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Experimental turbulence studies for gyro-kinetic code validation using advanced microwave diagnostics Ulrich Stroth, A. Bann Navarro, A. Biancalani, E. Blanco, C. Bottereau, F. Clairet, S. Coda, G.D. Conway, T. Eibert, T. Estrada, A. Fasoli, L.

SLIDE 1

Presented at the FEC, St. Petersburg 18.10.2014

Experimental turbulence studies for gyro-kinetic code validation using advanced microwave diagnostics

Ulrich Stroth, A. Banón Navarro, A. Biancalani, E. Blanco, C. Bottereau, F. Clairet,

S. Coda, G.D. Conway, T. Eibert, T. Estrada, A. Fasoli, L. Guimarais, T. Görler, Ö. Gürcan, T. Happel, P. Hennequin, Z. Huan, F.

Jenko, W. Kasparek, C. Koenen, A. Krämer-Flecken, C. Lechte, M.E. Manso, P. Manz, A. Medvedeva, D. Molina, V. Nikolaeva,

L. Porte,
D. Prisiazhniuk, T. Ribeiro, B.D. Scott, U. Siart, P. Simon, A, Storelli, L. Vermare, S. Wolf,

and the ASDEX Upgrade team

SLIDE 2

Gyro-kinetic and gyro-fluid codes provide a realistic simulation of turbulence in tokamaks

Codes reproduce experimental power and particle fluxes Codes make detailed predictions on the microscopic structure of turbulence

− fluctuations in all parameters, cross-phase and phase velocities − spatial distribution of the fluctuations − interactions of zonal flows and GAMs with the turbulence

Experimentally test the physical models used in the codes on a microscopic basis

U. Stroth, FEC, St. Petersburg 18.10.2014

Potential fluctuations from GENE simulations

Jenko, POP 2000

SLIDE 3

Microwave diagnostics for turbulence studies on AUG

U. Stroth, FEC, St. Petersburg 18.10.2014

FZJ 5 antenna correlation refl. Structure and propagation of fluctuations IST Multi-band relf. HFS/LFS asymmetries CEA Ultra-fast swept refl. Radial structure of fluctuations Turbulence spreading MIT correlation ECE Temperature fluctuations n-Te cross-phases IPP 2 channel Doppler refl. Scale resolved fluctuations and propagation velocity IPP+LPP 2 channel Doppler refl. Scale resolved fluctuations and propagation velocity

SLIDE 4

Presented at the FEC, St. Petersburg 18.10.2014

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

SLIDE 5

Example: Analysis of density fluctuation spectra at the plasma edge (AUG) Slope is similar (-4) but “knee” appears at different wavenumbers Full-wave simulations indicate non-linear saturation at large amplitudes shifting knee to larger wavenumbers Comparison of wavenumber spectra from experiment and simulation has to be done through a synthetic diagnostic

Experiment-theory comparison needs synthetic diagnostics

. (Tröster, PhD 2008) Lechte, Görler et al, PPCF t.b. subm.

SLIDE 6

Presented at the FEC, St. Petersburg 18.10.2014

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

SLIDE 7

ECRH drives plasma from ITG towards the TEM regime Core density peaking (and change in rotation) is successfully described by gyro-kinetic calculations (GS2) Collisionality  turbulence regime  density peaking  plasma rotation Test the models used in the codes on the basis of fluctuations

McDermott PPCF 2011

ECRH ECRH

Core turbulence in the ITG-TEM regime

Angioni PPCF 2009, Fable PPCF 2010, McDermott PPCF 2011, Angioni PRL 2012, McDermott NF 2014

U. Stroth, FEC, St. Petersburg 18.10.2014

SLIDE 8

H-mode (2.5 MW, NBI) add up to 1.8 MW

ff-axis ECRH

LTe = Te/Te successfully modified

Create discharges in the domain of the ITG-TEM transition

Profiles respond as expected

− Density more peaked, rotation flattens

U. Stroth, FEC, St. Petersburg 18.10.2014

8 ECRH ECRH

Happel, PoP submitted

SLIDE 9

Stability analysis from linear GENE simulations

TEM and ITG growth rates Both phases are in the ITG regime ECRH pushes plasma towards the TEM regime What can we expect from the ITG-TEM transition?

