PTRANSP Simulations of Toroidal Momentum Transport using GLF23 and Weiland Models

PTRANSP Simulations of Toroidal Momentum Transport

using GLF23 and Weiland Models

A. Kritz, F. D. Halpern, C. Wolfe, G. Bateman, A. Pankin

Department of Physics, Lehigh University, Bethlehem, PA

R. Budny, D. McCunePrinceton Plasma Physics Laboratory, Princeton, NJ

ITPA May 2007

ITPA Toroidal Momentum Transport May 8, 2007

Motivation• Momentum transport leads to

– Formation of rotation and velocity shear

– Formation of transport barriers (ITBs)

– Transition to H mode

– Suppression of resistive wall modes

• Momentum transport is less completely studied than anomalous thermal and particle transport

• Toroidal momentum transport model needed in description of the formation of internal and edge transport barriers

• Models for toroidal momentum transport are provided in the GLF23 and Weiland 19 transport models

– In many previous integrated simulations of tokamak discharges, these models were not employed

• A goal of this study is to test and to compare the predictions of these models with experimental data


Simulations of Toroidal Momentum Transport• Predictive PTRANSP simulations of turbulence driven

toroidal momentum transport carried out for 8 discharges

– NBI heated, H-mode JET discharges

• NUBEAM Monte Carlo code used to compute neutral beam injection heating profiles and torque sources

• Toroidal momentum, thermal transport computed using GLF23 or Weiland 19 models and neoclassical transport

– H-mode pedestal width and height computed - PEDESTAL module

– Edge toroidal rotation frequency is obtained from experiment

– Predictive particle transport to be installed in the PTRANSP code

• Sawtooth oscillations carried out using experimental times

– KDSAW module is used with complete magnetic reconnection

• Predicted H-mode toroidal velocity and temperature profiles in quasi-steady state discharges and data compared


New Weiland 19 Model Installed in PTRANSP• The Weiland 19 model is latest version of the extended drift wave

model (EDWM) developed at Chalmers University

• Model can be used to compute electron and ion thermal transport, particle transport, and momentum transport

• Physics improvements over previous versions of the model

– Momentum transport

– Improved finite beta effects

– Low and negative magnetic shear effects

– Varying correlation lengths

– Improved particle pinch effects

• Weiland 19 model implemented in the PTRANSP code

• Information about the model available in

– J. Weiland et al., P2.186, Proceedings of the 33rd EPS Conference 2006

• http://eps2006.frascati.enea.it/papers/pdf/P2_186.pdf

– J. Weiland, Collective Modes in Inhomogeneous Plasmas, IOP 2000


Discharge Parameters

0.2071.0161.1091.1561.2100.9110.5700.145ne0 (10-20 m-3)

2.515151414151212Paux (MW)

19.021.721.722.0022.0020.1416.6118.39Tdiagnostic (s)

31.1336.6152.0351.4844.5577.7867.4818.730 (Krad/s)

2.003.203.262.692.473.984.433.64Te0 (KeV)

2.063.014.324.033.205.435.113.19Ti0 (KeV)

2.02.72.72.72.72.72.62.6BTOR (T)

0.200.450.450.430.450.480.190.19

1.651.631.641.631.721.731.601.60

0.9840.890.9360.8910.8760.8700.8400.900a (m)

2.9523.0823.0703.0833.0903.0772.9042.894R (m)

6113252025520225201552014520093828738285Discharge

JETJETJETJETJETJETJETJETTokamak


Plasma Profiles for JET 52009

• High density, high power, high triangularity H-mode

– Plasma profiles shown at t=20 s

• Models differ in prediction of toroidal rotation frequency

– GLF23 over-predicts rotation frequency everywhere

– Weiland 19 model shows good agreement near the edge, but rotation too low at the core

• Rotation profiles are steeper near the edge and flat in core

– Most of the torque is deposited near the plasma edge


Plasma Profiles for JET 61132• Low density, low power, low

triangularity H-mode

– Plasma profiles shown at t=19 s

• Torque deposition concentrated near the axis

– Toroidal rotation profiles are peaked at the core

• GLF23 model over-predicts temperature profiles and toroidal rotation frequency

– Not enough transport, especially in the plasma core

• Weiland 19 model shows better agreement


Momentum Transport Diffusivity• Toroidal momentum transport

diffusivity shown as a function of minor radius

– Upper panel: JET 52009

– Lower panel: JET 61132

• Only diffusive terms utilized– Non-diagonal terms in Weiland 19

model not implemented in PTRANSP

• Momentum diffusivity is larger near the plasma edge

• GLF23 predicts lower toroidal momentum diffusivity than the Weiland 19 model predicts

