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Description
The Los Alamos Neutron Science Center uses a coupled-cavity linac to accelerate H- ions from 100 to 800 MeV. It is powered by forty-four 1.25 MW 805 MHz klystrons, each capable of 150 kW of average power. A prototype solid-state amplifier that meets these requirements is in development. Commercial silicon LDMOS transistors have reduced power above 600 MHz and are also limited by the maximum drain to source breakdown voltage. We are using high voltage Gallium Nitride (GaN) on Silicon Carbide (SiC) high electron mobility transistors (HEMT) to reduce the number of active devices and the complexity of power combing smaller amplifiers. These wide bandgap semiconductors can operate at high channel temperatures around 200 degC without shortened life. We are testing new devices up 5 kW of peak power at 100 volts. Operating in saturation mode, outphasing modulation is used to maintain high device efficiency to reduce thermal dissipation, compared to conventional class AB linear amplifiers. The power supply requires stored energy with a capacitor bank. Power combining uses a combination of 2-way Gysel, 40-way radial and magic tee combiners in waveguide.
Funding Agency
Work supported by the U.S. Department of Energy through the Los Alamos National Laboratory, operated by Triad National Security, LLC, for the National Nuclear Security Administration (Contract No. 892
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