Speaker
Kian Rahbarnia
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1041.pdf
Improvements of magnetic diagnostic systems and bootstrap current
characterization at the stellarator Wendelstein 7-X
K. Rahbarnia1, T. Andreeva1, U. Neuner1, H. Thomsen1, J. Schilling1, J. Svensson1, N. Lauf1,
J. Geiger1, Y. Turkin1, T. Bluhm1, M. Zilker1, B.B. Carvalho2, D. Hathiramani1, M. Endler1
and the Wendelstein 7-X Team
1
Max Planck Institute for Plasma Physics, 17491 Greifswald, Germany
2
Instituto de Plasmas e Fusao Nuclear Instituto Superior Tecnico, Lisbon, Portugal
The second operational phase (OP1.2a) at the stellarator Wendelstein 7-X (W7-
X) took place from August to December 2017. Significant improvements of the
magnetic diagnostic system have been implemented compared to the previous
operational phase. About 90% of the installed sensors were put into operation,
which include 2 diamagnetic loops, 6 Rogowski coil arrangements, 36 saddle
coils and 125 Mirnov coils, distributed in all 5 modules of W7-X. Measured raw
data is directly streamed into the W7-X archive. After each plasma pulse
automatized data analyzing software calculates magnetic fluxes of all sensors, as
well as the compensated diamagnetic energy and plasma current. Based on this
data source, implemented in the MINERVA framework, the reconstruction of
magnetic equilibria has been developed using the Variational Moments
Equilibrium Code VMEC.
Plasma pulses with a duration of up to 20s in combination with plasma density
feedback allowed the application of the magnetic diagnostics for studies of the
bootstrap current which are complemented by theoretical predictions. In these
studies the minimization of bootstrap currents in certain magnetic field
configurations could be confirmed.
Additionally, a plasma heating interlock signal, which is generated from the
measurement signal of the diamagnetic energy has been tested and prepared for
the upcoming operational phases.
