Modeling and Simulation of Fast Neutral Beam Sources for ...
Recent progress in neutral beam current drive …. Hopf IAEA, Vienna, 01—04 Sept. 2015...
Transcript of Recent progress in neutral beam current drive …. Hopf IAEA, Vienna, 01—04 Sept. 2015...
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Max-Planck-Institut
für Plasmaphysik
Recent progress in
neutral beam current drive experiments on
ASDEX Upgrade
C. Hopf, D. Rittich, B. Geiger, A. Mlynek, M. Reich,
A. Bock, A. Burckhart, C. Rapson, F. Ryter,
the ASDEX Upgrade and EUROfusion MST1* Teams
* See http://www.euro-fusionscipub.org/mst1
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
NBI and current drive capabilities on ASDEX Upgrade
Versatile NBI system 8 beams, 2.5 MW each, on two injectors: 2 “radial” beams @ 60 kV 2 “intermediate” beams @ 60 kV 2 “intermediate” beams @ 93 kV* 2 “tangential, off-axis CD” beams @ 93 kV*
Diagnostics ( information related to)
• Loop voltage
total driven current
• Motional Stark effect (MSE) current profile
• Fast ion D-alpha (FIDA) radial fast ion profile
• Faraday rotation polarimetry current profile • Neutron rates number, energy, radial distribution of fast ions Practical approach: Comparison to synthetic diagnostics
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Off-axis NBCD on AUG: historic inconsistencies
MSE does not fit: S. Günter et al., NF 47 (2007) 920
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H-mode, 600 kA
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Off-axis NBCD on AUG: historic inconsistencies
MSE does not fit: S. Günter et al., NF 47 (2007) 920
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H-mode, 600 kA
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Off-axis NBCD on AUG: historic inconsistencies
“non-neo-classical case”
B. Geiger, PhD thesis (2012)
S. Günter et al., NF 47 (2007) 920
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H-mode, 800 kA
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Off-axis NBCD on AUG: historic inconsistencies
“non-neo-classical case”
B. Geiger, PhD thesis (2012)
S. Günter et al., NF 47 (2007) 920
Immediate question: Are there cases where the fast ion distribution is neo-classical while the driven current does not agree with the neo-classical prediction? Simultaneous MSE and FIDA measurements needed!
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
The “new” discharge
• Continuous MSE and FIDA (beam 3 running through) • Preemptive NTM and sawtooth avoidance by ECCD • Real-time Te feedback control by RT-ECE/ECRH in off-
axis phase
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Ip = 800 kA, H-mode, #31453
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
The “new” discharge
• Continuous MSE and FIDA (beam 3 running through) • Preemptive NTM and sawtooth avoidance by ECCD • Real-time Te feedback control by RT-ECE/ECRH in
off-axis phase
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Ip = 800 kA, H-mode, #31453
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Constant Te and ne profiles
Spline-fitted profiles as input to TRANSP, Te and ne from integrated data analysis. Ti from core CXRS
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Te vs rtor
3.5 s 5.6 s
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Very little MHD activity: Some fishbones, nothing else
SXR
Magnetic Spectrum
15 kHz
on axis off axis on axis
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
TRANSP predicted currents and loop voltage
TRANSP predicts: • ≈ 95/160 kA NBCD in on/off-axis phase • no change in bootstrap current
Measured loop voltage: Agrees best with TRANSP prediction assuming no or moderate anomalous diffusion
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
TRANSP predicted currents and loop voltage
Loop voltage sensitive to Zeff Zeff profiles calculated from CXRS-derived impurity concentration profiles
Measured and calculated loop voltage agree in absolute values!
Measured loop voltage: Agrees best with TRANSP prediction assuming no or moderate anomalous diffusion
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Fast Ion D spectroscopy: radial distribution of fast ions
on axis NBI @ 3.5 s
off axis NBI
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on axis NBI @ 7.5 s
FIDA 4D fast ion distribution function from TRANSP, post-processed using FIDASIM synthetic radial intensity profiles • agrees best with 0.0–0.2 m2/s anomalous diffusion
in on-axis phases
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Fast Ion D spectroscopy: radial distribution of fast ions
on axis NBI @ 3.5 s
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on axis NBI @ 7.5 s
FIDA 4D fast ion distribution function from TRANSP, post-processed using FIDASIM synthetic radial intensity profiles • agrees best with 0.0–0.2 m2/s anomalous diffusion in
on-axis phases • unresolved discrepancy around rpol = 0.5 with off
axis NBI
off axis NBI
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Interlude: Physics-based estimates of diffusion coefficients
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M.J. Pueschel et al., NF 52 (2012) 103018
Based on gyrokinetic (GENE) simulations Pueschel at al. give approximate formulae for D describing micro-turbulent transport as function of experimentally accessible parameters: eff effective heat diffusivity
fast ion pitch angle EFI fast ion energy Te electron temperature plasma beta crit critical beta w.r.t. KBMs
Plotted values: • Energy-averaged • electrostatic and electromagnetic contributions added • finite Larmor radius approximation taken
Can be used in TRANSP as tabulated D(r, t, , E)
only for EM part
DES(r, t) + DEM(r, t) [m2/s]
rto
r
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Fast Ion D spectroscopy: radial distribution of fast ions
FIDA 4D fast ion distribution function from TRANSP, post-processed using FIDASIM synthetic radial intensity profiles • agrees best with 0.1–0.3 m2/s anomalous diffusion
in on-axis phases • unresolved discrepancy around rpol = 0.5 with off
