Speaker
Francesco Carpanese
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1050.pdf
Kinetic equilibrium reconstruction on TCV:
towards a self-consistent approach
F. Carpanese1 , O.Sauter1 , A. Merle1 , J-M.Moret and the TCV team
1 EPFL-SPC, Switzerland
The equilibrium reconstruction of TCV plasmas is usually performed making use of only
external magnetic measurements. Not using internal measurements from the confined
plasma, such as those provided by an MSE diagnostic, results in an ambiguous
reconstruction of the current and pressure profiles, which ultimately reflects on the q
profile. Moreover, the limited number of basis functions used to represent the plasma
profiles when computing the equilibrium makes the latter inaccurate particularly in the
presence of steep pressure gradients or a peaked current density profile.
When kinetic plasma measurements (ne, Te, Ti) are used in the reconstruction one refers to
kinetic equilibrium reconstruction: the pressure is constrained by measurements while the
current density profile is constrained by solving the time-dependent flux surface averaged
Ohm’s law. We tackled this problem by coupling the free-boundary equilibrium
reconstruction code LIUQE [1] to the transport code ASTRA [2] solving just for the flux
surface averaged Ohm’s law. The coupling is performed by taking the pressure and current
density profiles from ASTRA as basis functions for LIUQE but allowing them to be scaled
in order to minimize the error between the equilibrium solution and magnetic
measurements. This scheme was chosen with the purpose of re-using existing, well
benchmarked tools as much as possible with the smallest possible number of modification
so that their future individual upgrades will not affect the coupling. The scheme has proven
to converge and to produce more realistic evolution of internal inductance in the presence
of central and off-axis current drive.
It will also be used to study H- mode plasmas in the presence of NBI heating and the effects
of strong pressure flattening due to NTMs. The tool can be run autonomously (without
human interaction) and is aimed at being used routinely for experimental data analysis of
TCV discharges.
[1] Pereverzev, G. V., & Yushmanov, P. N. (2002). ASTRA. Automated System for
TRansport Analysis in a tokamak.
[2] Moret, J. M., Duval, B. P., Le, H. B., Coda, S., Felici, F., & Reimerdes, H. (2015).
Tokamak equilibrium reconstruction code LIUQE and its real time implementation. Fusion
Engineering and Design, 91, 1-15.
