Pulsed Power Design for a Small Repetitively Pulsed Electron Beam Pumped KrF Laser

Electra is a 700 J, repetitively pulsed, electron beam pumped Krypton Fluoride (KrF) laser that is developing technologies to meet the inertial fusion energy (IFE) requirements for rep-rate, efficiency, durability and cost. We have designed a pulsed power system for the pre-amplifier in the Electra KrF laser system. This pre-amplifier is designed to produce 40 J of laser light in a 40 nsec pulse which will be used to provide the input to the main amplifier. The pulsed power for the front end will serve two roles. It will complete the laser system and it will serve as the demonstrator for the new advanced pulsed power topology that can meet the fusion energy requirements for durability, repetition rate, and cost. The pulsed power will first employ a gas-switched Marx, with anticipated maintenance intervals similar to that of the existing Electra main amplifier. Later the driver will be replaced (circa 2006) with a solid-state-switched Marx generator. The pulser will operate in single-shot, burst, and continuous modes up to 5 pps, with 1 nsec (1 sigma) or less absolute timing jitter. Rather than build an individual driver for each e-beam diode as was done for the Electra main amplifier, a single pulsed power driver is coupled to the opposing electron guns via four liquid-filled Transit Time Isolators (TTIs). The Marx is gas-insulated and charges a 1.1-ohm water pulse forming line (pfl) in less than 100 nsec. An output magnetic switch with a saturated inductance of less than 14 nH discharges the pfl into the four parallel TTIs. A set of four (2 each side) Z-stack inverted bushings connect the TTIs to the diodes. This paper will present and discuss all major aspects of the electrical and mechanical design, as well as the anticipated performance from circuit simulations. Prepared in collaboration with Leland Schlitt Consulting Services, WTP Engineering, Naval Research Laboratory, Science Applications International Corp., Commonwealth Technology Inc. and Research Support Instruments. Presented at 2003 IEEE Pulsed Power Conference (14th), PPC-2003, in Dallas, TX on 15-18 Jun 2003 and published in proceedings of the same, p551-554; 0-7803-7915-2/03. See also ADM002371, 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science.