density
1. Wq+ spectrum <= FAC*2. Adjust Fractional
Abundance (FA)3. Wq+ spectrum x FA 4. Sum-up5. Comparison with
observed spectrum
Steps of spectral analysis:
I W45+(6.2 nm): 4s 2S1/2 - 4p 2P3/2 =
Excitation rate
I W44+(6.1 nm): 4s4s 1S0 - 4s4p 1P1
Close excitation energy (199 ev and 204 eV)Similar energy dependence of Ce
Close excitation energy (199 ev and 204 eV)Similar energy dependence of Ce
~ 0.44 (Ioniz.rate)
(Recomb.rate)
Ioniz. Equi.
Calculation
Measurement
Evaluation of W44+ ionization / W45+ recombination rate
Waveform of Negative Shear discharge with EC injection
Negative shear discharge-W accumulation occurs
Te decrease from 10 keV to 5 keV
During Te decrease, IW45+ and IW44+ increases, and then decreases
Te -scan data for W45+ / W44+
Comparison with ionization equilibrium
Te -scan data for W45+ / W44+
Comparison with ionization equilibrium
ECNB
IP
Te
ne
FAC calculation reproduced measured W45+/W44+
Accuracy of ionization/recombination rates calculated with FAC were evaluated in JT-60U experimental data
Accuracy of ionization/recombination rates calculated with FAC were evaluated in JT-60U experimental data
Cal:nW
45+ / nW44+
= S44+ / 45+
Exp:nW
45+ / nW44+
= I45+ / I44+ / 0.44
Waveform of W accumulation shot
Switch Co. to Ctr NBs.With decreasing VT, W XLVI increases, while W I is constant. W accumulationThe 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
Systematic experiments on W accumulation against VT were performed
Ctr
Co
Neutral Beam
Plasma rotation and central heating effective in avoiding W accumulation
T. Nakano and the JT-60 team, J. Nucl. Mater. S327 (2011) 415.
3%
Radiation collapse
Radiative power ( line radiation ) is highest between 2 – 4 keVDominant charge states change at Te ~ 4 keV from highly raditive n=4-shell to lowly radiative n=3-shellDecrease of Lw
Radiative power ( line radiation ) is highest between 2 – 4 keVDominant charge states change at Te ~ 4 keV from highly raditive n=4-shell to lowly radiative n=3-shellDecrease of Lw
Radiative power rates calculated with FAC
4f4f
*T Putterich et al Nucl. Fusion 50 (2010) 025012
Comparison of calculated radiative power rate with NLTE5 workshop results**
FAC calculation is in agreement with the NLTE5 resultsFAC calculation is in agreement with the NLTE5 results
**Y Ralchenko et al AIP Proceedings 1161 (2009) 242*T Putterich et al Nucl. Fusion 50 (2010) 025012
Evaluated radiative power in agreement with bolometoric measurement
PBOL = Pbefore – Pafter
PNB = 15 MWPrad
core ~ 4 MW(Te ~ 5 – 6 keV )
Negative Feed-Back seems to result in radiation collapse:W accumulation => Radiation increase => Te decrease => Lw increase => Radiation increase => …
Negative Feed-Back seems to result in radiation collapse:W accumulation => Radiation increase => Te decrease => Lw increase => Radiation increase => …
Radiation collapse
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!
W63+(3s-3p,3p-3d) at 2 nm identified in JT-60U*
Calculated by FAC12 keV, 4x1019 m-3
JT-60U
Wavelength ( nm )* J. Yanagibayashi, T. Nakano et al., accepted to J. Phys. B**Y. Ralchenko et al J. Phys. B 41 (2008) 021003
EBIT(NIST)** 3s-3p lines at 7-8 nm identified in EBIT** were reproduced by the FAC calculation. 3s-3p at 2.3 nm 3p-3d at 2 nm
3s-3p lines at 7-8 nm identified in EBIT** were reproduced by the FAC calculation. 3s-3p at 2.3 nm 3p-3d at 2 nm
The W63+ line at 2.3 nm will be a good diagnostic line for ITER high temperature plasma.
The W63+ line at 2.3 nm will be a good diagnostic line for ITER high temperature plasma.
2 co-tang. PNBs (~4.5MW)21
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.
7 perp. PNBs(~15.75MW)
2 ctr-tang. PNBs(~4.5MW)
3d104s
3d10
Radiative = 1 / 4.4x1011 = 2.3x10-12 sExcitation = 1 / 7.8x10-16 4x1019 = 3.2x10-5 sIonization = 1 / 1.2x10-17 4x1019 = 2.1x10-3 s
Radiative << Excitation < Ionization
Radiative = 1 / 4.4x1011 = 2.3x10-12 sExcitation = 1 / 7.8x10-16 4x1019 = 3.2x10-5 sIonization = 1 / 1.2x10-17 4x1019 = 2.1x10-3 s
Radiative << Excitation < Ionization
Comparison of time scales of atomic process:Colonal model is valid
4p
n=5
4d4f
Exc
itatio
n
Ioni
zatio
nR
adia
tive
tran
sitio
n 4.
