impact of localized ecrh on nbi and icrh driven alfven … · 2015. 9. 3. · aug #31545, ecrh #4...
TRANSCRIPT
Impact of Localized ECRH on NBI and
ICRH Driven Alfven Eigenmodes in the
ASDEX Upgrade TokamakM. Garcia-Munoz
M. A. Van Zeeland, S. Sharapov, Ph. Lauber, J. Ayllon, I. Classen, G. Conway,
J. Ferreira, J. Galdon, B. Geiger, N. Lazanyi, F. Nabais, V. Nikoleva, D. C. Pace,
L. Sanchis-Sanchez, A. Snicker, J. Stober, M. Weiland and the ASDEX Upgrade Team
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 2
DIII-D Observations Showed ECRH Can Have a
Major Impact on NBI Driven AE Stability
M. A. Van Zeeland et al., PPCF 50 035009 (2008)
Localized ECRH has
strong impact on
RSAEs
• With on-axis ECRH
deposition, strong
RSAEs are observed
• With near qmin ECRH
deposition, RSAEs are
mitigated
• TAEs still unstable
though weaker
• Mitigation mechanism
still under investigation
(ITPA EP-7)
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 3
Localized ECRH has
strong Impact on
RSAEs
• With on-axis ECRH
deposition, strong
RSAEs are observed
• With near qmin ECRH
deposition, RSAEs are
mitigated
• TAEs still unstable
though weaker
• Mitigation mechanism
still under investigation
(ITPA EP-7)M. A. Van Zeeland et al., PPCF 50 035009 (2008)
DIII-D Observations Showed ECRH Can Have a
Major Impact on NBI Driven AE Stability
• Investigate impact of localized ECRH on
both NBI and RF tail driven Alfven
Eigenmodes
Check reproducibility of DIII-D result on
NBI driven modes
Extend studies to RF tail driven modes
to test sensitivity to underlying
distribution function
• Document change in AE stability with
ECRH injection location and EP distribution
• Document resultant change in EP profiles
and EP transport
• Model ECRH impact on AE stability and
associated transport
Goal of AUG Experiments
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 4
AUGECRH Near qmin#31545
AUG
AUG
ECRH Near Axis #31541
AUG
RSAEs
BAAEs
ECE Spectrogram Near qmin
Outline
• Introduction and Motivation
• Impact of localized ECRH
on NBI Driven AEs
• Impact of localized ECRH
on ICRH Driven AEs
• Modeling of Experimental
Observations
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 5
Outline
• Introduction and Motivation
• Impact of localized ECRH
on NBI Driven AEs
• Impact of localized ECRH
on ICRH Driven AEs
• Modeling of Experimental
Observations
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 6
AUG
Early NBI and ECRH Heating Used to Create Reversed
Magnetic Shear and Drive Alfven Eigenmode Activity
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 7
• Beam (60kV) and ECRH heating begin t~0.2s
~rqmin
AUG
• Beam (60kV) and ECRH heating begin t~0.2s
• ECH deposition location scanned in series of
discharges (positions 1-5)
Early Beam and ECRH Heating Used to Create Reversed
Magnetic Shear and Drive Alfven Eigenmode Activity
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 8
• Maintaining a
repeatable density
essential for isolating
physics changing
mode stability
• Low density important
for EP population and
mode drive
Low and Reproducible Density from Discharge
to Discharge
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 9
AUG #31541, ECRH #1 (Near Axis)
AUG
With ECRH Near Magnetic Axis Broad
Spectrum of RSAE, TAE, and BAAE Driven
• Clear RSAE
activity as qmin
evolves
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 10
RSAEs
RSAEs
RSAEs
BAAEs
ECE R~1.81m
ECE R~1.86m
ECE R~1.90m
• Some MHD events
visible
• q-profile still reversed as
low-level RSAEs appear
again later
• Drastic changes like this
in mode stability provide
excellent tests for
simulations – validation
AUG #31545, ECRH #4 (Near qmin)
AUG
Early Beam Heating With ECRH Near Mid-Radius
(~qmin) Had Much Reduced AE Activity
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 11
ECE R~1.81m
ECE R~1.86m
ECE R~1.90m
Reflectometer Confirms Large Change in AE
Stability Between ECRH Near-Axis and Near qmin
ECRH Near qmin
ECRH Near Axis
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 12
Discharges with Suppressed RSAE Activity
Show Classical Fast-Ion Profiles
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 13
AUGECRH Near qmin#31545
AUG
AUG
ECRH Near Axis #31541
