Los Alamos National Laboratory / University of Washington

Field Reversed Configuration Collaboration

The MFE Team at Los Alamos is working with the University of Washington to demonstrate sustainment of the magnetic field (flux) of a Field Reversed Configuration (FRC) plasma. LANL has designed, built, tested, and shipped  two high power (60 Megawatts each) amplifiers which will power two Helmholtz coils on the outside of the "Translation, Confinement, and Sustainment" (or TCS) plasma at the Redmond Plasma Physics Lab, a few miles northeast of the University of Washington, in Seattle.

 Each system utilizes a bank of 6 parallel magnetically beamed ML8618 triodes. These devices are each rated at 250 Amperes cathode current and a 45 kV plate voltage. An advantage of the magnetically beamed triode is their extreme efficiency, requiring only 2.5 kW of filament and a few amps and a few kV of grid drive. We will operate them at a nominal 18 kV plate voltage, providing a 30 kV and 3000 Ampere peak to peak oscillation waveform, on the tube plates. Each drive coil set (3.5uH) is configured with an adjustable tank circuit (for tuning) and coupled through a 1:2 coaxial air-core balun auto-transformer. The auto-transformer provides DC isolation to the drive coils in addition to stepping up the coil drive voltage (to 60 kV pk-pk & 1500 A pk-pk). To control the ML8618's phase and amplitude, fast 150 Ampere "totem-pole" grid drivers, an "on" hot-deck and an "off" hot-deck, each with 6 parallel 3CPX1500A7's are used. By adjusting the conduction angle, amplitude may be regulated, with inter-pulse timing, phase angle can be controlled. A central feedback timing chassis monitors each systems' drive coils and appropriately derives each systems timing signals. Fiber-optic cables are used to isolate between the control room timing chassis and the remote power oscillator system. Performance characteristics have been computer modeled and tested in the lab. The system has been in routine operation for several years now.

A  set of Photos of the LANL Rotamak amplifiers during their construction is available (Thumbnail Index Page)

Last Updated: 07/18/06

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