Ionization Waves in a Shielded Capillary Discharge in the Presence of Runaway Electrons
Abstract
The prebreakdown stage of the evolution of a VUV-soft X-ray emitting capillary discharge initiated by a high-voltage pulse is studied. The capillary is surrounded by a shield having the cathode potential. For low initial gas pressure most of the electrons are in the runaway regime. This is taken into account in the formulation of the theoretical approach by retaining the inertial terms in the momentum equation for the electrons. In addition, the ionization rate is calculated by considering the cross section for ionization by high-energy electrons. The two-dimensional system of the basic equations is reduced to a one-dimensional system of equations for the axial distribution of the relevant physical quantities by introducing appropriate radial profiles of the electric potential and the electron velocity, and satisfying the boundary conditions at the capillary wall. The resulting system of equations admits solutions of the form of stationary ionization waves transferring the anode potential to the cathode end. The theoretical results are correlated with the time-resolved experimental studies of the voltage collapse associated with the hollow-cathode-assisted ionization growth in the capillary.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1998
- Bibcode:
- 1998APS..DPP.B1F12R