ASCOT simulations of fast ion power loads to the plasma-facing components in ITER

Abstract

The wall loads due to fusion alphas as well as neutral beam injection- and ICRF-generated fast ions were simulated for ITER reference scenario-2 and scenario-4 including the effects of ferritic inserts (FIs), test blanket modules (TBMs), and 3D wall with two limiter structures. The simulations were carried out using the Monte Carlo guiding-centre orbit-following code ASCOT. The FIs were found very effective in ameliorating the detrimental effects of the toroidal ripple: the fast ion wall loads are reduced practically to their negligible axisymmetric level. The thermonuclear alpha particles overwhelmingly dominate the wall power flux. In scenario-4 practically all the power goes to the limiters, while in scenario-2 the load is fairly evenly divided between the divertor and the limiter, with hardly any power flux to other components in the first wall. This is opposite to earlier results, where hot spots were observed with 2D wall (Tobita et al 2003 Fusion Eng. Des. 65 561–8). In contrast, uncompensated ripple leads to unacceptable peak power fluxes of 0.5 MW m−2 in scenario-2 and 1 MW m−2 in scenario-4, with practically all power hitting the limiters and substantial flux arriving even at the unprotected first wall components. The local TBM structures were found to perturb the magnetic field structure globally and lead to increased wall loads. However, the TBM simulation results overestimate the TBM contribution due to an over-simplification in the vacuum field. Therefore the TBM results should be considered as an upper limit.

Effects of complex symmetry-breakings on alpha particle power loads on first wall structures and equilibrium in ITER

“…10 the belt of large power flux is found at about 50 degrees below the poloidal angle. This is in contrast to previous works where only little power was observed in this region for the same 3D vacuum magnetic field but somewhat different wall shape [14], and for somewhat different magnetic field and somewhat different wall shape [3]. Thus the power load clearly depends on the first wall shape.…”

“…In fact, the results of Ref [7] by OFMC and HYBRID codes revealed the importance of the reduction of TF ripple in ITER, and the installation of FI was proposed. Also the full orbit-following code, SPIRAL [10], has been used for confinement studies, while preliminary results for the power loads on ITER wall structures were obtained using ASCOT [3].…”

Sawtooth control in ITER using ion cyclotron resonance heating

“…In order to model the neutral beam fast ion distribution, the TRANSP [25] and ASCOT [26,27] codes have been used. ASCOT has been used to model the alpha particle population whilst SELFO [28], SCENIC [29,30] and a coupling of AORSA [31] with CQL3D [32] have been used to simulate the ICRH distribution.…”

First absolute measurements of fast-ion losses in the ASDEX Upgrade tokamak

“…2 ). The NBI prompt losses in this discharge have been modeled with the full orbit code ASCOT [8]. 10 6 test particles were followed until they hit a plasma facing component or slow down to the background thermal energy.…”