LIGKA: a new gyrokinetic code in realistic tokamak geometry with full orbits
description
Transcript of LIGKA: a new gyrokinetic code in realistic tokamak geometry with full orbits
LIGKA: a new gyrokinetic code in realistic tokamak geometry with full orbits
S. Günter, P. Lauber, A. Könies, S. PinchesMax-Planck-Institut für Plasmaphysik, Garching/Greifswald, Germany
D. Testa, A. FasoliCRPP Lausanne, Switzerland
and comparison with experiment
• LIGKA
– Linear gyrokinetic non-perturbative tokamak model– [Ph. Lauber, Ph.D. Thesis, T.U. München 2003]
• CAS3D-K
– Linear perturbative drift-kinetic approach for
stellarators– [A. Könies, Phys. Plasmas 7 1139 (2000)]
• HAGIS
– Initial value nonlinear drift-kinetic f model– [S. D. Pinches et al., Comput. Phys. Commun. 111, 131 (1998)]
Codes developed at IPP
• Linear shear Alfven perturbations– Calculates mode frequency, growth rate and mode
structure, including FLR effects
• Non-perturbative– Allows change from MHD eigenmode structure– Nonlinear eigenvalue problem (Nyquist solver)
H. Qin, W. M. Tang, G. Rewoldt, Phys. Plas. 6 2544 (1999)Based on model by
LIGKA: Linear GyroKinetic shear Alfven physics
In addition:
• Accurate treatment of unperturbed particle orbits– Numerical integration of full
drift orbit effects (HAGIS)
• General tokamak geometry– From numerical equilibrium
code (e.g. HELENA)
H. Qin, W. M. Tang, G. Rewoldt, Phys. Plas. 6 2544 (1999)Based on model by
LIGKA: Linear GyroKinetic shear Alfven physics
LIGKA: Linear GyroKinetic shear Alfven physics
qR
vA2
JET #42979, t = 10.121s
LIGKA
CASTOR
Benchmark for TAE mode with open gap: global mode, ballooning structure
[D. Borba and W. Kerner, J. Comp. Phys. 153 101 (1999)]
• Global modes• Anti-ballooning character• Formed at top of TAE gap• Stronger damping than TAE
1 ik 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Radius
Ele
ctro
stati
c Pote
nti
al,
p=0
p=1
p=2
p=3
Frequency
[
/A]
Radius0.66 0.84
0.45
0.75
JET #42979, t = 10.121s
Shear Alfvén
Continuum
p=0
p=1
p=2
p=3
Incr
easi
ngly
dam
ped
LIGKA: Benchmark for KTAE modes
• Modeled via change in LIGKA code boundary conditions– No vacuum region
• Systematically find all stable modes– Including damping rates
• Analogous to TAE antenna experiments
– [Fasoli et al., PRL 76 1067 (1996)]
Frequency [/A]
Pla
sma r
esp
onse
JET #42979, t = 10.121sTAE
KTAE
p=0p=1
p=2
p=3p=4
10
12
14
16
18
20
0.35 0.4 0.45 0.5 0.55 0.6
[Conner et al, Proc. 21st EPS Conf., Montpellier, 18B 616 (1996)]
LIGKA: External antenna drive
Comparison with JET damping rate experiments
• so far: often large discrepancies between measured and calculated damping rates for TAE modes (except for PENN model)
• Wrong isotope scaling for fluid model reported
Fasoli, Jaun
ii
iiieff nmnA /
CAS3D-K (passing particles only)
Asymptotic expansion in Aeff
Local approximation for passing particles
LIGKA (passing particles only)
0.5 1 1.5 2 2.5 3 3.5Aeff ~ mi/mp
0
0.1
0.2
0.3
0.4A. Könies
[%
]
JET #42979, t = 10.121s
Isotope mass scaling ok in hybrid code
• Local fluid approximation: Aeff-1/2
• Kinetic model agrees with hybrid model: LIGKA and CAS3D-K
Comparison with JET experiments
PENN: - significant radiative damping in the plasma centre
- mode structure not TAE-like
Testa (2004): experimental mode structure (JET, similar discharge)
Comparison with PENN results
open TAE gap for experimental density profile
TAE gap closes for modified density profile (within exp. error bars!)
vA= B/ 0experimental density profilemodified density profile
Comparison with PENN results
Kinetic effects important if TAE gap closed
Damping rates increase up to 0.6 % (experiment ~2 %, open gap ~0.25 %)
# 52206, t=62.9s
ω/ωA0
ωTAE
=0.340
10 normalised radius
1
2e19
normalised radius0
0.70.8
temperature: ion / electron [keV]
2e19
q - profile
density / experimental density profile
1
4
2
3
0 1normalised radius0
Comparison with JET experiments
Z
R
ω/ωTAE = 0.98, γ/ω = 0.92%
3 4Radius [m]
arbi
trar
y un
its
total perturbation(outward midplane)
0
0 1normalised radius
m=1m=2
m=30
Comparison with JET experiments
ω/ωTAE = 0.98, γ/ω = 0.92%
3 3.2 3.4 3.6 3.8 4
Radius [m]
arbi
trar
y un
its
total perturbation(outward midplane)
0
Comparison with JET experiments
γ/ω = 1.5%
Summary and Conclusion
LIGKA: - linear gyrokinetic code with realistic tokamak geometry and fast particle orbits
• Agreement between calculated and measured damping rates strongly depends on density profile at the plasma edge (TAE gap open or closed)
• Is there a difference between (limiter) discharges with qa being a rational value and not?
Outlook:
• Code can deal with energetic particle modes as well (non-perturbative)
• Coupling to non-linear HAGIS code
• Further comparison with experiments
• ITER predictions