The Trial Lecture will take place 10:15 - 11:15.
The title of the Trial Lecture is:
« ExB Staircases in Tokamak Plasma Edges: Theoretical Models, Numerical Simulations, and Experimental Signatures »
The Thesis Defense will take place 12:15 - 15:00.
The title of the thesis is:
« Turbulence and Transport in the Boundary of Fusion Plasmas: Fluid Modeling, Numerical Simulations, and Statistical Analysis »
Turbulence remains a fundamental open problem in physics and mathematics. Although its governing equations may be deterministic, its nonlinear and multiscale dynamics produce irregular behaviour most naturally described through statistical methods. Magnetically confined fusion plasmas provide a physically important setting in which to investigate this problem.
In the scrape-off layer (SOL), strong gradients drive turbulence characterized by coherent filamentary structures, intermittency, and transport across magnetic field lines that cannot generally be represented by effective diffusion alone. These processes also determine particle and heat exhaust, plasma–wall interactions, and the lifetime of plasma-facing components.
Developing predictive descriptions of their formation, propagation, and statistical behaviour is therefore essential for the design and operation of future fusion devices.
This thesis investigates turbulence-driven transport in the SOL using reduced two-field drift-fluid simulations, three-dimensional full-$F$ gyrofluid simulations, and stochastic modelling. The focus being on the relationship between nonlinear turbulence dynamics, intermittent filamentary structures, and reproducible statistical properties. The work examines how parallel particle losses and sheath dissipation influence turbulence, radial density profiles, and filament dynamics. In the reduced fluid model, increased parallel losses and sheath dissipation produce steeper density profiles and shift fluctuations towards smaller spatial scales. Although these mechanisms affect instability growth, fluctuation amplitudes, and blob properties differently, the fluctuation statistics of the turbulent fluctuations remain robust.
Synthetic probe signals extracted from the simulations are analysed through probability density functions, power spectral densities, conditional averaging, and deconvolution methods. Both reduced and three-dimensional simulations reproduce central statistical signatures observed in SOL experiments: order-unity intermittent fluctuations in plasma quantities, positively skewed non-Gaussian distributions, asymmetric exponential burst waveforms, and frequency spectra consistent with the stochastic framework based on filtered Poisson processes. These findings demonstrate how robust stochastic behaviour can emerge from deterministic nonlinear fluid and gyrofluid models.
The filtered Poisson process provides a compact framework in which fluctuations are described by superposition of independently arriving filamentary events. Deconvolution analysis shows that the time-averaged density profile can be reconstructed from the pulse population, directly connecting macroscopic profile formation to intermittent transport. A comparatively small fraction of large-amplitude, rapidly propagating filaments carries a substantial fraction of the radial particle flux. Three-dimensional gyrofluid simulations further reveal ballooning transport and curved, non-field-aligned filament structures whose behaviour depends on magnetic-field direction and parallel dynamics.
Together, the results establish SOL turbulence as a useful system for investigating the interplay between nonlinear dynamics, coherent structures, transport, and stochastic statistics.
They show that reduced and gyrofluid models capture important physical and statistical features of intermittent turbulence, while stochastic pulse models provide a bridge between turbulence simulations, filament dynamics, and experimentally accessible measurements.
The Trial Lecture and Thesis Defense will be streamed via Panopto:
Trial Lecture (10:15 - 11:15)
Watch the Trial Lecture
Thesis Defense (12:15 - 15:00)
Watch the Thesis Defense
The thesis is available in Munin: