Nike - Pulseline And Diode Design For The 60 Cm Amplifier

An identical pair of pulsed power systems has been designed to drive the 60 cm aperture amplifier as part of the Naval Research Laboratory´s NIKE KrF laser system. The KrF gas volume is pumped from two opposite sides by 60 cm x 200 cm electron beams which are produced by two totally independent systems. Each pulse power system includes a /spl sim/240 kJ Marx, four (parallel) 5 ohm water filled coaxial pulseforming lines (PFLs), four laser triggered output switches and a monolithic, magnetic field immersed diode. Prominent design features include the large area of the water lines, 90/spl deg/ bcnds in the PFLs, radial-plastic output switch diaphragms (as in SUPER-SPRITE at RAL), and inside/out vacuum bushings (as in AURORA at LANL). Triggered diverters and various passive elements were designed to reduce damage in the event of a fault. A 4 ohm peaking section directly precedes the output switches to increase the flat top duration and an anode field shaper has been designed to reduce e-beam halo in the diode. Detailed circuit simulations show each system will produce a 700 keV, 100 kJ, 250 ns electron beam when driving a matched 1.25 ohm diode. Electrical stress and breakdown fractions were calculated throughout. The diode was modelled analytically and with an electron transport code. In the circuit code, the diode was represented by a Child-Langmuir model whose gap closes at 2.5 cm/ps. The transient response of the 900 bends in the PFLs was determined by a fully 3-D transmission line simulation as well as by a scaled analog model. Hardware fabrication is scheduled to begin in August 1991 with the goal of having one pulse power system (one-half the amplifier) operational by April 1992. The full 60 cm amplifier system is scheduled to be on-line by April 1993.