29th Symposium on Fusion Technology (SOFT 2016)

P1.044 A 3D Electromagnetic Model of the Iron Core in JET

5 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 44

Poster C. Plasma Engineering and Control P1 Poster session

Speaker

Francesco Pizzo (Department of Industrial and Information Engineering)

Description

The Magnet and Power Supplies system in JET includes a ferromagnetic core able to increase the transformer effect by improving the magnetic coupling with the plasma. The iron configuration is based on an inner cylindrical core and eight returning limbs; the ferromagnetic circuit is designed in such a way that the inner column saturates during standard operations [1]. The modelling of the magnetic circuit is a critical issue because of its impact on several applications, including equilibrium and reconstruction analysis required for control applications. The most used model in present applications is based on Equivalent Currents (ECs) placed on the iron boundary together with additional specific constraints, in 2D axisymmetric frame. The (circular) ECs are chosen, by using the available magnetic measurements, to best represent the magnetic polarization effect [1]. Due to the axisymmetric assumption such approach is not well suited to deal with significant 3D effects, e.g. arising in operations with Error Field Correction Coils (EFCC). In this paper a new methodology is proposed, based on a set of 3D-shaped ECs and able to better model the actual 3D magnetization. According to a well assessed approach [2], the 3D shape of ECs is represented by a set of small filamentary sources. The methodology has been successfully validated in a number of JET experiments where 3D effects are generated by EFCC currents. The new procedure has been designed to be easily coupled with equilibrium or reconstruction codes such as EFIT/V3FIT. [1] O'Brien D. P., et al. "Equilibrium analysis of iron core tokamaks using a full domain method." Nuclear fusion 32.8 (1992):1351. [2] Chiariello A. G., et al. "Effectiveness in 3-D Magnetic Field Evaluation of Complex Magnets." IEEE Trans.Magn., vol.51.3, 2015.