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Abstract
In modern, highly optimized stellarator configurations where prompt fusion alpha particle losses from the plasma core are absent, alpha particles can still be lost due to stochastic orbits which result in delayed losses. One mechanism leading to stochastic orbits are changes in the particle trapping class during drift motion along the contours of the parallel adiabatic invariant J∥ leading to jumps in J∥ when crossing class boundaries. Another mechanism, which is of main interest here, is the resonance between particle drift and bounce motion (driftorbit resonance). The first mechanism affects mainly trapped particles near the trappedpassing boundary in the phase space of quasisymmetric and quasiisodynamic devices, and can be minimized there by aligning local magnetic field maxima on a given flux surface. The second mechanism may affect a broader range in the trapped particle domain where contours of J∥ still remain closed. Driftorbit resonances modify the topology of orbits leading to islandlike structures on Poincaré plots where these islands may overlap thus leading to the stochastic transport. In this report, we study this stochastization mechanism in quasisymmetric stellarator configurations with help of the Hamiltonian driftkinetic code NEORT as well as orbit classification and direct computation of fusion alpha losses within the symplectic orbit following code SIMPLE. The width and overlap of resonances in phasespace is studied using Hamiltonian perturbation theory. Based on optimized reactor configurations we assess if this approach can be used as a fast metric for fusion alpha losses in stellarator optimization
Original language  English 

Article number  012009 
Journal  Journal of Physics: Conference Series 
Volume  2397 
Issue number  1 
DOIs  
Publication status  Published  1 Dec 2022 
Event  2022 Joint VarennaLausanne International Workshop on the Theory of Fusion Plasmas: VarennaLausanne 2022  Varenna, Italy Duration: 11 Sep 2022 → 16 Sep 2022 
ASJC Scopus subject areas
 Physics and Astronomy(all)
Fields of Expertise
 Sustainable Systems
 Information, Communication & Computing
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EUROFusion  Transport and Heating in Fusion Plasmas
Kernbichler, W., Albert, C., Eder, M., Kasilov, S., Markl, M., Buchholz, R., Graßler, G. S., Kamendje, R. L., Babin, R. & Lainer, P.
1/01/21 → …
Project: Research project