Book/Dissertation / PhD Thesis

FZJ-2018-02072

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Entwicklung eines Werkzeugs zur Modellierung der Nettoerosion im Hauptraum der Brennkammer eines Tokamaks und Studium der Plasma-Wand-Wechselwirkung an DEMO1

Beckers, M. (Corresponding author)FZJ*

2018
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-307-5

Please use a persistent id in citations: http://hdl.handle.net/2128/18018  urn:nbn:de:0001-2018050970

Abstract: Thermonuclear fusion is a promising concept for safe, sustainable, environmental friendly and expandable electricity production on earth. DEMO1 is the working title of a $\textit{european demonstration power plant}$, which is being developed and foreseen to be operated by the year 2050. The $\textit{early design phase}$ lasts until 2021. According to the current $\textit{baseline scenario}$, DEMO1 will be a tokamak with two hours of pulse duration and five hundred megawatts of electrical output power. $\textit{Design points}$, i.e. an optimized set of machine and plasma parameters, are obtained by fast 0.5d reactor $\textit{system codes}$ that constrain the parametric space by physics- and technology-limits. Aspects of $\textit{plasma-wall-interaction}$ in the main chamber have not yet been included into suchcodes. Well established and sophisticated codes for plasma edge modeling such as EIRENE (neutral particle kinetics), B2 (plasma dynamics) and ERO (eroded wall material) have so far been unavailable and incompatible with system modeling. One major scientific goal of this thesis was the development of a tool, for a description of the stationary global net erosion of a tungsten-armored first-wall in the main chamber of a fusion reactor, that allows inclusion in system modeling. Another goal was the identification of plasma edge parameters for the current DEMO1 baseline scenario, yielding acceptable erosion rates. For feasibility it was demanded, that at least ninety percent of the plasma-facing, protective, pure-tungsten-layer must persist the erosion by impinging ions and atoms during the scheduled time-of-operation of the starter- and follow-up blanket. For a calculation of the neutral particle kinetics and the wall-sputtering by fuel neutrals, the 1d monte-carlo CELLSOR-code was developed and benchmarked with the EIRENE-code, i.e. the european tool for modeling of the ITER-divertor. CELLSOR solves kinetic equations in a 7d phase space with a 1d plasma description and physical rate coeficients for atomic and molecular interactions. CELLSOR calculates the angle- and energy-dependent sputter yields at wall-incidence. For modelling of plasma fuelling, a new pellet ablation model was developed. The CELLSOR ERO extension was developed for calculations of prompt redeposition and selfsputtering of eroded tungsten atoms. Particle balance within the $\textit{scrape-off-layer}$ (SOL) was calculated by an analytic solution of the continuity equation in a 1.5d fluid description with an iterative algorithm for coupling to the results of the kinetic solution. The required external fuelling flux was calculated from flux balance euqations at the boundary between the confined core and the SOL. For calculations of the damage by ions, i.e. fuel (D,T), $\textit{ash}$ (He), $\textit{seeding gas}$ (N) and eroded surface material (W), a 0d sheath-approximation model was developed. With these tools, the global net erosion was calculated for distinguished testcases for variations of the size of the wall clearance and for both, diffusive and convective transport perpendicular to the magnetic field lines. The testcases were mainly differing in the pedestal pressure, i.e. density and temperature, and the separatrix density levels. It was shown, that on DEMO1, other than on present tokamaks, the damage of the first-wall was almost completely due to light fuel neutrals, which were released towards the first-wall by charge exchange (CX) collisions in the hot pedestal region, due to the strong external fuelling of the core edge plasma. On the contrary, the ion damage was sufficiently reduced by a wall clearance of a few centimetres. [...]

Note: Universität Düsseldorf, Diss., 2017

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Contributing Institute(s):

1. Plasmaphysik (IEK-4)

Research Program(s):

1. 174 - Plasma-Wall-Interaction (POF3-174) (POF3-174)

Appears in the scientific report 2018

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