Eric Held

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Utah State University

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Nuclear fusion converts the rest mass energy of ions like the deuteron and triton into kinetic energy. In theory, this energy can be harvested from a thermonuclear reactor to provide power outputs on the scale of 500 MW. High temperatures are needed for significant fusion to occur, hence the tokamak (a modern fusion confinement device) employs strong magnetic fields to keep the ionized gas (plasma) away from the tokamak wall. However, a problem that occasionally arises in a tokamak is that during a disruption an inductive electric field is created which can accelerate electrons to relativistic speeds (these electrons are called runaway electrons (RE’s)). The magnetic field lines also become stochastic (volume-filling) and can intersect with the wall. Following magnetic field lines, RE’s are led to and can obliterate the expensive plasma facing components (PFC’s). This work involves getting the physics of RE’s into NIMROD, a plasma-fluid code. Overall, this is a very large and complex problem so we will focus on seeing if NIMROD’s relativistic electron model agrees with other 2D phase-space codes in terms of how the electrons get accelerated. This involves looking at the different processes: acceleration by the inductive electric field, the drag force associated with colliding off the background plasma, and the release of energy through synchrotron radiation. Considering all of this we want to see if NIMROD can predict/calculate a balance of these forces to lead to a steady state vortex pattern in the relativistic phase-space.

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