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 power two sets of saddle 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.

  We shipped the units to Seattle from Los Alamos (Nov. 8, 1999), and have installed them in the early months of 2000, and successfully begun plasma experiments, which are continuing.

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.

Presently we are working on prototyping, and designing twin 20-channel bolometers to be used in making radiation power balance measurements on TCS (7/31/03).

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

(click to see larger ones)

Twin Amplifier on wheels 10/28/97 4:40:26 PM	Front view of Rotamak amp 10/28/97 4:35:56 PM
Closeup view, showing 6 tube bases 10/28/97 4:35:10 PM	Rotamak capacitor bank.JPG 10/28/97 4:30:58 PM
Rotamak tube row and blowers 10/28/97 4:32:00 PM

Last Updated: 07/31/03