Transition from laminar to space charge dominated flow in a low energy electron beam in ELTRAP.
Abstract
The dynamics of a low energy electron beam is studied in the Malmberg-Penning trap ELTRAP, where an electron plasma continuously flows from the emitting thermionic cathode to a collector (phosphor screen), held at a potential of few kV. The transition from a laminar to a space charge dominated flow is characterized by the formation of a reflection surface which prevents the central part of the beam from reaching the screen, and by the rapid development of seemingly 2D coherent structures in the resulting annular beam. The experimental investigation is performed by means of a CCD camera diagnostic, which allows to measure the density distribution of the electrons reaching the phosphor screen. It is shown that the transition corresponds to a bifurcation of the system. The observed processes are interpreted using fluid models and a recently developed 3D drift-Poisson PIC code.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPBP1049P