4x10
11 s
-1
1.2x10-17
7.8x10-16
5 keVW45+
W46+
nene
Deexcitation is dominated by radiative transitionDeexcitation is dominated by radiative transition
W generation
W sputtering yield against D ~ 0.25% ( too high )Possible W sputtering mechanisms
• by impurity ( C )• by high energy particles during ELM
W sputtering yield against D ~ 0.25% ( too high )Possible W sputtering mechanisms
• by impurity ( C )• by high energy particles during ELM
Te~ 20 eV
High energy particles seem a key for W sputtering
Te~ 20 eV With decreasing VT, Yphys.decreases while Te increases Opposite trend Needs ELM-resolved
data With decreasing VT, ELM frequency becomes high and Wdia decreases*Similar trend between Yphys. and Wdia
Time average ~ 1 s
W sputtering is possibly due to high energy particles expelled during ELM
W sputtering is possibly due to high energy particles expelled during ELM
*) K.Kamiya et al., Plasma Phys. Control. Fusion 48 (2006) A131.
Tungsten as a plasma-facing componentMerit : high melting point => compatible with high temperature fusion plasma
: low hydrogen (T) retention => safety, economy: low sputtering yield => long lifetime: low dust production
Demerit : high Z (74) highly radiative ( allowable nW/ne < 10-5) accumulation in the core plasma
Issues of W transport studyUnderstanding of
Transport in core plasma* => accumulation mechanism in core plasmaLocal transport in divertor, global migration,,,
Control ofW 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,,,
Tungsten in Fusion Research
Cross section of ITER
W Plasma
Divertor
*present study
*) M.F.Gu et al., Astrophys. J. 582 (2003) 1241. http://sprg.ssl.berkeley.edu/~mfgu/fac/
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
Significant difference in Ionization equilibrium
Te ( eV )Te ( eV )103 104103 104
FLYCHK code
LLNL code
*T Putterich et al Plasma Phys. Control. Fusion 50 (2008) 085016
Atomic data ( Ioniz./Recomb. rates ) are still to be checked Atomic code calculation with FAC Experimental validation in JT-60U plasmas
Atomic data ( Ioniz./Recomb. rates ) are still to be checked Atomic code calculation with FAC Experimental validation in JT-60U plasmas
44+45+
46+
AUG*
Ionization equilibrium:Difference between AUG* and FAC calculation
*T Putterich et al Plasma Phys. Control. Fusion 50 (2008) 085016
Still different:Shift to lower Te
in AUG calculation
1
0.1
0.01
44+
45+ 46+
Fra
ctio
nal A
bund
ance
AUG*
FAC
Ionization equilibrium:Sq+=>(q+1)+ ・ nW
q+ = (q+1)+=>q+ ・ nW
(q+1)+
S = Sdirect + Sexcit.autoioniz.
= radiative + die-electronic
*present study
*S Loch et al., Phys. Rev. A 72 (2005) 052716 **T Putterich et al., Plasma Phys. Control. Fusion 50 (2008) 085016
Accurate recombination rates required=> Calculated with FAC
Present Ref**
Ionization FAC (DW) Loch code* (DW)
Dielectronic RecombinationW44+-46+ : FACthe others: ADPACK mod. ADPACK mod.
( x 0.39 )Radiative Recombination FAC
Te ( eV )
W confinement ti
me:
~
0.5 s inside sawtooth layer
Present work: nWtotal = I WXLVI / Cexcite / ne / FFA(45+) / r
ST ( m-3 )W = S/XB * I WI ( 1/s )
W = nWtotal * Vp
ST / W ( s )
Present work: nWtotal = I WXLVI / Cexcite / ne / FFA(45+) / r
ST ( m-3 )W = S/XB * I WI ( 1/s )
W = nWtotal * Vp
ST / W ( s )
*) T. Nakano et al., Nucl. Fusion 49 (2009) 115024.
Significant W accumulation at negative toroidal rotation*
Previous work*: W accumulation was evaluated in A.U.Previous work*: W accumulation was evaluated in A.U.
I W X
LVI /
I W
I n e
(0)
( a.
u.)
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
Coronal model
Excitatio
n
Excitatio
n
Radiative
transitio
nRadiative
transitio
nAtomic structurecalculation
Energy level:
Excitation rate:Radiative transition rate:
Calculation model: Example for W 15+
Term Energy ( eV )Pop
ulat
ion
norm
aliz
ed a
t th
e gr
ound
leve
l
4d9 4f12 5s2
4d10 4f11 5s2 (Ground state)
Electron configuration:
4d10 4f11 5s2
4d10 4f11 5s1 5*1;5s=0
4d10 4f12 5s1
4d10 4f11 5s1 6*1
4d9 4f12 5s2ExcitationRadiative transitionCoronal model
Calculated W spectra
JT-60U peripheral plasma: two peaks needed
*) T. Nakano et al., Nucl. Fusion 49 (2009) 115024.
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
Long-VUV
Visible
Sensitivity Calibration of VUV spectrometers:“ Triple” Branching ratio method
Short-VUV
Short-VUV
Sensitivity Calibration of VUV spectrometers:
Absolute sensitivity ~ 6.2 nm was obtainedW XLVI is used for W density measurementAbsolute sensitivity ~ 6.2 nm was obtainedW XLVI is used for W density measurement