Master's Thesis Defense by Aslak Sinding Poulsen – Niels Bohr Institute - University of Copenhagen

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Master's Thesis Defense by Aslak Sinding Poulsen

Title: Investigation of Plasma Blobs

Abstract: The motion of localized density filaments known as plasma blobs in magnetized fusion plasmas is studied using a fully kinetic particle-in-cell (PIC) code. We review basic plasma theory that is needed to understand the general physical aspect of the numerical PIC code. Following this, the blob concept is defined in detail, and a scaling law based on fluid considerations is derived. The PIC code is based on the electromagnetic Photon-Plasma code developed at NBI and has been modified to an electrostatic version that keeps the magnetic field constant and solves Poisson's equation to obtain the electric field. Both are described in detail.

With the PIC code we investigate the driving mechanism of the blob motion in a two dimensional domain perpendicular to the magnetic field. Here we find that the driving is most likely caused by a magnetic gradient drift followed by an electric drift. Furthermore, finite Lamor radius effects are investigated and found to be heavily influenced by the ion temperature. The scaling laws have been tested in details and it is shown that the kinetic approach for a large part follows the scaling laws.

Supervisor: Jacob Trier Frederiksen