predictive modelling of plasma rotation (examples from itpa itb database)

Transport/ITB IPTA Meeting, St Petersburg, 8-12 April 2003

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Predictive Modelling of Plasma Rotation (examples from ITPA ITB database)

V.V. Parail1T. Tala2, A. Becoulet3, G. Corrigan1,X. Garbet3, D. Heading1, X. Litaudon3, P.I. Strand4 and J. Weiland4

1UKAEA Fusion Association, Culham, UK; 2Association Euratom-Tekes, Finland; 3Association Euratom-CEA, Cadarache, France; 4Chalmers University,

Gothenburg, Sweden

• Selection of shots;• Transport models used in simulation• Comparative role of plasma rotation and negative/zero magnetic shear in ITB formation;• Conclusions and future plans


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Selection of shots Three pairs of plasmas with ITB from JET, JT-60U

and DIII-D (each pair has one shot with and one without negative shear) were used to simulate plasma rotation;

Discharges from JET and DIII-D have tangential NBI injection, which provides adequate torque to generate strong toroidal rotation;

JT-60U uses quasi-perpendicular injection so that toroidal rotation is controlled mainly by neo-classical effects;

Actually JT-60U shots give very good complimentary information about plasma rotation.


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Transport models (1)

• JETTO model (Bohm/gyroBohm)

alneogyroeITG

BEBohmee Cs

,1, 1.0

ie

ieD

neoigyroi

ITG

BE1Bohmii Cs10

,, .

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Transport models (2)

• Hahm-Burrell formulation of the shearing rate was used in simulations:

RB1

BvBvenTn

BRB

i

ii2

BE)(


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Transport models (3)• Full implementation of Weiland model with off-diagonal elements was used as a second transport model;• Both JETTO and Weiland models were complemented by the full matrix of the neo-classical transport coefficients from

NCLASS;• Weiland model uses the same Hahm-Burrell formulation of the shearing rate;• Same assumption was used for anomalous viscosity:

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Results of the modelling (JET)


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Legend:

- - - Experiment

__ JETTO, C3=0.9

__ JETTO, C3=1.2;

__ Weiland, normal;

__ “-” Vtorx5;

__ “-” ExBx3


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Legend:

- - - Experiment

__ JETTO, C3=0.5

__ JETTO, C3=1.5;

__ Weiland, normal;

__ “-” Vtorx5;

__ “-” ExBx5


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Results of the modelling (JT-60U)


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Legend:

- - - Experiment

__ JETTO, C3=1.2

__ Weiland, normal;

__ “-” Vtorx3;

__ “-” ExBx10


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Legend:

- - - Experiment

__ JETTO, C3=0.5

__ JETTO, C3=1.2;

__ Weiland, normal;

__ “-” Vtor;

__ “-” ExBx10


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Results of the modelling (DIII-D)


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Legend:

- - - Experiment

__ JETTO, C3=0.5

__ JETTO, C3=1.0;

__ Weiland, normal;

__ “-” ExBx5


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Conclusions (1)

Bohm/GyroBohm model reproduces ITBs quite reasonably;

Toroidal rotation is reproduced with

Plasma rotation (both toroidal and poloidal) seems to play a role in ITB formation particularly in discharges without negative magnetic shear;

Bohm/gyroBohm modes tends to over-estimate ITB width in discharges with negative magnetic shear;

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Conclusions (2)

Weiland model reproduces ITBs only if much increased shearing rate (by 3-10 times);

Generally Weiland model reproduces “weak” barrier much better than the “strong” one;

Same conclusion applies with respect to plasma rotation: it is very difficult to reproduce strong barrier;

Although predictive modelling of plasma rotation does add a “degree of freedom” into simulation, generally it affect the result in a predictable way;

predictive modelling of plasma rotation (examples from itpa itb database)

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