Speaker
Rainer Fischer
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1042.pdf
Fast and reliable reconstruction of the current distribution
at ASDEX Upgrade
R. Fischer1 , A. Bock1 , A. Burckhart1 , S.S. Denk1 , M. Dunne1 , O. Ford1 , L. Giannone1 ,
A. Gude1 , M. Maraschek1 , R.M. McDermott1 , A. Mlynek1 , E. Poli1 , M. Rampp2 ,
D. Rittich1 , M. Weiland1 , M. Willensdorfer1 , and the ASDEX Upgrade Team
1 Max-Planck-Institutfür Plasmaphysik, Boltzmannstr. 2, D-85748 Garching, Germany
2 Max Planck Computing and Data Facility, Giessenbachstr. 2, D-85748 Garching, Germany
Fast and reliable reconstruction of the current distribution is of particular interest for exper-
imental on-the-fly plasma scenario development. This is of major importance for the develop-
ment of advanced scenarios where fine-tuning of the q-profile using heating and current-drive
actuators is desired. The goal is to reconstruct the most reliable equilibrium achievable from
all available experimental data and modelling constraints before the setting of the next plasma
discharge has to be decided. The number of plasma discharges for the typically challenging per-
formance optimization is often large but required to be as small as possible for budget reasons.
At ASDEX Upgrade the goal is to have the most reliable current and q-profiles within 20 min
to be available for plasma parameter optimization before the next discharge.
The first 10 min after the previous discharge are foreseen for kinetic profile reconstruction
employing an integrated data analysis (IDA) approach of all profile diagnostics available shortly
after the previous plasma discharge (not necessarily in real-time). The second 10 min are ded-
icated for equilibrium reconstruction with a temporal resolution of 5 ms for a typical plasma
discharge of 8 s. The equilibrium reconstruction is based on the coupling of a Grad-Shafranov
(GS) solver with the integration of the current diffusion (CD) equation employing a physical
coupling of neighboring time points. The ingredients are reliable electron and ion temperature
and density profiles from the IDA approach, fast-ion pressure and driven current profiles from
the recently developed RABBIT code, the electron-cyclotron driven current from the recently
upgraded TORBEAM code, an improved bootstrap-current evaluation, all magnetic data of an
extended set of poloidal-field and diamagnetic-loop measurements, internal current measure-
ments from (imaging)MSE and polarimetry, and an automized sawtooth detection algorithm.
The fast and reliable current reconstruction is achieved with the equilibrium code IDE paral-
lelized using an OpenMP scheme within the Grad-Shafranov solver, within the RABBIT code
of up to 8 NI-beams and within the TORBEAM code. On top of this, an MPI (Message Passing
Interface)-based approach is applied for parallel calculations of the GS-solver response ma-
trix and for parallel TORBEAM evaluations of up to 8 EC-beams for the CD-integration. This
enables parallel calculations on up to approx. 40 CPU cores of a server-class machine.