AUG
RSAEs
BAAEs
ECE Spectrogram Near qmin
Outline
• Introduction and Motivation
• Impact of localized ECRH
on NBI Driven AEs
• Impact of localized ECRH
on ICRH Driven AEs
• Modeling of Experimental
Observations
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 14
• All RF discharges had
same startup until
t=0.6s
on-axis ECRH and
constant beam
• After t=0.6s
ICRH (fundamental
Hydrogen minority)
NBI blips for
diagnostics
Gyrotrons that are
scanned radially from
shot to shot
On-axis ECH
ECH location varies shot to shot
AUG
RF-Tail Driven AE Portion of Experiment Also Used Early
On-axis ECRH and Beams to Create Reversed Shear
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 15
RF-Tail Drives TAEs Preferentially and ECRH Impact
on Modes is Not the Same as NBI Driven AEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 16
• At switch to ICRH,
TAEs become unstable
• BAAEs? also observed
at very low frequency
(low rotation)ICRH + ECRH On-axis
TAEs
RSAEs
#31567AUG
ECE R~1.86m
RF-Tail Drives TAEs Preferentially and ECRH Impact
on Modes is Not the Same as NBI Driven AEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 17
• At switch to ICRH,
TAEs become unstable
• BAAEs? also observed
at very low frequency
(low rotation)
• Switch to ECRH near
qmin produces little
change of RF driven
TAEs
ICRH + ECRH On-axis
ICRH + ECRH near qmin
TAEs
RSAEs
TAEs
RSAEs
#31567
#31569
AUG
ECE R~1.86m
ECE R~1.86m
RF-Tail Drives TAEs Preferentially and ECRH Impact
on Modes is Not the Same as NBI Driven AEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 18
• At switch to ICRH,
TAEs become unstable
• BAAEs? also observed
at very low frequency
(low rotation)
• Switch to ECRH near
qmin produces little
change of RF driven
TAEs
• With ECRH near qmin,
RSAEs also appear
during ICRH phase
• FILD measures TAE
induced losses
ICRH + ECRH On-axis
ICRH + ECRH near qmin
TAEs
RSAEs
TAEs
RSAEs
#31567
#31569
AUG
FILD
ECE R~1.86m
ICRH + ECRH near qmin
RSAEs
#31569ECE R~1.81m
ECE R~1.86m
Outline
• Introduction and Motivation
• Impact of localized ECRH
on NBI Driven AEs
• Impact of localized ECRH
on ICRH Driven AEs
• Modeling of Experimental
Observations
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 19
First Modelling Attempts Focus on Stability
of NBI Driven AEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 20
AUGECRH Near qmin #31545
AUG
AUG
ECRH Near Axis #31541
AUG
RSAEs
BAAEs
ECE Spectrogram Near qmin
• Well modelled fast-ion distribution
• Based on TRANSP runs: linear
analysis
• Higher density in 31545 – higher
damping
• Very different ratio Te/Ti – all low-f
modes are weakly damped due to
reduced ion Landau damping
• Large Te/Ti – BAAEs in 31541
First Modelling Attempts Focus on Stability
of NBI Driven AEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 21
• Well modelled fast-ion distribution
• Based on TRANSP runs: linear
analysis
• Higher density in 31545 – higher
damping
• Very different ratio Te/Ti – all low-f
modes are weakly damped due to
reduced ion Landau damping
• Large Te/Ti – BAAEs in 31541
Different q-Profiles Lead to Significant
Changes in Spectra
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 22
• LIGKA calculates kinetic continuum with
and without fast-ions
• n=0 continua below TAE gap
• Small shear in #31545 changes spectra
significantly
• Wider modes expected in #31545
q
ρpol
#31545
#31541
TAEsRSAEs TAEs
RSAEs
LIGKA Predict Broader Eigenfunctions
w/o Fast-Ions in #31545
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 23
ES potential ES potential
LIGKA Calculates Kinetic Continuum Including
Fast-Ion Effects
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 24
#31545
• Maxwellian fast-ion
distribution with Teff = 25 keV
• Fast-ion pressure
comparable to total plasma
pressure
• FOW effects are not
considered
PEP
Pequi
Pel
PionTRANSP
ρpol
Fast-Ion Pressure Leads to n=0 Upshift
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 25
AUG
No EP FOW effects for continuum lead to an overestimation of EP
contribution to the pressure upshift but reasonable agreement with
experimental observation
• Simulations upshift to 150 kHz
/ Measured frequency 120 kHz
75 kHz
150 kHz
