Suppression of the Transit-Time Instability in Large-Area Electron Beam Diodes
Abstract
Experiment, theory, and simulation have shown that large-area, electron-beam diodes are susceptible to transit-time instability. The instability modulates the electron beam spatially and temporally, producing a wide spread in electron energy and momentum distributions. The result is gross inefficiency in beam generation and propagation. Simulations indicate that a periodic, slotted cathode structure that is loaded with resistive elements may be used to eliminate the instability. Such a cathode has been fielded on one of the two opposing 60 cm x 200 cm diodes on the NIKE Krypton-fluoride (KrF) laser at the Naval Research Laboratory. These diodes typically deliver 600 kV, 500 kA, 250 ns electron beams to the laser cell in an external magnetic field of 0.2 T. The authors conclude that the slotted cathode suppressed the transit-time instability such that the radiofrequency power was reduced by a factor of 9 and that electron transmission efficiency into the laser gas was improved by more than 50%.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2002
- Accession Number
- ADA480617
Entities
People
- John D. Sethian
- Larry Ludeking
- Lop-yung Chan
- Matthew C. Myers
- Moshe Friedman
- Stephen B. Swanekamp
Organizations
- United States Naval Research Laboratory