Fusion Engineering and Design 88 (2013) 1091–1096 Contents lists available at ScienceDirect Fusion Engineering and Design journal h om epa ge: www.elsevier.com/locat e/fusengdes Linearized models for a new magnetic control in MAST G. Artaserse a,∗ , F. Maviglia b , R. Albanese b , G.J. McArdle c , L. Pangione c a Associazione Euratom-ENEA sulla Fusione, Via Enrico Fermi 45, I-00044 Frascati (RM), Italy b Associazione Euratom-ENEA-CREATE sulla Fusione, Via Claudio 21, I-80125 Napoli, Italy c EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK h i g h l i g h t s ◮ We applied linearized models for a new magnetic control on MAST tokamak. ◮ A suite of procedures, conceived to be machine independent, have been used. ◮ We carried out model-based simulations, taking into account eddy currents effects. ◮ Comparison with the EFIT flux maps and the experimental magnetic signals are shown. ◮ A current driven model for the dynamic simulations of the experimental data have been performed. a r t i c l e i n f o Article history: Available online 4 February 2013 Keywords: MAST Linearized model Tokamak Magnetic control Equilibrium State space model a b s t r a c t The aim of this work is to provide reliable linearized models for the design and assessment of a new magnetic control system for MAST (Mega Ampère Spherical Tokamak) using rtEFIT, which can easily be exported to MAST Upgrade. Linearized models for magnetic control have been obtained using the 2D axisymmetric finite element code CREATE L. MAST linearized models include equivalent 2D axisymmetric schematization of poloidal field (PF) coils, vacuum vessel, and other conducting structures. A plasmaless and a double null configuration have been chosen as benchmark cases for the comparison with experi- mental data and EFIT reconstructions. Good agreement has been found with the EFIT flux map and the experimental signals coming from magnetic probes with only few mismatches probably due to broken sensors. A suite of procedures (equipped with a user friendly interface to be run even remotely) to provide linearized models for magnetic control is now available on the MAST linux machines. A new current driven model has been used to obtain a state space model having the PF coil currents as inputs. Dynamic simulations of experimental data have been carried out using linearized models, including modelling of the effects of the passive structures, showing a fair agreement. The modelling activity has been useful also to reproduce accurately the interaction between plasma current and radial position control loops. © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved. 1. Introduction MAST is a spherical tokamak (ST), which presents a compact “cored apple” shape and a lower aspect ratio, up down symmet- ric usually operating in a double null divertor (DND) magnetic configuration. Plasmas with elongated cross section are vertically unstable hence subjected to vertical displacement events (VDEs) which affecting the tokamaks operation [1,2]. MAST is equipped with extensive and advanced diagnostics, with a digital control sys- tem which includes density feedback control and a novel optical system for plasma radial position control. Real time equilibrium reconstruction, based on rtEFIT [3], has been deployed in the ∗ Corresponding author. Tel.: +39 06 9400 5906; fax: +39 06 9400 5735. E-mail address: giovanni.artaserse@enea.it (G. Artaserse). control system. Reliable linearized models are necessary for the design and assessment of a new magnetic control system for MAST using rtEFIT, which can easily be exported to MAST Upgrade. In Section 2 of this paper the MAST machine modelling activity is introduced. The porting of the XSCTools to MAST is treated in Section 3. Benchmark cases are analyzed in Section 4 with dynamic simulations including eddy currents, comparing the model predic- tions with flux map reconstructions and experimental magnetic signals. Summary and conclusions are given in Section 5. 2. MAST modelling MAST has a central solenoid (P1), which provides the magnetic flux used to control the plasma current, and a set of up down symmetric PF coil sets (as shown in Fig. 1) connected by six inde- pendent circuits. The P2 coil can be used to achieve the desired DND 0920-3796/$ – see front matter © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2012.12.033