− About the same turbulent scales − Shift of phase velocity from the ion- to the electron- diamagnetic drift direction

U. Stroth, FEC, St. Petersburg 18.10.2014

Happel, PoP submitted

SLIDE 10

Scale resolved observations from Doppler reflectometry

Large scale amplitudes increase Phase velocity of about 3 km/s into electron- diamagnetic direction (larger than expected)

U. Stroth, FEC, St. Petersburg 18.10.2014

Happel, PoP submitted

krs  1

SLIDE 11

Electron and ion power fluxes matched within experimental error bars Radial increase in fluctuation amplitude reproduced quantitatively Dependence on heating power not yet recovered

Comparison with GENE simulations

U. Stroth, FEC, St. Petersburg 18.10.2014

Happel, PoP submitted

SLIDE 12

At lower collisionality a transition from ITG to TEM can be expected Strongest velocity shift into electron-diam. direction is also at krs  0.75 Velocity change consistent with GENE predictions but experimental velocities are again larger (km/s) than in simulations (100 m/s)

Change of turbulence through collisionality in Tore Supra

U. Stroth, FEC, St. Petersburg 18.10.2014

Vermarre PoP 2011 Electron diamagnetic direction

SLIDE 13

Presented at the FEC, St. Petersburg 18.10.2014

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

SLIDE 14

Frequency scaling of Geodesic Acoustic Modes

Systematic configuration scan on AUG Empirical model by Conway reproduces average trend Model by Gao reproduces configuration dependence, frequency is too low

U. Stroth, FEC, St. Petersburg 18.10.2014

Elongation k Divertor Limiter

Simon, PhD. Gao PST 2011 Conway PPCF 2008

SLIDE 15

Spatiotemporal structure of GAMs in AUG

U. Stroth, FEC, St. Petersburg 18.10.2014

P. Simon, PhD

Correlation Doppler reflectometry Gyro-fluid simulations (GEMR)

Frequency “locking” over wider radial region in exp. and simulation No clear sign of radial propagation

SLIDE 16

Doppler reflectometry Frequency plateaus are also seen but general trend of cs/R is recovered

Structure GAM in Tore Supra

U. Stroth, FEC, St. Petersburg 18.10.2014

A. Storelli, PhD, TTG 2014

frequency (kHz)

r

SLIDE 17

GAM damping in AUG and Tore Supra

Larger GAM amplitudes in circular plasmas (AUG) Larger GAM amplitudes at lower collisionality (Tore Supra)

U. Stroth, FEC, St. Petersburg 18.10.2014

P. Simon, PhD
A. Storelli, PhD, TTG 2014

GAM amplitude follows qualitatively the inverse damping rate

SLIDE 18

Presented at the FEC, St. Petersburg 18.10.2014

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

SLIDE 19

Strong HFS/LFS asymmetry (ballooning); increasing with frequency Stronger asymmetry in the SOL at low frequencies; DN and SN are similar Comparison with gyro-fluid simulations (GEMR) under way

Poloidal structure of turbulence HFS/LFS reflect. on AUG

U. Stroth, FEC, St. Petersburg 18.10.2014

V. Nikolaeva, PhD

HFS LFS HFS LFS

SLIDE 20

Presented at the FEC, St. Petersburg 18.10.2014

Outline

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

SLIDE 21

Search for non-local effects and fast turbulence spreading

In ECRH modulation experiments on LHD, fluctuations reacted faster than local plasma parameters Reaction of edge Doppler data to core ECRH modulation on AUG

Conditional averaging on wavelet filtered fluctuation signals

Density profiles from ultra-fast swept reflectometer during ECRH switch-on So far no evidence for non-local transport in the density Extent search to lower collisionality

U. Stroth, FEC, St. Petersburg 18.10.2014

Inagaki NF 53 (2013)

ECRH switch 4000 profiles in 10 ms

AUG #31364

A. Medvedeva, PhD

SLIDE 22

To be installed and tested on AUG and TCV

Advanced antenna developments for nuclear devices

U. Stroth, FEC, St. Petersburg 18.10.2014

32 horn array antenna Passive phase shifter

S. Wolf, PhD

Active phase shifter

C. Koenen, PhD

SLIDE 23

Presented at the FEC, St. Petersburg 18.10.2014

Summary

Validation of physical models in turbulence codes needs to be done on a microscopic level in a comprehensive fashion This is not an easy task: it requires excellent hardware and often synthetic diagnostics and many CPU hours First results encouraging: agreement is found e.g. for

̶ Wavenumber spectra, radial variation of fluctuation amplitudes; change in drift direction at ITG- TEM transition ̶ GAM frequency scaling, damping and frequency plateaus

Experimental turbulence studies for gyro-kinetic code validation using advanced microwave diagnostics

Ulrich Stroth, A. Banón Navarro, A. Biancalani, E. Blanco, C. Bottereau, F. Clairet,

Jenko, W. Kasparek, C. Koenen, A. Krämer-Flecken, C. Lechte, M.E. Manso, P. Manz, A. Medvedeva, D. Molina, V. Nikolaeva,

and the ASDEX Upgrade team

Gyro-kinetic and gyro-fluid codes provide a realistic simulation of turbulence in tokamaks

Codes reproduce experimental power and particle fluxes Codes make detailed predictions on the microscopic structure of turbulence

− fluctuations in all parameters, cross-phase and phase velocities − spatial distribution of the fluctuations − interactions of zonal flows and GAMs with the turbulence

Experimentally test the physical models used in the codes on a microscopic basis

Potential fluctuations from GENE simulations

Jenko, POP 2000

Microwave diagnostics for turbulence studies on AUG

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

Experiment-theory comparison needs synthetic diagnostics

. (Tröster, PhD 2008) Lechte, Görler et al, PPCF t.b. subm.

