Speaker
Description
Plasma start-up is a critical phase in tokamak operation and becomes particularly challenging in superconducting devices such as ITER, where the low toroidal electric field (E ∼ 0.3 V m⁻¹), stray poloidal fields, and residual impurities constrain ohmic initiation and can result in either breakdown failure or radiation-limited burn-through. Electron Cyclotron (EC) waves can mitigate these limitations by providing localized pre-ionization, assisting burn-through, and facilitating the initial current formation.
This contribution reviews recent experimental and numerical results from the CNR-ISTP group. Early studies on FTU addressed fundamental aspects of plasma formation [1], while investigations on TCV and ASDEX Upgrade [2] expanded these insights. On JT-60SA [3], the largest superconducting tokamak in operation prior to ITER, the effects of Trapped Particle Configurations (TPCs) and Field Null Configurations (FNCs) on EC-assisted start-up were explored, highlighting the role of magnetic topology in breakdown dynamics and burn-through efficiency. Complementary numerical modelling provides a basis for interpreting these results and extrapolating them to ITER [4], accounting for the influence of impurities, EC assistance, and electromagnetic constraints, thereby supporting the robust design of start-up scenarios.
Reference:
[1] G. Granucci et al 2015 Nucl. Fusion 55 093025
[2] Ricci D, EPJ Web Conf. 277 02001
[3] T. Wakatsuki et al 2024 Nucl. Fusion 64 104003
[4] X. Litaudon et al 2024 Nucl. Fusion 64 112006
