Pulsed-power systems for the Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility

The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron linear induction accelerators to produce intense, bremsstrahlung X-ray pulses for flash radiography. The first DARHT accelerator became operational in July 1999 producing a single electron beam pulse at 20 MeV, 2 kA, and 60 ns pulse. The second DARHT accelerator consists of a 18.4 MeV, 2 kA, 2 microsecond pulse-width accelerator. Four short electron micropulses of variable pulse-width and spacing will be chopped out of the original, long accelerator pulse for producing time-resolved X-ray images. The first electron beam in this machine will be produced this year. We discuss the pulsed power systems associated with this machine. These include an injector driven by a Marx consisting of 88 type-E PFN stages driving a matched load at 3.2 MV with a 500 ns risetime, 2 microsecond e-beam pulse. The Metglas-filled induction cells making up the accelerator are described. Each induction cell is driven by a cell-driver that contains 4, 7-section E-network PFNs in a Marx configuration with a 20 Ω impedance that delivers flattop of greater than 2 microseconds into a resistive load of 5 Ω for a total drive current of 10 kA at 200 kV. The principal element of the electron beam transport system is the fast deflector, or kicker, used to generate four micropulses from the primary beam. The kicker modulator generates bi-polar 18 kV pulses of arbitrary pulse width and spacing using solid-state circuitry that is described. Component test data from the injector, accelerator, and kicker system is discussed.