Particle Charging in DC Corona Fields
After a brief review of the currently accepted theory of particle charging in corona fields in air by both ionic bombardment and diffusion in the dark space surrounding the dc corona glow, the paper presents some of the recently published findings on particle charging within the corona glow. The study was made possible by the discovery that additions of CO2 to air in a 5 to 20% range will increase a cylindrical positive corona glow to a size which is sufficiently large to allow particles to be dropped on to various trajectories parallel to the corona wire and their charge to be measured. The influence of the shape of the particles when exposed to corona charging is also discussed.
Rate of charging of spherical particles by monopolar ions in electric fields
This paper presents a numerical algorithm to simulate the charging dynamics of high-resistivity spherical particles by the ionic bombardment in an electric field. The algorithm is based on solving the Poisson equation, governing the electric field distribution, and the differential equation expressing the charge conservation law. The Poisson equation is solved be means of the finite-element method using the triangular discretization and the first of interpolation. The finite-volume method (in a version called the donor-cell method) is used to handle the charge conservation equation. Results of simulation are also presented and they illustrate the effect of different parameters on the charging dynamics. For high-conductivity particles, the charging rate is practically identical to that given by the Pauthernier formula. Charging of high-resistivity particles leads to more complicated solutions and is much slower.
Investigation of scatter radiation of non-circular X-ray scan trajectories
Modern interventional X-ray devices are highly maneuverable and allow complex 3D imaging trajectories. New scan trajectories enable not only optimized object sampling but also introduce new approaches for dynamic 3D imaging. In this paper, we investigated the scatter radiation of two different scan trajectories. The scatter radiation was sampled by a rail setup with dosimeters at defined positions. After data analysis, contour maps were generated which show for four exemplary heights the scatter radiation distribution. The alternative scan trajectory showed smaller dose exposures at heights correlated to upper torso and head areas of a model physician. Keywords—Image acquisition, alternative scan trajectory, circular tomosynthesis, scatter radiation distribution