Computations of AC Loss in the ITER Magnets during Fast Field Transients

The calculation of AC loss due to the control currents in ITER is a cumbersome task. The reason is that control transients require small field changes (0.1 T or less) at moderate frequency (up to 10 Hz), where effects of partial penetration of the filaments and shielding are important and need to be taken into account to produce sound AC loss estimates. In this paper we describe models developed for AC loss calculation, in particular hysteresis and coupling current loss, that are suitable for the above regime. Both hysteresis and coupling loss models are adapted to the conductor analyzed through few parameters (the effective filament diameter and time constants) that can be derived from measurement of loss on short samples. We report an example of calculations of AC loss in the ITER TF and PF coils for two vertical control scenarios (VS1 and VS2) during high beta operation at flattop.