Speaker
Paolo Bettini
(Consorzio RFX)
Description
RFX-mod is equipped with an advanced active control system of MHD instabilities, which consists of 48x4 saddle coils, housed inside a stainless steel Toroidal Support Structure, and 48x4 radial field sensor loops processed in real time to drive the currents in the control coils. Thanks to the high flexibility of this system [1], RFX-mod operations in the last years have allowed to reach the design plasma current of 2 MA in the RFP configuration and to investigate the very low q Tokamak regimes.
In order to further extend the operational space of RFX-mod, a major upgrade of its magnetic front-end is now being studied. By removing the Inconel vacuum vessel, presently surrounding the plasma, the thin (3 mm) stabilizing copper shell will become the conductive surface closest to the plasma, thus decreasing the shell proximity and reducing the deformation of the Last Closed Magnetic Surface.
The aim of this paper is the accurate calculation of the 3D magnetic field structure produced by the MHD active coils in RFX-mod Upgrade, in the presence of the new complex (geometrically an topologically) conducting structures surrounding the plasma, with particular emphasis on the evaluation of the toroidal coupling effects and the aliasing affecting the measured magnetic field harmonics.
A 3D model has been developed, which includes the finest geometrical details of the conductive structures and two sets of non-axisymmetric field sources (48x4 saddle coils for MHD instabilities control and 2x11 saddle coils for local (poloidal gaps) error field control). A state of the art integral formulation [2] [3] is used to solve the eddy current problem in the frequency domain.
[1] P. Zanca, et al., 2012 PPCF 54 (12) 124018–124027
[2] P. Bettini et al., 2015 IEEE TMAG 51 (3) 7203904
[3] P. Alotto et al., 2015 IEEE TMAG 10.1109/TMAG.2015.2488699
Co-authors
Giuseppe Marchiori
(Consorzio RFX, Padova, Italy)
Leonardo Pigatto
(Centro Ricerche Fusione (CRF), Università di Padova, Via Gradenigo, 6/A, Italy)
Lionello Marrelli
(Consorzio RFX, Padova, Italy)
Luca Grando
(Consorzio RFX, Padova, Italy)
Paolo Bettini
(Consorzio RFX, Padova, Italy)
Paolo Zanca
(Consorzio RFX, Padova, Italy)
Piergiorgio Alotto
(DII, Università di Padova, Via Gradenigo, 6/A, Italy)
Roberto Cavazzana
(Consorzio RFX, Padova, Italy)
Ruben Specogna
(DPIA, Università di Udine, via delle Scienze, 206, Italy)
Tommaso Bolzonella
(Consorzio RFX, Padova, Italy)
