Particle-in-Cell Simulations of Large-Area Electron Beam Diodes for KrF Laser Driven IFE
Abstract
Large-area electron beam diodes are being developed to pump high-power krypton-fluoride (KrF) lasers that are suitable for inertial fusion energy. In a recent paper it was shown that the electron beam diode used on the Nike laser at NRL is susceptible to the transit time instability.(M. Friedman, S. Swanekamp, S. Obenschain, Y. Chan, L. Ludeking, and D. Smithe, Appl. Phys. Lett. 77), 2000 (1053). This instability introduces an energy spread on the electron beam as it leaves the diode. In this paper, we will show that experiments with the smaller diode used on the Electra laser are not affected by the transit time instability. We will show analysis and simulations that support these experimental observations that indicate growing waves are supported only when wave growth in the diode exceeds the losses out the ends of diode. We will further show that there is a critical diode length, L_crit, for which the diode in unstable when L > L_crit. We will also show that the growth rate is proportional to L√V/d^2 where L is the diode length, V is the voltage, and d is the anode-cathode gap spacing.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2001
- Bibcode:
- 2001APS..DPPQO2012S