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

ECRH drives plasma from ITG towards the TEM regime Core density peaking (and change in rotation) is successfully described by gyro-kinetic calculations (GS2) Collisionality  turbulence regime  density peaking  plasma rotation Test the models used in the codes on the basis of fluctuations

McDermott PPCF 2011

Core turbulence in the ITG-TEM regime

Angioni PPCF 2009, Fable PPCF 2010, McDermott PPCF 2011, Angioni PRL 2012, McDermott NF 2014

H-mode (2.5 MW, NBI) add up to 1.8 MW

LTe = Te/Te successfully modified

Create discharges in the domain of the ITG-TEM transition

Profiles respond as expected

− Density more peaked, rotation flattens

Happel, PoP submitted

Stability analysis from linear GENE simulations

TEM and ITG growth rates Both phases are in the ITG regime ECRH pushes plasma towards the TEM regime What can we expect from the ITG-TEM transition?

− About the same turbulent scales − Shift of phase velocity from the ion- to the electron- diamagnetic drift direction

Happel, PoP submitted

Scale resolved observations from Doppler reflectometry

Large scale amplitudes increase Phase velocity of about 3 km/s into electron- diamagnetic direction (larger than expected)

Happel, PoP submitted

krs  1

Electron and ion power fluxes matched within experimental error bars Radial increase in fluctuation amplitude reproduced quantitatively Dependence on heating power not yet recovered

Comparison with GENE simulations

Happel, PoP submitted

At lower collisionality a transition from ITG to TEM can be expected Strongest velocity shift into electron-diam. direction is also at krs  0.75 Velocity change consistent with GENE predictions but experimental velocities are again larger (km/s) than in simulations (100 m/s)

Change of turbulence through collisionality in Tore Supra

Vermarre PoP 2011 Electron diamagnetic direction

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

Frequency scaling of Geodesic Acoustic Modes

Systematic configuration scan on AUG Empirical model by Conway reproduces average trend Model by Gao reproduces configuration dependence, frequency is too low

Elongation k Divertor Limiter

Simon, PhD. Gao PST 2011 Conway PPCF 2008

Spatiotemporal structure of GAMs in AUG

Correlation Doppler reflectometry Gyro-fluid simulations (GEMR)

Frequency “locking” over wider radial region in exp. and simulation No clear sign of radial propagation

Doppler reflectometry Frequency plateaus are also seen but general trend of cs/R is recovered

Structure GAM in Tore Supra

frequency (kHz)

r

GAM damping in AUG and Tore Supra

Larger GAM amplitudes in circular plasmas (AUG) Larger GAM amplitudes at lower collisionality (Tore Supra)

GAM amplitude follows qualitatively the inverse damping rate

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Outline

Strong HFS/LFS asymmetry (ballooning); increasing with frequency Stronger asymmetry in the SOL at low frequencies; DN and SN are similar Comparison with gyro-fluid simulations (GEMR) under way

Poloidal structure of turbulence HFS/LFS reflect. on AUG

HFS LFS HFS LFS

Outline

Importance of synthetic diagnostics Transition from ITG to TEM turbulence in the plasma core Geodesic Acoustic Modes Poloidal asymmetry of turbulent fluctuations Non-local effects in turbulence

Search for non-local effects and fast turbulence spreading

In ECRH modulation experiments on LHD, fluctuations reacted faster than local plasma parameters Reaction of edge Doppler data to core ECRH modulation on AUG

Conditional averaging on wavelet filtered fluctuation signals

Density profiles from ultra-fast swept reflectometer during ECRH switch-on So far no evidence for non-local transport in the density Extent search to lower collisionality

Inagaki NF 53 (2013)

To be installed and tested on AUG and TCV

Advanced antenna developments for nuclear devices

32 horn array antenna Passive phase shifter

Active phase shifter

Summary

Validation of physical models in turbulence codes needs to be done on a microscopic level in a comprehensive fashion This is not an easy task: it requires excellent hardware and often synthetic diagnostics and many CPU hours First results encouraging: agreement is found e.g. for

̶ Wavenumber spectra, radial variation of fluctuation amplitudes; change in drift direction at ITG- TEM transition ̶ GAM frequency scaling, damping and frequency plateaus

…but there is still much to do, e.g.

̶ Wavenumber spectra ̶ The correct turbulent phase velocity ̶ ZF and GAM interaction with turbulence ̶ …