axis NBI • Very little difference between neo-classical (D = 0),
D = 0.1 m2/s and DPueschel(r, t, E)
on axis NBI @ 3.5 s
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on axis NBI @ 7.5 s
off axis NBI
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Motional Stark effect spectroscopy: Radial current profile
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Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
sh
ifte
d
to
mat
ch
he
re
rpol = 0.12 rpol = 0.23 rpol = 0.47 rpol = 0.58 rpol = 0.68
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Motional Stark effect spectroscopy: Radial current profile
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rpol = 0.12 rpol = 0.23 rpol = 0.47 rpol = 0.58 rpol = 0.68
Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Motional Stark effect spectroscopy: Radial current profile
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rpol = 0.12 rpol = 0.23 rpol = 0.47
rpol = 0.58 rpol = 0.68
Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
Motional Stark effect spectroscopy: Radial current profile
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B. Geiger et al., PPCF 57 (2015) 014018
rpol = 0.12 rpol = 0.23 rpol = 0.47
rpol = 0.58 rpol = 0.68
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Motional Stark effect spectroscopy: Radial current profile
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rpol = 0.12
rpol = 0.23 rpol = 0.47 rpol = 0.58 rpol = 0.68
Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Motional Stark effect spectroscopy: Radial current profile
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rpol = 0.12
rpol = 0.23 rpol = 0.47 rpol = 0.58 rpol = 0.68
Comparison with MSE angles calculated from TRANSP equilibria:
• “Neoclassical” does not fit well in outer channels
• Better (best) fit: D ≈ 0.5 m2/s
• “No NBCD” does not fit well in inner channels
• DPueschel in between neo-classical and D = 0.5 m2/s
Note: Compared to previous studies • Sign of Er (TRANSP)
corrected • Corrected geometry of
beam 8
Caution! MSE not absolutely calibrated (yet). We compare only temporal evolutions from the on-/off-axis transition onwards.
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Faraday rotation polarimetry
Faraday rotation:
neBu ds
u: unit vector along LOS
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All simulations shifted by –1.6°!
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Faraday rotation polarimetry
Faraday rotation:
neBu ds
u: unit vector along LOS
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• Generally reasonable agreement with TRANSP-based simulation
• Cannot resolve between neo-classical simulation and D = 0.5 m2/s
All simulations shifted by –1.6°!
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Faraday rotation polarimetry
Faraday rotation:
neBu ds
u: unit vector along LOS
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• Generally reasonable agreement with TRANSP-based simulation
• Cannot resolve between neo-classical simulation and D = 0.5 m2/s
• No agreement w/o NBCD
All simulations shifted by –1.6°!
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Neutron rates
Unfortunately absolute measured neutron rates cannot be trusted currently. However, the relative integrated signal of the neutron spectrometer is reliable. Overall reasonable agreement. Unfortunately not sensitive to small variations of radial transport. Simulations have considerable uncertainty due to error in Zeff and H dilution of the D plasma. No conclusion supported.
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1 2 3 4 5 6 7 8 90.0
0.2
0.4
0.6
0.8
1.0
1.2
ne
utr
on r
ate
(a.u
.)
realtime
neutron spectrometer (integrated)
TRANSP neo-classical
TRANSP D = 0.5 m2/s
all rates scaled to coincide in on-axis phases
C. Hopf IAEA, Vienna, 01—04 Sept. 2015
Summary, conclusions, and outlook
Summary • Loop voltage, MSE, and Polarimetry clearly show that NBI drives a current. • FIDA during on-axis NBI compatible with no to mild (0.0–0.2 m2/s) anomalous transport • D 0.2 m2/s agrees well with “Pueschel values” • Disagreement of simulation with off-axis FIDA at medium r not understood. • Temporal evolution of MSE angles after on-/off-axis transition fits best with D 0.5 m2/s.
Conclusion Initial question: Do FIDA (radial fast ion profile) and MSE (current profile) contradict each other?
My tentative answer: We have no reason to assume so! Outlook • Diagnostics enhancements will reduce dependency on beam 3 and add redundant
information. • Absolute calibration of MSE expected soon Will allow separation of on- and off-axis
transport effects • Next step: Parameter study to find the transition from neo-classical to diffusion-dominated
regime
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C. Hopf IAEA, Vienna, 01—04 Sept. 2015
q profiles (TRANSP neo-classical)
1.85 sec (before NBI) 3.50 sec (on-axis NBI) 5.30 sec (off-axis NBI)
rtor
q
B. Geiger September 04, 2015, Fachbeirat, Greifswald 32
Comparison with TRANSP modelling
• Synthetic MSE –angles
can be calculated from
TRANP equilibria
• But offset per channel
needed for comparisons!
• Agreement with the neo-
classical simulations
(except the innermost
channel)
• Assumption of localized
anomalous fast-ion
transport has no clear
effect
• Earlier analysis: wrong
sign of Er in TRANSP and
geometry of NBI Q8 5 cm
too low
B. Geiger September 04, 2015, Fachbeirat, Greifswald 33
Improved analysis of radial MSE profiles
• Correct geometry
description of MSE LOS
allows study of radial MSE
profiles
• Bz can be determined
based on the MSE data
• -> radial current profiles
can be calculated
O. Ford
B. Geiger September 04, 2015, Fachbeirat, Greifswald 34
Change of radial current density profiles
• Relative change of the
neo-classical simulation
within the statistical error
bars of the measurement
• Similar agreement when
considering localized
anomalous transport
Petty, C et al., Nucl. Fusion 42 (2002) 1124 – 1133
• Given j~rot(B), the radial derivative of Bz is
roughly proportional to the current density