High energy Neutral Beam Injection (NBI) is one of the methods being considered in EU DEMO pre-conceptual design phase to provide auxiliary power to the plasma. From recent studies [1], it appears clear that auxiliary heating power is needed during the ramp-up (and ramp-down) phase to guarantee a robust access to H-mode (and to compensate for high radiation power losses in ramp-down). The use of NBI during ramp-up has to be carefully considered due to possible shine-through losses which can exceed the maximum heat load tolerated by the first wall (for DEMO the steady state peak heat flux limit is 1 MW m-2 [2]). In ITER, shine-through losses pose a lower limit on density for NBI operation at n~3x1019 m-3 [3]. This limits for ITER the operational window of the NBI system and can prevent its use during the ramp-up phase due to low plasma density. In this work the heat wall loads due to NBI shine through and orbit losses are calculated for the diverted plasma ramp-up phase of EU DEMO pulsed scenario by numerical simulations performed by BBNBI [4] and ASCOT [5] Monte Carlo codes. The simulations have been done in a complete 3D geometry considering the latest DEMO NBI design [6], which foresees NBI at 800 keV energy with respect to 1MeV beam energy for ITER. Location and power density of NBI-related heat loads at different time-steps of DEMO ramp-up are evaluated and compared with the maximum heat flux limit. Since NBI shine-through losses depends mainly on the beam energy, plasma density and volume, DEMO has a more favorable situation than ITER, enlarging NBI operational window. This increases the appeal of neutral beam injectors as auxiliary power systems for DEMO.
Estimate of 3D wall heat loads due to Neutral Beam Injection in EU DEMO ramp-up phase
Agostinetti P;
2018
Abstract
High energy Neutral Beam Injection (NBI) is one of the methods being considered in EU DEMO pre-conceptual design phase to provide auxiliary power to the plasma. From recent studies [1], it appears clear that auxiliary heating power is needed during the ramp-up (and ramp-down) phase to guarantee a robust access to H-mode (and to compensate for high radiation power losses in ramp-down). The use of NBI during ramp-up has to be carefully considered due to possible shine-through losses which can exceed the maximum heat load tolerated by the first wall (for DEMO the steady state peak heat flux limit is 1 MW m-2 [2]). In ITER, shine-through losses pose a lower limit on density for NBI operation at n~3x1019 m-3 [3]. This limits for ITER the operational window of the NBI system and can prevent its use during the ramp-up phase due to low plasma density. In this work the heat wall loads due to NBI shine through and orbit losses are calculated for the diverted plasma ramp-up phase of EU DEMO pulsed scenario by numerical simulations performed by BBNBI [4] and ASCOT [5] Monte Carlo codes. The simulations have been done in a complete 3D geometry considering the latest DEMO NBI design [6], which foresees NBI at 800 keV energy with respect to 1MeV beam energy for ITER. Location and power density of NBI-related heat loads at different time-steps of DEMO ramp-up are evaluated and compared with the maximum heat flux limit. Since NBI shine-through losses depends mainly on the beam energy, plasma density and volume, DEMO has a more favorable situation than ITER, enlarging NBI operational window. This increases the appeal of neutral beam injectors as auxiliary power systems for DEMO.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
