ITER Plasma Vertical Stabilization

In this paper we summarize the results of the modelling, analyses and assessment of the ITER Vertical Stabilization (VS) system design carried out in the last two years by the ITER IO and Domestic Agencies as well as its possible improvements: these include the use of an additional VS system connecting some of the Central Solenoid coils, a power supply upgrade from 6 kV to 9kV, the use of passive stabilizers and in-vessel active coils. The assessment is performed on the basis of key figures of merit that are, in most cases, dimensionless and feedback control independent thus allowing ITER to be compared to present day experiments. On the basis of these indicators, different design solutions for possible VS system upgrades are compared. Experimental guidance is of key importance to understand the level to which present-day machines are able to push their VS systems without increased frequency of VDEs and experimental data are presented. Conclusions and recommendations are given for an integrated use of in-vessel active coils for the control of axi-symmetric and higher order modes.