Speaker
Iulian Gabriel Miron
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1062.pdf
Modelling the NTM evolution directly from JET experimental data
I.G. Miron1 , S. Nowak2 and JET Contributors∗
1 National Institute for Lasers, Plasma and Radiation Physics, Magurele-Bucharest, Romania
2 Istituto di Fisica del Plasma, CNR, Milano, Italy
∗ See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001"
A quasi-analytic model [1] and appropriate code are built in order to calculate the evolution
of the NTM delta prime stability index and subsequent island width. The former is an explic-
itly time dependent derived quantity whereas the latter satisfies a modified Rutherford equation
having the previously derived analytic delta prime term and a heuristic quantity for the boot-
strap term. To obtain explicitly dynamic quantities, the following strategy is used: the involved
perturbed equations are Laplace transformed in order to get rid of intrinsic time derivatives. The
Laplace transformed perturbed equations are solved and the solutions are arranged via partial
fraction decomposition method in order to be easily inverse Laplace transformed, the latter pro-
cedure being the final step to be achieved.
JET hybrid discharge experimental data are used to test the model accuracy regarding the evo-
lution of a 3/2 NTM triggered by a sawtooth. No triggering sawtooth is considered in our ap-
proach, which would pointlessly complicate the model. Instead, a resonant external perturbation
is considered to replace the sawtooth as a trigger for the NTM. Despite the fact that the theoret-
ical model is built in order to describe the behavior of the small perturbations from the equilib-
rium state, therefore seeking for constant equilibrium quantities in order to be valid, the model
uses stepwise varying JET data tables for the latter quantities and seems to simply work. The
equilibrium quantities time growth rates are smooth enough in order to not break the perturbed
model validity and to not significantly affect the NTM evolution during the period of interest.
The NTM amplitude and frequency behavior are finally shown along with its corresponding
magnetic island evolution.
References
[1] I.G. Miron, P2.060, 43rd EPS Conference on Plasma Physics, 4-8 July 2016, Leuven, Belgium.