Fast-Ion Pressure Leads to n=0 Upshift
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 26
• Simulations upshift to 150 kHz
/ Measured frequency 120 kHz
75 kHz
150 kHz
No EP FOW effects for continuum lead to an overestimation of EP
contribution to the pressure upshift but reasonable agreement with
experimental observation
• Due to peaked EP profile, maximum
in continuum vanishes
• n=0 continuum reaches“background
particles only” – TAE gap
n=3 n=3, EP n=0 n=0, EP #31545
0.0 0.1 0.2 0.4 0.5 0.6 0.70.3ρpol
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 27
Modes Develop Continuum Interaction as
EP Density Increases
Ideal RSAEs transition to EPM as EP density increases in LIGKA
systematic scan
• Modes start to develop a continuum interaction that “moves”
radially outward
• Mode is damped by rather slow and cold part of the EP distribution
function (nEP being rather large)
20% TRANSP EP pressure
#31545 #31545 n=3n=3
100% TRANSP EP pressure
ρpolρpol
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 28
The Beta Suppression Mechanism* May Explain
Some Features of Measured Spectra
• ωAC has a mínimum when qmin = m/n, i.e. k‖=0
• As the temperature and density rise, the TAE
frequency drops and the GAM frequency
increases
• When beta is high enough so that
the range of the frequency sweep is zero*E. D. Fredrickson et al., Phys. Plasmas 14, 102510 (2007)
The coupling to GAM / BAEs may explain the absence of RSAEs
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 29
The Beta Suppression Mechanism* May Explain
Some Features of Measured Spectra
• ωAC has a mínimum when qmin = m/n, i.e. k‖=0
• As the temperature and density rise, the TAE
frequency drops and the GAM frequency
increases
• When beta is high enough so that
the range of the frequency sweep is zero*E. D. Fredrickson et al., Phys. Plasmas 14, 102510 (2007)
The coupling to GAM / BAEs may explain the absence of RSAEs
Conclusions / Outlook
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 30
• ECRH can have a major impact on AE stability
• First complete suppression of NBI driven RSAEs observed in AUG
• Impact on ICRH driven AEs still contradictory
• Discharges with suppressed RSAE activity show classical fast-ion profiles
• Standard AEs cause significant fast-ion losses as routinely observed
• Systematic scans still need to be done to isolate the effect of different
parameters changing with applied ECRH, e.g. q-profiles, Te/Ti, fast-ion
pressure, etc
• The beta suppression mechanism may explain some features of the
observed spectra
• Fast-ion effect must be taken into account in modelling to explain
observations
Back-up slides
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 16
AEs Cause Significant Coherent Fast-Ion Losses
Scintillator based Fast-Ion Loss Detector (FILD) measures
coherent losses induced by RSAEs and TAEs
• Both RSAEs and TAEs cause similar coherent losses
• Resonant losses found only for trapped particles
Resonance calculator
FILDFILD Spectrogram
#30370
M. Garcia-Munoz | 14th IAEA Technical Meeting on Energetic Particles | Vienna, Austria | 3rd September 2015 | Page 16
• Both RSAEs and TAEs cause similar coherent losses
• Resonant losses found only for trapped particles
FILD
AEs Cause Significant Coherent Fast-Ion Losses
Scintillator based Fast-Ion Loss Detector (FILD) measures
coherent losses induced by RSAEs and TAEs
The Primary Diagnostic Used for These
Experiments is the Fast-Ion Loss Detector (FILD*)
• FILD is a magnetic spectrometer
provides energy and pitch resolved measurements of escaping ions using collimator and tokamakmagnetic field
Local velocity-spacemeasurements like thesehelp to isolatefundamental mechanisms
*M. Garcia-Munoz et al., RSI. 80, 053503 (2009)
//vvvtot
fast ions
Plasma
ion
aperture
• FILD is a magnetic spectrometer
provides energy and pitch resolved measurements of escaping ions using collimator and tokamakmagnetic field
Local velocity-spacemeasurements like thesehelp to isolatefundamental mechanisms
Scintillator Image with Energy and Pitch
M. Garcia-Munoz et al., RSI. 80, 053503 (2009)
//vvvtot
fast ions
Plasma
ion
aperture
The Primary Diagnostic Used for These
Experiments is the Fast-Ion Loss Detector (FILD*)