Jonatan Schatzlmayr
Within fusion devices, various transport processes lead to complicated dynamics that are not yet well understood, but can become detrimental to reactor performances. Various models exist to simulate these dynamics, with the most accurate ones going down to the kinetic description of single particle trajectories. While this approach is usually computationally extremely demanding, the code GORILLA (acronym for Guiding Center Orbit Integrator with Local Linearization approach) developed at Graz University of Technology outperforms competing codes by up to an order of magnitude in terms of computer performance, while achieving similar degrees of accuracy. This talk explains the working mechanisms of GORILLA and discusses some of its properties and recently developed features. In specific, the concept of symplecticity will be introduced and the implementation of a stochastic collision operator discussed. Furthermore, the computation of self-consistent stationary electric fields in arbitrary magnetic fields will be investigated.
Georg Grassler
Stellarators are devices used in nuclear fusion to confine plasma via 3D magnetic fields. The bootstrap current is a particle current in these devices driven by the pressure gradient between the hot plasma core and "cold" plasma edge. This current is influenced by the magnetic field geometry and in term itself changes the magnetic field via Amperes Law. Stellartor fields often have so-called "quasi-symmetries", i.e. the magnetic field strength does not change when moving in the symmetry direction. These symmetries can be leveraged to efficiently compute the bootstrap current. However, in reality there are no perfect quasi-symmetric devices. This violation of the symmetries leads to a divergence of the bootstrap current as the plasma gets hotter and the collisions between particles gets rarer.
Here we present semi-analytical formula [1] that allow for a calculation of this offset due to symmetry-breaking with low computational cost. A numerical implementation is presented as well as benchmarks with state-of-the-art, but computational expensive codes (NEO-2 [2] and DKES [3]) that directly solve the full kinetic system instead.
[1] C.G. Albert et al., arXiv:2407.21599v3 [physics.plasm-ph] (2025)
[2] W. Kernbichler et al., Plasma Phys. Control. Fusion, 58(10):104001 (2016)
[3] S. P. Hirshman et al., Phys. Fluids, 29(9):2951–2959, (1986)
Philipp Zenz
Fusion energy is a promising candidate for future clean energy source with low carbon emissions Achieving the conditions required for nuclear fusion, however, remains highly challenging. The most advanced approach to plasma confinement relies on strong magnetic fields in a device known as tokamaks High-performance plasmas in tokamaks are often limited by various instabilities, which become increasingly severe when extrapolated to reactor-scale devices. One such instability is known as edge localized mode (ELM) and must be mitigated or suppressed to guarantee a reasonable lifetime of a reactor.
It has been experimentally shown that one way to suppress ELMs is to apply 3D magnetic perturbations to the plasma. This however comes with a number of side effects including neoclassical toroidal viscosity (NTV) which modulates the rotation profile of the plasma. This is a key effect as a too small rotation of the plasma can lead to a global instability of the plasma. Therefore accurate modelling of NTV is necessary to assess the feasibility of magnetic perturbation (MP) ELM suppression.
Sanjay John
1,1ˈ-Binaphthyl is an axially chiral molecule that crystallizes in either racemic phase, consisting of equal number of both enantiomers in the unit cell or in a chiral phase where only one type of enantiomer is present in the unit cell. These two phases arise from distinct molecular conformers, a cis conformer with a dihedral angle of 68.6° characteristic of the racemic phase and a trans conformer with a dihedral angle of 103.1° characteristic of the chiral phase. Thin film crystallization of binaphthyl in the chiral phase can be achieved introducing non-equilibrium conditions. Thin film crystallization kinetics are strongly influenced by the presence of a solid substrate, where selective adsorption of the trans conformer at the substrate–liquid interface drives nucleation and promotes complete chiral phase formation. In contrast, nucleation of the cis conformer at the air–liquid interface often leads to the crystallization in the racemic phase. Spatially resolved Mueller Matrix Polarimetry (MMP) is an ideal tool to probe the chirality in thin films and has been deployed for localized circular dichroism mapping on binaphthyl thin films. Furthermore, selective adsorption of a specific enantiomer over large domains can be achieved using a tailored additive approach, with the resulting chiral purity and spatial distribution confirmed through CD mapping.