– Especially in the plasma core

– Lower leads to higher rotation velocity for a given torque


Momentum Deposition Profiles• Simulated torque deposition profiles

shown as function of radius for two JET discharges

– Neutral beam injection accounts for most torque in the plasma core

– Charge exchange accounts for most torque in the plasma edge

• Torque density profiles depend on plasma density profiles

– JET52009 (high density): NBI torque is larger near plasma edge

– JET61132 (low density): NBI torque concentrated near plasma core

• Peaked torque density profiles result in peaked toroidal rotation profiles


Toroidal Rotation as Function of Time• Volume average of toroidal

rotation frequency shown as a function of time

– JET 52009 (high density)

• 7MW NBI at t = 15.0 sec +8MW NBI at t = 16.5 sec

– JET61132 (low density)

• 2.5MW NBI at t = 18.0 sec

• Weiland 19 usually results in better agreement for rotation average vs. time

– Especially after beams are on

• GLF23 model yields better agreement with experimental data in higher density discharges than in lower density discharges


Temperature and Rotation Profile Offset

• Profile offset computed using

• Average offset with GLF23 model:

– Te: 9 %

– Ti: 12 %

– : 17 %

• Average offset with Weiland 19 model:

– Te : 10 %

– Ti : 5 %

– : -9 %

N

=n

sim

X

XX

N=

1 maxexp,

exp1Offset G

LF

23

We

iland

1

9


Temperature and Rotation Profile Deviation

• RMS deviation computed using:

• Profile deviation with GLF23:

– Te : 18 %

– Ti : 19 %

– : 21 %

• Profile deviation with Weiland 19:

– Te : 15 %

– Ti : 14 %

– : 19 %

N

=n

sim

X

XX

N=σ

12

maxexp,

2exp 1 G

LF

23

We

iland

1

9


Total Energy and Toroidal Rotation Energy• Total stored energy is shown in upper

panel for 8 JET discharges

– 1st column: Experiment

– 2nd column: GLF23

– 3rd column: Weiland 19

• Total toroidal rotation energy is shown in lower panel for 8 JET discharges– Toroidal rotation energy a small

fraction of total stored energy

– Toroidal rotation in GLF23 simulations usually too fast near edge

• Weiland 19 model appears to yield better overall agreement with experimental data in these simulations


Summary• Weiland 19 model installed in PTRANSP

–Preliminary results show encouraging agreement with experiment

–Weiland 19 model will be submitted to PPPL TRANSP CVS repository

• Some numerical artifacts remain unresolved

• Predictive PTRANSP simulations of toroidal momentum and thermal transport were carried out for 8 JET discharges

–GLF23 and Weiland 19 models were used to compute the anomalous transport coefficients

–NTCC H-mode edge pedestal model used

• Toroidal rotation profiles and temperature profiles are predicted using GLF23 or Weiland 19 models

–Statistical measures of comparison with experimental data computed

–GLF23 model tends to over-predict rotation profiles

–Weiland 19 model tends to under-predict rotation profiles


Extra Slides


Flow Diagram for Self-Consistent Simulations

• Note: Simulations with Weiland 19 model without EB shear– Work is in progress!

Poloidal rotationfrequency (Exp.)

NBI torque

Turbulenttoroidal

momentumtransport

ExB ShearAnomalous

thermaltransport

Predictivetoroidalrotation

frequency

Temperatureprofiles

Powerdeposition

profiles

H-modepedestal

SawtoothCrashes

PEDESTAL module

KDSAW module PTRANSP core NUBEAM module

GLF23 or Weiland 19


Torque Sources as Function of Time

• Volume integral of simulated torque sources is shown as a function of time

– JET 52009 (high density): Upper panel

– JET 61132 (low density): Lower panel

– Curves smoothed

• In JET 61132, charge exchange at the edge is dominant torque source

– Significant even before NBI turned on

• In JET 52009, dominant source is JB torque

– Spread out across plasma radius

• Total torque input ratio 52009/61132 consistent with power input ratio

Total injected

CX

Beam to ions

Thermalization

JxB

Total injected

CX

Beam to ions

Thermalization

JxB

JET 52009

JET 61132

To

rqu

e [

N m

]T

orq

ue

[N

m]

Documents

PTRANSP Simulations of Toroidal Momentum Transport using GLF23 and Weiland Models