Adam Stahl

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In this Letter we investigate factors that influence the effective critical electric field for runaway-electron generation in plasmas. We present numerical solutions of the kinetic equation and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway-electron formation often is(More)
Test particles infalling from infinity onto a compact spherical star with a mildly super-Eddington luminosity at its surface are typically trapped on the “Eddington Capture Sphere” and do not reach the surface of the star. The presence of a sphere on which radiation pressure balances gravity for static particles was first discovered some twenty five years(More)
We analyze the dynamics of fast electrons in plasmas containing partially ionized impurity atoms, where the screening effect of bound electrons must be included. We derive analytical expressions for the deflection and slowing-down frequencies, and show that they are increased significantly compared to the results obtained with complete screening, already at(More)
We introduce a modified method of powder-diffraction data analysis to obtain precise structural information on freestanding ZnS and CdS nanoparticles with diameters well below 5 nm, i.e., in a range where common bulk-derived approaches fail. The method is based on the Debye equation and allows us to access the crystal structure and the size of the particles(More)
Highly relativistic runaway electrons are of great concern in the area of fusion energy research, since their presence in tokamak plasmas have the potential to hinder the successful and stable operation of the device, and potentially cause severe structural damage. In this thesis, runaway electron generation dynamics is investigated using the newly(More)
Energetic electrons are of interest in many types of plasmas, however previous modeling of their properties has been restricted to the use of linear Fokker–Planck collision operators or non-relativistic formulations. Here, we describe a fully non-linear kinetic-equation solver, capable of handling large electricfield strengths (compared to the Dreicer(More)
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