University of Heidelberg

PhD Projects


Hybrid plasma simulations for the KATRIN experiment

The astroparticle-physics experiment KATRIN involves a beam tube filled with plasma. In order to understand the experimental resulted it is inevitable to model the plasma. The challenge here is that different physical effects (ionisation, recombination, plasma-wall interaction) come into play and that plasma itself is stronly inhomogenous. Multi-scale and multi-physics models are therefore needed.

A Monte Carlo model for atomic and molecular processes as well as independent fluid and kinetic models have been developed in preceding theses. Starting point for this thesis is the Particle-in-Cell model for the plasma. From there a hybrid model shall be established that allows to model high and low density parts of the plasma simultaneously. The ultimate goal is to establish a physically correct representation of the plasma potential. That will be the basis for the evaluation of experimental results.

A major part of the work will be devoted to numerical methods - a profound knowledge of C++ is beneficial. Basic knowledge in fluiddynamics, plasmaphysics or electrodynamics is a plus.

Scientific environment: KATRIN

The international Karlsruhe Tritium Neutrino (KATRIN) experiment aims at measuring the fundamental mass scale of electron neutrinos with a sensitivity of 200 meV. The heart of the experiment is 10 m long beam tube that is the windowless source of high energy β electrons. These electrons originate from neutral tritium injected into the beam tube, that is pumped off at both ends. Through a series of complicated secondary electron production mechanisms a plasma forms inside the tube. The electric plasma potential has an impact on the initial energy of the primary β electrons, which in turn affects the neutrino mass measurement. Unfortunately a direct measurement of the plasma potential is imposible. Detailed simulations are therefore necessary. The key ingredient to these simulations is the electron energy distribution.

Cross sections of atomic processes

Experimental environment: Windowless tritium source

Within the windowlss tritium source the neutral gas is ionized by β decay electrons. Through elastic and inelastic colision these electrons cool down to the ambient gas temperature. Within this masters project a more refined model of electron-gas interaction will be implemented. The goal is to determine the electron- and ion-energy distribution at every point within the source.

Responsible: Felix Spanier, last modification Oct/12/2020 14:23 CEST
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